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Fish as Model Systems
Abstract
Fish represent the largest and most diverse group of vertebrates. Their evolutionary position relative to other vertebrates
and their ability to adapt to a wide variety of environments make them ideal for studying both organismic and molecular evolution.
A number of other characteristics make them excellent experimental models for studies in embryology, neurobiology, endocrinology,
environmental biology, and other areas. In fact, they have played a critical role in the development of several of these disciplines.
Research techniques that enable scientists to make isogenic lines in a single generation, create and maintain mutants, culture
cells, and transfer cloned genes into embryos signal an increasing role for fish as experimental models.
... Model organisms are easily raised in a laboratory setting and can usually tolerate a wide range of environmental conditions (White 2016). Additionally, there is typically a long history of in-breeding a single culture, resulting in highly homozygous strains and reduced individual variation between control animals (Powers 1989). Model fish species typically have a high fecundity rate, producing hundreds of eggs multiple times over the course of a year, which aids in their use for reproductive toxicity testing (Powers 1989). ...
... Additionally, there is typically a long history of in-breeding a single culture, resulting in highly homozygous strains and reduced individual variation between control animals (Powers 1989). Model fish species typically have a high fecundity rate, producing hundreds of eggs multiple times over the course of a year, which aids in their use for reproductive toxicity testing (Powers 1989). Examples of model fish species include Zebrafish, Japanese Medaka Oryzias latipes, Fathead Minnow Pimephales promelas, and Rainbow Trout (Carvan et al. 2007). ...
... For instance, they show direct pituitary innervation of hypophysiotropic neurons in the brain instead of mediating the hypothalamic-hypophyseal portal system (reviewed in (Zambrano 1972, Blázquez, Bosma et al. 1998) and their gonadotropins (luteinizing and follicle stimulating hormones) are produced in two separate cells in these animals (reviewed in (Weltzien, Hildahl et al. 2014)). Due to the high number of species (nearly 30 000 (Nelson, Grande et al. 2016)) and their high diversity (Volff 2005), these animals offer interesting models to investigate a wide range of biological questions (reviewed in (Powers 1989)). Moreover, due to their amenability to both laboratory and field experiments, teleosts offer many advantages compared to other organisms. ...
... Moreover, due to their amenability to both laboratory and field experiments, teleosts offer many advantages compared to other organisms. They are relatively inexpensive to purchase and maintain (reviewed in (Powers 1989, Harris, Henke et al. 2014). In particular, small teleost models, such as zebrafish and medaka, are species with very high fecundity and relatively short life cycle enabling rapid analysis of gene function and disease mechanisms , thus providing even greater advantages in addressing a plethora of biological and physiological questions, considering the numerous welldeveloped protocols and genetic tools available for these species (reviewed in (Briggs 2002, Naruse, Tanaka et al. 2011). ...
Sex steroids, produced by the gonads, play an essential role in the neuroendocrine control of reproduction in all vertebrates by providing feedback to the brain and pituitary. Sex steroids also play an important role in tissue plasticity by regulating cell proliferation in several tissues including the brain and the pituitary. Therefore, investigating the role of sex steroids and mechanisms by which they act is crucial to better understand both feedback mechanism and tissue plasticity. Teleost fish, which possess a higher degree of tissue plasticity and variations in reproduction strategies compared to mammals, appear to be useful models to investigate these questions. The removal of the main source of sex steroid production using gonadectomy together with blood sampling to measure steroid levels, have been well-established and fairly feasible in bigger fish and are powerful techniques to investigate the role and effects of sex steroids. However, small fish such as zebrafish and medaka, which are particularly good model organisms considering the well-developed genetic toolkit and the numerous protocols available to investigate their biology and physiology, raise challenges for applying such protocols due to their small size. Here, we demonstrate the step-by-step procedure of gonadectomy in both males and females followed by blood sampling in a small sized teleost model, the Japanese medaka ( Oryzias latipes ). The use of these procedures combined with the other advantages of using these small teleost models will greatly improve our understanding of feedback mechanisms in the neuroendocrine control of reproduction and tissue plasticity provided by sex steroids in vertebrates.
SUMMARY
The article describes a quick protocol to gonadectomize and sample blood from small teleost fish, using medaka ( Oryzias latipes ) as a model, to investigate the role of sex steroids in animal physiology.
... Significant differences in survival rates were calculated with the Tukey multiple comparisons test. Correlation and principal components analysis were performed with STAT-ITCF (1987-19SS) and SYSTAT for Windows softwares (1992). ...
... STAT-ITCF (1987 sysTAT for windows. (1992). Version 5.0. ...
La mise sur le marché de nouvelles molécules ou procédés nécessite au préalable des essais de laboratoire permettant d'évaluer leur potentiel toxique intrinsèque et les risques liés à leur utilisation à l'échelle industrielle. Une synthèse bibliographique expose les principales connaissances sur les biosalissures aquatiques et les traitements utilisés ou préconisés pour les contrôler en milieu industriel. Une étude expérimentale est consacrée aux effets létaux d'un nouvel agent anti-salissures: le Mexel 432 vis-à-vis du développement embryo-larvaire de la carpe commune, choisie comme modèle écotoxicologique. Les principales caractéristiques du Mexel 432 et du modèle embryon de carpe sont présentées. Dans une eau synthétique, en exposition continue depuis la fécondation, sans apport alimentaire, les CL50 moyennes mesurées sur plusieurs pontes sont 1,13+-0,35 mg/L après 3 jours d'exposition, 0,88+-0,36 après 7 jours et 0,69+-0,32 après 9 jours. Les CL50 (7 jours) la plus basse et la plus élevée sont 0,34 et 1,58 mg/L. En concentrations sublétales, la croissance embryo-larvaire est diminuée. Une étude histopathologique semble montrer une dégénérescence de l'épithélium branchial larvaire. Dans des échantillons d'eau de rivières, la toxicité est immédiatement diminuée en relation avec une demande immédiate en Mexel 432 liée à son adsorption sur les matières en suspension (argiles) ou à sa complexation avec des matières organiques dissoutes (acides humiques). La toxicité du Mexel 432 est déterminée pour l'essentiel par son contenu en amines grasses. L'adjonction d'un antigel inhibe le collage des oeufs, le principe d'une méthode de quantification de cet effet étant propose. La température, le pH et la concentration en calcium ont peu d'effets sur la toxicité du Mexel 432. Celui-ci a peu d'influence sur la toxicité de divers xénobiotiques de degrés d'hydrophobie variés. L'utilisation d'une méthode standardisée par EDF (dosage colorimétrique à l'orange de méthyle en milieu acide), a permis d'atteindre en eau de laboratoire des seuils de détection et de mesure de 0,29 et 0,58 mg/L en Mexel 432, la pente de la droite d'étalonnage dans la gamme de concentration 0,1 - 12,8 mg/L étant 18,02+-0,22
... Fish have evolved some of the most diverse life history traits of all animals, allowing them to inhabit a wide range of environments (Cossins and Crawford, 2005;Powers, 1989) and in some species, these traits can facilitate resiliency to natural and anthropogenic disturbances (Allendorf and Hard, 2009;Candolin, 2009;Schweikert and Grace, 2018). With the high potential for adaptation, these traits have been an important focus of evolutionary ecologists (e.g., Stearns, 1977), and for predicting how fish will respond to rapid environmental change in the Anthropocene (Kindsvater et al., 2016;Villéger et al., 2017). ...
... The understanding of toxicant uptake, behavior, and responses in fish may, therefore, have a high ecological relevance (Espino, 2000). They are good model for the studies involving biochemistry, physiology and cellular studies which can be easily reproduced under laboratory condition (Powers, 1989). Thus fishes are well recognized bioindicators of environmental changes including chemical or industrial effluents pollution. ...
... The understanding of toxicant uptake, behavior, and responses in fish may, therefore, have a high ecological relevance (Espino, 2000). They are good model for the studies involving biochemistry, physiology and cellular studies which can be easily reproduced under laboratory condition (Powers, 1989). Thus fishes are well recognized bioindicators of environmental changes including chemical or industrial effluents pollution. ...
... The understanding of toxicant uptake, behavior, and responses in fish may, therefore, have a high ecological relevance (Espino, 2000). They are good model for the studies involving biochemistry, physiology and cellular studies which can be easily reproduced under laboratory condition (Powers, 1989). Thus fishes are well recognized bioindicators of environmental changes including chemical or industrial effluents pollution. ...
... They serve as bioindicators of environmental pollution because of their link in the food chain (Lopes et al., 2001). Fish also serve as a major test organism and are particularly useful for the assessment of waterborne and sediment deposited toxins where they may provide advanced warning of the potential danger of new chemicals and the possibility of environmental pollution (Powers, 1989). Accumulation of ZnO-NPs in the tissue of fish may reduce the nutritional value, thus contamination of water bodies where fish reside deserve greater attention. ...
Zinc Oxide nano-particles (ZnO-NPs) are more useful in the production of commercial goods than other nano-particles because of their unique properties. The effluents of ZnO-NPs get into the aquatic ecosystems and accumulate in fish tissues causing serious health consequences. This study was therefore designed to investigate the effect of ZnO-NPs exposure on the nutritional composition and depuration potential of large African catfish (Heterobranchus longifilis). The nutritional composition evaluated include, proximate composition, mineral content, fatty acids and amino acids profiles after exposing to varying (0.0, 6.00, 8.00, 10.00, 12.00 mg/l) concentrations of ZnO-NPs to juveniles’ catfish (H. longifilis) for 60 days and depurating for 30 days to evaluate recovery using standard methods. The results revealed that proximate composition and amino acid profiles decreased significantly (P < 0.05) after 60 days of exposure to ZnO-NPs, but gradually improved after 30 days of depuration. This implies that ZnO-NPs has a great influence on the nutrient values of H. longifilis, but the fish were able to regain the lost nutrients, however, the ability of H. longifilis to recover from adverse condition is time dependent.
... The understanding of toxicant uptake, behavior, and responses in fish may, therefore, have a high ecological relevance (Espino, 2000). They are good model for the studies involving biochemistry, physiology and cellular studies which can be easily reproduced under laboratory condition (Powers, 1989). Thus fishes are well recognized bioindicators of environmental changes including chemical or industrial effluents pollution. ...
The full-length chapter titled, 'A detailed study of the effect of SARS-COV-2 vaccines on HIV patients' is published in the book 'Emerging Infectious COVID-19 and Zoonotic diseases: Causes and Therapeutic approaches' as a proceeding of the International Virtual Seminar on Recent Trends in Life Sciences and Biotechnology, 5th Annual Meeting of International Association of Zoologists held from 12th to 18th December 2021.
... The understanding of toxicant uptake, behavior, and responses in fish may, therefore, have a high ecological relevance (Espino, 2000). They are good model for the studies involving biochemistry, physiology and cellular studies which can be easily reproduced under laboratory condition (Powers, 1989). Thus fishes are well recognized bioindicators of environmental changes including chemical or industrial effluents pollution. ...
On the occasion of 290th Birth Anniversary celebration of Hon’ble Erasmus
Darwin, the Department of Biotechnology, MM(DU) is going to organize ‘5th
Annual meeting of IAZ’ and ‘2nd International Virtual Seminar on Recent
Trends in Life Sciences and Biotechnology’ on focal theme “Strategies to
Combat COVID-19, Zoonoses and Other Communicable Diseases” during 12-18
December, 2021). The seminar will provide a common platform for distinguished
scientists, researchers, postgraduate and undergraduate students to understand,
discuss and debate over the new developments and scientific advancements
that will impact future strategies to intervene with current COVID-19 pandemic,
zoonoses and various communicable diseases in human beings, ranging from
a mechanistic understanding to prevention, diagnosis, treatment, prognosis,
therapy, response monitoring and eradication. This virtual venture will give
opportunity to young researchers to present their innovative ideas and finding
in the form of e-oral presentation or e-poster presentation in the young scientist
categories in front of the scientific community which will be more interactive
during special discussion with stalwarts and eminent personalities. The invited
Chief Guest, Guests of Honour, Special Guests, Invited speakrs, delegates,
young scientists, research sclolars and students of about 21 countries, 25 states,
and over 40 universities have showed their interest for active participation. The
organizing committee feel immense pleasure to welcome one and all on this
vitual venture and thankful to every one for making the event a Grand success.
... Plasma enzyme levels in fish are good indicators of extreme stress and provide information of organ dysfunction (Wells et al., 1986;Jiminez and Stegeman, 1990). As such, biochemical and physiological indicators such as enzymes could be used (as biomarkers) to identify possible environmental contamination before the health of aquatic organisms is seriously affected (Barnhoorn and Van Vuren, 2004;Powers, 1989 &Pickering andPottinger, 1995). Biochemical approach has been advocated to provide an early warning of potentially damaging changes in stressed fish (Casillas et al., 1983). ...
Present study was undertaken to study the alterations in blood biochemical indices due to the presence of helminth parasites in Schizothorax and carp fishes collected from Dal and Anchar lakes of Kashmir. The prevalence of parasites and other indices were assessed and compared with the alterations in the serum biochemical indices of infected as well as uninfected fishes. During the investigation three helminth parasites viz. Pomphorhyncus, Neoechinorhyncus and Adenoscolex were recovered from the infected fish specimens examined. The overall prevalence of parasites in Schizothorax and carps of Dal Lake was 48.54% and 41.23% respectively, while as in Anchar Lake, it was 53.70% and 50.50% respectively. In Dal Lake, among Schizothorax fishes the highest prevalence was of Pomphorhyncus parasite (26.21%) followed by Neoechinorhyncus (19.42%) and Adenoscolex (15.53%). In case of carp fishes the order was Neoechinorhyncus (21.93%) followed by Pomphorhyncus (19.30%) and Adenoscolex (14.04%). In Anchar lake, the highest prevalence among the parasites in Schizothorax fishes was of Pomphorhyncus (27.78%) followed by Neoechinorhyncus (24.07%) and Adenoscolex (18.52%). The carp fishes followed a different pattern, the most prevalent parasite being Pomphorhyncus (22.77%) followed by Adenoscolex (19.80%) and Neoechinorhyncus (15.84%). The blood biochemical indices were found altered in parasitized fishes as compared to those of non-parasitized fishes in both the water bodies. Total protein, albumin and bilirubin of infected fishes showed a significant decrease compared to uninfected ones. Globulins, glucose, AST, ALP, and LDH showed a significant increase in infected fishes when compared to uninfected fishes. Significant differences were found between them as regards the alteration in blood biochemical parameters signifying higher eutrophication status of Anchar Lake due to increased levels of pollution as a result of heavy inflow of nutrients and sewage coming out either from SKIMS or households. These stress conditions make fishes more susceptible to parasitic infections. Moreover, Schizothorax fishes being more sensitive than carp fishes are more prone to parasitic infections hence depict higher alterations in blood biochemical indices than carp fishes.
... Even before the genome sequencing era, fish species were explored as model organisms in biological research using different molecular biology techniques (Powers 1989). Molecular genetics and genome research were the main areas of interest for biologists to consider fishes as models among other vertebrates. ...
The living fishes span a unique and interesting set of animals because of their vast diversity, morphology, ecology, genetics and genomics, and higher importance to biology, economy and culture. During the past decade, the remarkable increase in fish genome sequencing has revolutionized comparative and evolutionary genomics, with the outcome of stimulating insights into vertebrate genome biology. Fish genomics has been transformed rapidly, with the availability of high-quality chromosome level genome assemblies and large collections of sequencing datasets, which are roadmaps for striking discoveries. Landmark achievements are being made; such as the accomplishment of fully assembled lungfish genome which is biggest genome ever sequenced. Here, we highlight current developments in vertebrate’s comparative genomics and discuss how fish genomes could be considered as vital resources for genomic studies. We present a recent overview of genomics data, address different approaches applicable to comparative genomics analyses, and illustrate these comparisons to better understand the complex mechanisms under the vertebrate genomes. We also summarize the applications in chromosomes research and cytogenomics.
Graphic abstract
... Even before the genome sequencing era, fish species were explored as model organisms in biological research using different molecular biology techniques (Powers 1989). Molecular genetics and genome research were the main areas of interest for biologists to consider fishes as models among other vertebrates. ...
The living fishes span a unique and interesting set of animals because of their vast diversity, morphology, ecology, genetics and geno-mics, and higher importance to biology, economy and culture. During the past decade, the remarkable increase in fish genome sequencing has revolutionized comparative and evolutionary genomics, with the outcome of stimulating insights into vertebrate genome biology. Fish genomics has been transformed rapidly, with the availability of high-quality chromosome level genome assemblies and large collections of sequencing datasets, which are roadmaps for striking discoveries. Landmark achievements are being made; such as the accomplishment of fully assembled lungfish genome which is biggest genome ever sequenced. Here, we highlight current developments in vertebrate's comparative genomics and discuss how fish genomes could be considered as vital resources for genomic studies. We present a recent overview of genomics data, address different approaches applicable to comparative genomics analyses, and illustrate these comparisons to better understand the complex mechanisms under the vertebrate genomes. We also summarize the applications in chromosomes research and cytogenomics. Supplementary Information The online version contains supplementary material available at https://doi.
... Fishes are the most diverse and abundant group of vertebrates in the world (Powers 1989;Ravi & Venkatesh 2008), making up nearly 50 % of all vertebrate diversity. Further, fishes are important keystone species in many ecosystems and exhibit diverse behaviours and ecologies (Spencer & King 1984;Allan 2004;Dudgeon et al. 2006;Wu et al. 2014). ...
The fish fauna of the Kabul River downstream of the City of Kabul face threats from increasing human population such as pollution, overfishing, and increased development. Despite the rapid increase of these activities leading to threats to fishes in the Kabul River, no studies have examined the changes in diversity, distribution, and abundance of fish fauna in the Kabul River surrounding of Kabul City. In this study, the Kabul River was divided into two zones (upstream and downstream) consisting of six sampling sites (3 sites per zone). Of the total of 1,190 fishes collected, Cypriniformes was the dominant order with one family, six genera, and eight species. Cyprinidae was the dominant family of that order with 81.4% (n= 969) of total individuals. Species abundance was higher in the upstream reaches in almost all analyses. Upstream sites recorded 11 species, while seven species were recorded from downstream sites. Fish species richness was significantly higher upstream versus downstream reaches (9.67 ± 1.53 vs. 6.33 ± .58; U= .00, z= -1.99, p= .04, r= .81). Species diversity upstream was significantly higher than downstream (H’= 1.90 ± 0.15, D1= 0.81 ± 0.02). Similarly, species evenness was also higher upstream than downstream (J’= 0.84 ± 0.01). Low diversity, abundance, and evenness in downstream reaches are likely due to anthropogenic activities affecting the river in and around Kabul City.
... Fishes are the most diverse and abundant group of vertebrates in the world (Powers 1989;Ravi & Venkatesh 2008), making up nearly 50 % of all vertebrate diversity. Further, fishes are important keystone species in many ecosystems and exhibit diverse behaviours and ecologies (Spencer & King 1984;Allan 2004;Dudgeon et al. 2006;Wu et al. 2014). ...
The fish fauna of the Kabul River downstream of the City of Kabul face threats from increasing human population such as pollution, overfishing, and increased development. Despite the rapid increase of these activities leading to threats to fishes in the Kabul River, no studies have examined the changes in diversity, distribution, and abundance of fish fauna in the Kabul River surrounding of Kabul City. In this study, the Kabul River was divided into two zones (upstream and downstream) consisting of six sampling sites (3 sites per zone). Of the total of 1,190 fishes collected, Cypriniformes was the dominant order with one family, six genera, and eight species. Cyprinidae was the dominant family of that order with 81.4% (n= 969) of total individuals. Species abundance was higher in the upstream reaches in almost all analyses. Upstream sites recorded 11 species, while seven species were recorded from downstream sites. Fish species richness was significantly higher upstream versus downstream reaches (9.67 ± 1.53 vs. 6.33 ± .58; U= .00, z= -1.99, p= .04, r= .81). Species diversity upstream was significantly higher than downstream (H’= 1.90 ± 0.15, D1= 0.81 ± 0.02). Similarly, species evenness was also higher upstream than downstream (J’= 0.84 ± 0.01). Low diversity, abundance, and evenness in downstream reaches are likely due to anthropogenic activities affecting the river in and around Kabul City.
... Fish are susceptible to genetic effects induced by xenobiotics (Belfiore and Anderson 2001;Cajaraville et al. 2003), and their metabolic systems and defense mechanisms respond similarly to other vertebrates (Stegeman and Lech 1991). Therefore, despite some limitation, fish are considered very proper experimental models in several different research areas (Powers 1989). Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution in freshwater and marine water bodies (Hawkins et al. 1988;Dashwood and Bailey 1998;Ohe et al. 2004;Monserrat et al. 2007;Colin et al. 2016;Kroon et al. 2017). ...
Harmful cyanobacterial blooms are increasing and becoming a worldwide concern as many bloom-forming cyanobacterial species can produce toxic metabolites named cyanotoxins. These include microcystins, saxitoxins, anatoxins, nodularins, and cylindrospermopsins, which can adversely affect humans, animals, and the environment. Different methods to assess these classes of compounds in vitro and in vivo include biological, biochemical, molecular, and physicochemical techniques. Furthermore, toxic effects not attributable to known cyanotoxins can be observed when assessing bloom material. In order to determine exposures to cyanotoxins and to monitor compliance with drinking and bathing water guidelines, it is necessary to have reliable and effective methods for the analysis of these compounds. Many relatively simple low-cost methods can be employed to rapidly evaluate the potential hazard. The main objective of this mini-review is to describe the assessment of toxic cyanobacterial samples using in vitro and in vivo bioassays. Newly emerging cyanotoxins, the toxicity of analogs, or the interaction of cyanobacteria and cyanotoxins with other toxicants, among others, still requires bioassay assessment. This review focuses on some biological and biochemical assays (MTT assay, Immunohistochemistry, Micronucleus Assay, Artemia salina assay, Daphnia magna test, Radionuclide recovery, Neutral red cytotoxicity and Comet assay, Enzyme-Linked Immunosorbent Assay (ELISA), Annexin V-FITC assay and Protein Phosphatase Inhibition Assay (PPIA)) for the detection and measurement of cyanotoxins including microcystins, cylindrospermopsins, anatoxin-a, saxitoxins, and nodularins. Although most bioassay analyses often confirm the presence of cyanotoxins at low concentrations, such bioassays can be used to determine whether some strains or blooms of cyanobacteria may produce other, as yet unknown toxic metabolites. This review also aims to identify research needs and data gaps concerning the toxicity assessment of cyanobacteria.
... Fish are susceptible to genetic effects induced by xenobiotics (Belfiore and Anderson 2001;Cajaraville et al. 2003), and their metabolic systems and defense mechanisms respond similarly to other vertebrates (Stegeman and Lech 1991). Therefore, despite some limitation, fish are considered very proper experimental models in several different research areas (Powers 1989). Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution in freshwater and marine water bodies (Hawkins et al. 1988;Dashwood and Bailey 1998;Ohe et al. 2004;Monserrat et al. 2007;Colin et al. 2016;Kroon et al. 2017). ...
Cadmium (Cd) has been widely studied as an environmental pollutant for many years. Numerous studies have reported that Cd exposure causes damage to the heart, liver, kidneys, and thyroid in vivo. The emerging evidence suggests that Cd exposure induces damage on male reproductive system, which is related to oxidative stress, inflammation, steroidogenesis disruption, and epigenetics. Current preclinical animal studies have confirmed a large number of proteins and intracellular signaling pathways involved in the pathological process of Cd-induced male reproductive damage and potential measures for prophylaxis and treatment, which primarily include antioxidants, anti-inflammatory agents, and essential ion supplement. However, explicit pathogenesis and effective treatments remain uncertain. This review collects data from the literatures, discusses the underlying mechanisms of Cd-induced toxicity on male reproductive function, and summarizes evidence that may provide guidance for the treatment and prevention of Cd-induced male reproductive toxicity.
... Fish are susceptible to genetic effects induced by xenobiotics (Belfiore and Anderson 2001;Cajaraville et al. 2003), and their metabolic systems and defense mechanisms respond similarly to other vertebrates (Stegeman and Lech 1991). Therefore, despite some limitation, fish are considered very proper experimental models in several different research areas (Powers 1989). Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution in freshwater and marine water bodies (Hawkins et al. 1988;Dashwood and Bailey 1998;Ohe et al. 2004;Monserrat et al. 2007;Colin et al. 2016;Kroon et al. 2017). ...
Safeners are a group of chemicals applied with herbicides to protect crop plants from potential adverse effects of agricultural products used to kill weeds in monocotyledonous crops. Various routes of dissipation of safeners from their point of applications were evaluated. Despite the large numbers of safeners (over 18) commercially available and the relatively large quantities (~2 × 106 kg/year) used, there is little information on their mobility and fate in the environment and occurrence in various environmental matrices. The only class of safeners for which a significant amount of information is available is dichloroacetamide safeners, which have been observed in some rivers in the USA at concentrations ranging from 42 to 190 ng/L. Given this gap in the literature, there is a clear need to determine the occurrence, fate, and bioavailability of other classes of safeners. Furthermore, since safeners are typically used in commercial formulations, it is useful to study them in relation to their corresponding herbicides. Common routes of dissipation for herbicides and applied safeners are surface run off (erosion), hydrolysis, photolysis, sorption, leaching, volatilization, and microbial degradation. Toxic potencies of safeners vary among organisms and safener compounds, ranging from as low as the LC50 for fish (Oncorhynchus mykiss) for isoxadifen-ethyl, which was 0.34 mg/L, to as high as the LC50 for Daphnia magna from dichlormid, which was 161 mg/L. Solubilities and octanol-water partition coefficients seem to be the principal driving force in understanding safener mobilities. This paper provides an up-to-date literature review regarding the occurrence, behaviour, and toxic potency of herbicide safeners and identifies important knowledge gaps in our understanding of these compounds and the potential risks posed to potentially impacted ecosystems.
... In addition, many are not completely removed by sewage treatment plants (Bolong et al. 2009). These contaminants then reach aquatic ecosystems and are freely bioavailable to the local biota, resulting in both ecological and human health concerns, as many species also play an extremely important ecological role in aquatic trophic webs as energy carriers at higher trophic levels, being important links between the environment, contaminants and human populations (Espino 2000;Powers 1989). In this context, it is noteworthy that demands on the exploitation of fishing resources in coastal regions has increased worldwide (FAO 2018), and estimates indicate that about 75% of the world's population will be living in coastal zones in 2025 (Cohen 1995). ...
During the months of January and November 2011 were captured eight dolphins (four females and four males) in Laguna de Terminos, Campeche, Mexico in order to take samples for health and for use with a satellite transceiver. Transmitters were used Wildlife Computers Company Model MK -10, specially designed to be placed in medium sized dolphin. It was tracking the movements of individuals over a period of two to four weeks showing a main mobility in the north-central part of the lagoon of terms and only a few males left the lagoon off the Gulf of Mexico for a short time. Seven of the eight subjects had adequate health status to the wild and only the longest female presented skin lesions caused by infectious agents (bacteria or viruses possibly), and several shark bite scars. It seems that neither the stress of capture and handling of animals led to abandon their usual areas. It was found that females use a larger area for their activities (of 260-340 km2), whereas in this area males ranged from 120 to 350 km2. The high site fidelity observed, showing that these individuals know the area they inhabit taking advantage of conditions Laguna de Terminos offers to meet their needs for food, shelter and reproduction. This is the first scientific catch of the species in the southern Gulf of Mexico to the use of satellite transmitters.
... In addition, many are not completely removed by sewage treatment plants (Bolong et al. 2009). These contaminants then reach aquatic ecosystems and are freely bioavailable to the local biota, resulting in both ecological and human health concerns, as many species also play an extremely important ecological role in aquatic trophic webs as energy carriers at higher trophic levels, being important links between the environment, contaminants and human populations (Espino 2000;Powers 1989). In this context, it is noteworthy that demands on the exploitation of fishing resources in coastal regions has increased worldwide (FAO 2018), and estimates indicate that about 75% of the world's population will be living in coastal zones in 2025 (Cohen 1995). ...
... 7−10 Fish constitute an important, economical, and diverse group in both freshwater and marine food webs. 11 Meanwhile, some of them are often used as bioindicators for ecosystem health because of their sensitivity to many toxicants. 12 The behavioral responses of fish to ecosystem alteration, including the presence of microplastics have been widely studied. ...
... Of the main vertebrate groups, fishes have occupied the planet for the longest period of time, and have the highest diversity present in the backboned-animal kingdom (Powers 1989). This has led to the development of a wealth of tail, or caudal fin, forms and functions. ...
Fishes are the longest persisting living vertebrates and as such, display an incredible array of diversity. Variation in the tail, or caudal fin, is often a reflection of a fish's environment, and affects movement, predation, defense, and reproduction. Previous literature has discussed many aspects of caudal fin form and function in particular taxonomic groups; however, no previous work has synthesized these studies in order to detail how the caudal fin is structured, and what purpose this structure serves, throughout the phylogeny of fishes. This review examines the caudal fin throughout the main lineages of fish evolution, and highlights where changes in shape and usage have occurred. Such novelties in form and function tend to have far-reaching evolutionary consequences. Through integration of past and present work, this review creates a coherent picture of caudal fin evolution. Patterns and outliers that demonstrate how form and function of this appendage are intertwined can further inform hypotheses that fill critical gaps in knowledge concerning the caudal fin.
... Fishes represent important laboratory animals, with increasing numbers of species used as model organisms in research (Braasch et al., 2015;Laland et al., 2011;Powers, 1989;Schartl, 2014;Utne-Palm & Smith, 2020). Increasing the diversity of model organisms can be a boon for research (Alfred & Baldwin, 2015) and fishes, as the most numerous group of vertebrates, are of interest to many researchers. ...
Growing research effort has shown that physical enrichment (PE) can improve fish welfare and research validity. However, the inclusion of PE does not always result in positive effects and conflicting findings have highlighted the many nuances involved. Effects are known to depend on species and life stage tested, but effects may also vary with differences in the specific items used as enrichment between and within studies. Reporting fine‐scale characteristics of items used as enrichment in studies may help to reveal these factors. We conducted a survey of PE‐focused studies published in the last 5 years to examine the current state of methodological reporting. The survey results suggest that some aspects of enrichment are not adequately detailed. For example, the amount and dimensions of objects used as enrichment were frequently omitted. Similarly, the ecological relevance, or other justification, for enrichment items was frequently not made explicit. Focusing on ecologically relevant aspects of PE and increasing the level of detail reported in studies may benefit future work and we propose a framework with the acronym DETAILS (Dimensions, Ecological rationale, Timing of enrichment, Amount, Inputs, Lighting and Social environment). We outline the potential importance of each of the elements of this framework with the hope it may aid in the level of reporting and standardization across studies, ultimately aiding the search for more beneficial types of PE and the development of our understanding and ability to improve the welfare of captive fish and promote more biologically relevant behaviour.
... Faced with global change, water temperature is gradually rising, consequently affecting the biodiversity of aquatic organisms. Survival in this situation requires an appropriate response and adaptation (Cossins and Crawford 2005;Powers 1989). Fishes have developed physiological and biochemical responses to heat stressors depending on their magnitude and duration, such as primary (initial neuroendocrine responses), secondary (metabolism, acid-base status, immune function, and cellular responses), and tertiary (changes in the whole animal performance such as growth, disease resistance, and feeding) (Barton 2002;Cossins et al. 2002). ...
Background
The olive flounder (Paralichthys olivaceus) is a saltwater fish, which is valuable to the economy. The olive flounder strives to adapt to environmental stressors through physiological, biochemical, and transcriptional responses. The rise in water temperature threatens the growth, development, reproduction, and survival of olive flounder. Each organ in the olive flounder can differentially respond to heat stress.Objectives
The purpose of this study is to investigate organ-specific transcriptional changes in olive flounder tissues during heat stress.Methods
In this study, transcriptome dynamics of the gill, liver, and muscle of olive flounder to acute or chronic heat stress were investigated.ResultsPrincipal component analysis plotting revealed that the transcriptome of each organ is quite separated. K-means clustering, gene ontology, and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed the differential transcriptome responses of each organ to heat stress. Heat stress commonly affects the pathways involved in the correct protein folding, DNA repair, and cell cycle.Conclusion
Our results may provide a valuable molecular basis of heat acclimation in fishes.
... They make up more than one-half of all vertebrate species (+32 000), in fact more than all the other classes combined (+60 000) [1]. Perhaps a dozen or so of these fish species are of particular interest with respect to the field of laboratory animal models [2]. Amphibians arose around 370 million years ago and include around 7000 species, of which only a few are commonly found in this field [3]. ...
The use of aquatic animals in ecotoxicology, genetic, and biomedical research has grown immensely in recent years, especially due to the increased use of zebrafish in the laboratory setting. Because water is the primary environment of most aquatic species, the composition and management of this water is paramount to ensuring their health and welfare. In this publication, we will describe the important variables in water quality that can influence animal health and research results, using the zebrafish model for detailed specifics of optimal conditions. Wherever possible, recommendations are provided to reduce the potential impact of poor or highly variable water quality, and standards are given which can be used as institutional goals to maximize animal health and welfare and reduce research variability. It is increasingly important that authors of publications describing work done using aquatic models characterize water quality and other environmental conditions of the animal environment so that the work can be repeated and understood in context of these important factors. It is clear that there are a great many extrinsic factors which may influence research outcomes in the aquatics model laboratory setting, and consequently, an increased level of funding will be essential to support continued research exploring these and other important husbandry conditions. References from a large body of literature on this subject are provided.
... In some applications, such as assessment of toxicity associated with exposure to complex chemical mixtures or in low-dose chronic exposure regimens, fish are recognized as test organisms with distinct and superior benefits in providing insights to disease processes. [19] Fish are also embraced as cost-effective and important animal models in genetics, developmental biology and toxicology. [10] Development of transgenic fish has been envisioned as a means to enhance the utility of fish models in reducing, refining, or replacing selected mammals used in toxicity testing or in biological research, as a whole. ...
Fish have played significant roles in assessing potential risks associated with exposure to chemical contamination in aquatic environments. Considering the contributions of transgenic rodent models to biomedicine, it has been noted that the development of transgenic fish may have significant role of fish in a variety of biological research. Hence, transgenic fish in experimental studies has been recently introduced as new model and method for research. Rapid advances are most evident in the area of in vivo mutagenesis using fish carrying transgenes that serve as recoverable mutational targets. These models highlight many advantages afforded by fish as models and illustrate important issues that apply broadly to transgenic fish in bioscience. Researchers have revealed that fish exhibit frequencies of spontaneous mutations similar to rodents and respond to mutagen exposure consistent with known mutagenic mechanisms. Results have shown the feasibility of in vivo mutation analyses using transgenic fish and have illustrated their potential value as a comparative animal model. Challenges to development and application of transgenic fish relate to the needs for improved efficiencies in transgenic technology and fish husbandry. Thus, it seems that transgenic fish will make significant contributions in biological research.
... Enzyme activities are considered as sensitive biochemical indicators before hazardous effects occur in fish and so they are important parameters for testing water for the presence of toxicants 7 . Biochemical and physiological indicators such as enzymes, could be used (as biomarkers) to identify possible environmental contaminations before the health of aquatic organisms is seriously affected 8,9 and to develop water quality indices [10][11][12][13][14] . ...
In the present study, we investigated the biochemical constitutes of blood serum of two fish Lerthinus harak and Terapon jarbua from two stations (Al-Kumrah and Al-Shoaibah) in the Jeddah District along Saudi Arabia Red Sea Coast at summer season 2014. The biochemical constitutes were found to be altered in Al-Kumrah area with a decrease in glucose, total protein and triglyceride concentrations, indicating a possible case of losing blood to the tissues or inefficiency in liver function, While an increase in urea concentration in fish collected from Al-Kumrah area indicating a possible case of inefficiency in kidney function, and this location were significantly different (p ≤ 0.01) with Al-Shoaibah site. The serum aspartate transaminase (AST), alanine transaminase (ALT) activities, alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT)showed a significant increase in fish, collected from Al-Kumrah site, indicating to the hepatocellular damage, and this location was significantly different (p ≤ 0.01) with Al-Shoaibah site. These results suggest that the fish collected from Al-Kumrah site might be considered relatively polluted with heavy metals. Thus, we may conclude that the altered activities of biochemical parameters could be useful biomarkers of water pollution.
... Enzyme activities are considered as sensitive biochemical indicators before hazardous effects occur in fish and so they are important parameters for testing water for the presence of toxicants 7 . Biochemical and physiological indicators such as enzymes, could be used (as biomarkers) to identify possible environmental contaminations before the health of aquatic organisms is seriously affected 8,9 and to develop water quality indices [10][11][12][13][14] . ...
In the present study, we investigated the biochemical constitutes of blood serum of two fish Lerthinus harak and Terapon jarbua from two stations (Al-Kumrah and Al-Shoaibah) in the Jeddah District along Saudi Arabia Red Sea Coast at summer season 2014. The biochemical constitutes were found to be altered in Al-Kumrah area with a decrease in glucose, total protein and triglyceride concentrations, indicating a possible case of losing blood to the tissues or inefficiency in liver function, While an increase in urea concentration in fish collected from Al-Kumrah area indicating a possible case of inefficiency in kidney function, and this location were significantly different (p ≤ 0.01) with Al-Shoaibah site. The serum aspartate transaminase (AST), alanine transaminase (ALT) activities, alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT)showed a significant increase in fish, collected from Al-Kumrah site, indicating to the hepatocellular damage, and this location was significantly different (p ≤ 0.01) with Al-Shoaibah site. These results suggest that the fish collected from Al-Kumrah site might be considered relatively polluted with heavy metals. Thus, we may conclude that the altered activities of biochemical parameters could be useful biomarkers of water pollution.
... Fish are widely used as sentinels for aquatic ecosystem pollution stemming from chemical exposure and are the preferred model for development of chemical testing guidelines (10,11). Among others, their practical relevance are based on: (i) wide distribution in aquatic environments; (ii) high ecological relevance due to position within food web structure, nutrient cycling and energy transfer; and (iii) expanding models and tools that researchers can use (12). ...
The alarming growth of the world’s population is putting ever-greater demand on agricultural industries and is manifesting in environmentally detrimental consequences. While the development of better aquaculture practices presents a promising means of meeting the needs of this population growth, overcrowding in aquaculture, climate change, and habitat destruction are
resulting in the emergence of new and opportunistic infections within farmed and wild aquatic vertebrate species, often to the detriment of these animals. The prevention and circumvention of these infections and die-offs requires much greater understanding of the mechanisms by which these animals’ immune systems develop, recognize, and respond to distinct pathogens. Indeed, we already know that while animals like cartilaginous/bony fish and amphibians exhibit hallmark components associated with mammalian immunity, they also provide examples of novel strategies for immune cell development and antimicrobial defenses. As these organisms possess arguably less developed adaptive immune responses, they rely more heavily on their innate immunity to control infiltrating pathogens. In turn, these animals reside in vastly distinct environments to those within which (the much more extensively characterized) mammalian immune system has evolved, so it
is not surprising that aquatic vertebrates possess many intriguing immunological differences from terrestrial animals. It is by gaining greater insight into these immune processes that we may hope to better our
aquacultural practices and combat the devastating effects of human activities on aquatic animal communities around the globe. Toward this end and through this collection of 17 articles, which include both original research as well as comprehensive reviews, we coalesce recent advances in the current understanding of the innate immune responses of aquatic vertebrates.
... Bioindikátory" jsou organismy, které reagují na znečištění životního prostředí změnou životních funkcí nebo akumulací toxinů v jejich těle. V poslední době přilákaly velkou pozornost při posuzování kvality životního prostředí ryby(Powers 1989, Zhou et al. 2008). Lze je nalézt prakticky všude ve vodním prostředí a hrají významnou ekologickou úlohu v potravním řetězci jako nosiči energie z nižší na vyšší trofické úrovně(Beyer 1996, Zhou et al. 2008) a mohou mít i přímý vliv na člověka jako D r a f t 0 2 potenciálního konzumenta (Zhou et al. 2008). ...
Metodika monitoringu chloroetenů ve vybraných složkách životního prostředí, včetně biologických matric, postupy pro hodnocení difuzního znečištění ve stromech, rybách a vodních tocích. Metody pro hodnocení rizik pro člověka a ekosystémy.
... Fish are the main taxa studied with regard to MP ingestion in freshwater environments 40 and constitute an economically, ecologically, and highly diversified group. 41,42 Microplastic ingestion by freshwater fish has been studied worldwide, but these studies have focused on limited regions ( Figure 1) in comparison with the studies of plastic ingested by wild marine fish. 43 In total, the studies focusing on freshwater fish, while few, have described MP ingestion by more than 200 species. ...
Plastic pollution, especially microplastics (MP) pollution, is a hot topic in both mainstream media and scientific literature. Although rivers are potentially the major transport pathway of this pollution to the sea, plastic contamination in freshwater bodies is comparatively understudied. Microplastic pollution in freshwater fish is of growing interest, and while few studies exist, discrepancies do occur in the sampling, extraction, and identification of MP and in the expression of the results. Even though those differences hamper comparisons between some studies, a comparative work has been performed to identify the factors influencing MP ingestion by fish and consequently to target potential ecological traits that can be used to monitor species. Monitoring plastic ingested by fish will give relevant ecological information on MP pollution. This review focuses on MP ingestion by wild freshwater and estuarine fish. In addition to providing an overview of the existing data concerning contamination levels in wild freshwater fish, we aimed to (1) propose several overall recommendations on the methodologies applicable to all biota, (2) compare MP contamination levels in fish and in their environment, and (3) determine which parameters could help to define fish species for monitoring.
... The knowledge of biomarker responses is very useful in risk evaluation of the presence of hazardous substances or mixtures of chemicals in the marine environment (Aarab et al., 2004;Moore et al., 2004;Broeg and Lehtonen, 2006;Dagnino et al., 2007;Damiens et al., 2007;Tejeda-Vera et al., 2007;Viarengo et al., 2007;Wang et al., 2010;Piva et al., 2011;Marigómez et al., 2013;Hylland et al., 2017;Vethaak et al., 2017). Fish species play a fundamental ecological role as carriers in the marine food chain from the lower to higher trophic level, through which the pollutants can be absorbed (Powers, 1989). In this regard, the evaluation of possible exposure in fieldcollected organisms through biomonitoring of the effects on wild populations, can be more ecologically meaningful than laboratory tests (Connon et al., 2012). ...
Pesticides are one of the most frequently anthropogenic xenobiotics detected in water. Among these, the organophosphorus pesticides (OPs) are very widely used in agriculture due to their broad spectrum of activity and their low price, but they also have high potent effects as neurotoxic compounds in non-target organisms. The aim of this study was to evaluate biomarkers acetylcholinesterase (AChE), butyrylcholinesterase (BChE), propionylcholinesterase (PChE) and carboxylesterase (CbE) in the representative Atlantic fish species Trachurus trachurus, Merluccius merluccius and Trisopterus luscus from “Rías Gallegas”, a traditional Spanish fishing area. These esterase activities were evaluated in the brain, muscle and liver to determine the most adequate tissue to measure such enzymatic activities. The sensitivity of AChE and CbE activities from different tissues the widely used organophosphorus insecticide chlorpyrifos (CP), and its toxic metabolite (CP-oxon) was also tested. AChE activity was predominant in all tissues of the analysed species (particularly in brain constituting from 78.33%, 89.83% and 88.43% of total ChEs in Trachurus trachurus, Merluccius merluccius and Trisopterus luscus, respectively). Under in vitro exposure, esterases were shown to be highly sensitive to CP and especially to CP-oxon. Moreover, a similar effect observed on AChE and CbE activities could suggest that CbE activity might contribute efficiently against the toxic effects of CP, especially in muscle and the liver. The presence of BChE, PChE and upper CbE activities in muscle and the liver and their OP-sensibilities can be used to study their function in the pesticide biochemical detoxification pathways with a prominent role as a safeguarding mechanism against pesticide toxicity.
... Fish are widely used as sentinels for aquatic ecosystem pollution stemming from chemical exposure and are the preferred model for development of chemical testing guidelines (10,11). Among others, their practical relevance are based on: (i) wide distribution in aquatic environments; (ii) high ecological relevance due to position within food web structure, nutrient cycling and energy transfer; and (iii) expanding models and tools that researchers can use (12). ...
In recent years, the unique properties of nanoparticles have fostered novel applications in various fields such as biology, pharmaceuticals, agriculture, and others. Unfortunately, their rapid integration into daily life has also led to environmental concerns due to uncontrolled release of nanoparticles into the aquatic environment. Despite increasing awareness of nanoparticle bioaccumulation in the aquatic environment, much remains to be learned about their impact on aquatic organisms and how to best monitor these effects. Herein, we provide the first review of innate immunity as an emerging tool to assess the health of fish following nanoparticle exposure. Fish are widely used as sentinels for aquatic ecosystem pollution and innate immune parameters offer sensitive and reliable tools that can be harnessed for evaluation of contamination events. The most frequent biomarkers highlighted in literature to date include, but are not limited to, parameters associated with leukocyte dynamics, oxidative stress, and cytokine production. Taken together, innate immunity offers finite and sensitive biomarkers for assessment of the impact of nanoparticles on fish health.
... Fish evolved around 500 million years ago and currently they form the oldest and most diverse vertebrate group which includes more species than all other vertebrate groups combined (Xiaobo et al., 2010). The evolutionary position of fish and their ability to adapt to diverse environmental conditions made them frequently used as models for every biological discipline including neurobiology, physiology, toxicology, endocrinology, developmental biology and environmental research (Powers, 1989). ...
ABSTRACT
The present study included two parts which focus on:
1- Theeffect of taurine onantioxidant parameters and some respiratory parameters in Sea bass (Dicentrarchus labrax) under conditions of forced swimming uses.
2- The relaxant effect of taurine on intestinal segments and aortic rings in the common carp(Cyprinus carpio), with a specialemphasis on the rate of ion channels and endothelial derived hyperpolarizing factors.
1. Effect of Taurine on Biometric and Respiratory Parameters in Sea bass
This part of thework aimed to studythe effect of taurine on biometric parameters, some respiratory parameters,swimming performances, respiratory burst and molecular analysis(mRNA gene expression)in adult Sea bass, from bothsexes, weighting (75-110g). The fishes were used in this partcollected from Nouva Azzurro commercial hatchery (Civitavecchia, Roma, Italy), and transported to the animal house and stocked into indoor tanks 2500L capacity. The fishes were allowed to acclimate to the laboratories conditions for 90 days before starting the experiments. The tanks were connected to a sea water recirculation system. After acclimation of the fish, they were subdivided into two subgroups and each of which was further subdivided into two dependent groups (34 and 64 days) for feeding and swimming performances (AutoTMResp, Loligo® Systems, Tjele, Denmark). The fish of the first group were fed on commercial pellets,whereas, in the second group, they were fed on commercial pellets plus 1.5% taurine. The time period of feeding and swimming performance in first set of this experiment was thirty four days whereas in the second set, it was sixty four days.
The respiratory burst (RB) was measured four times. The first measurement (T0)was donebefore separating the fish. The second measurement (T1)was done after fifteen daysof feeding infirst set of experiment and thirty days in the second set of the experiments. The third measurement (T2)was done after four days of resting the fish. The last measurement (T3)was done after 15 days of feeding in the 1st part of experiments and 30 days after the 2nd part of feeding.
The biometric performances results revealed thatfish fedon commercial pellets plus 1.5% taurine for 15 days did not show any significant changes in body weight. Whereas after 34 days of feeding the fishes fed oncommercial pellets plus 1.5% taurine, there was a significant elevation in the BW as compared with that of control groups before and after training the fish in swimming chamber respirometer. Furthermore, the effect of taurine on total body length did not show any significant changes in all of feeding periods T0, T1, T2 and T3.The level of condition factor was significantly increased in fish's fedcommercial pellets plus 1.5% taurine after exercising in swimming chamber T1 and T3 for 15 days and 34 days, respectively.Fish were fed oncommercial pelletsplus 1.5% taurine for 15 days did not show any changes in specific growth rate, whereas, there was a significant elevation in the growth rate in fish fed oncommercial pellets plus 1.5% taurine.The feed conversion ratio did not changed significantly after feeding the fishon commercial pellets plus 1.5% taurine for 15 days whereas, after 34 days of feeding there wasa significant increase in FCR.
After exercising the fish in the respirometerswimming chamber, the critical swimming speeds (Ucrit-1) and (Ucrit-2) showed significant elevation in fish fedon commercial pellets plus1.5% taurine after exercising in swimming chamber for 15 days but after 30 days (Ucrit-1) did not show any change whereas (Ucrit-2) showed significant elevation in fish fed oncommercial pellets plus 1.5% taurine.The rate of oxygen consumption (mg O₂kg-1hr-1) showed nochanges after feeding the fishwith pellets plus 1.5% taurine.The level of standard metabolic rate (SMR), routine metabolic rate (RMR) and active metabolic rate (AMR) were significantly decreased when fishwerefed oncommercial pellets plus1.5% taurine.Antioxidant effect of taurine did not change the energy required for fish to move (Cost of transport) and aerobic scope(mg O₂kg-1hr-1) after exercising in respirometer swimming chamber.
The results of respiratory burst revealed a significant inhibition in the level of integral relative light unit (IRLU) before and after exercising the fish in swimming chamber respirometer during times T1, T2 and T3 in fish fed oncommercial pellets plus 1.5% taurine as compared with the control group. After exercising,five fish from each group were taken out from the water and sacrificed by immersion in crushedice. The tissue samples were taken at the time of death by taking out sections from red muscle and the liver tissues.
The total RNA was extracted from the red muscle and liver tissues by using the Maxwell® 16 LEV simply RNA Tissue Kit (Promega, Italy). The absolute number of catalase (CAT), superoxide dismutase (SOD) and glutathione proxidase (GPX) gene transcript copies could bequantified by comparing them with a standard graph constructedusing the known copy number ofmRNA of this gene
The levels of CAT mRNA gene expression in liver and red muscle did not show any significant changesin fish fed oncommercial pellets plus 1.5% taurine in both feeding times of 34 days and 64 days. Similarly, fish fed on diet plus 1.5% taurine did not show any significant change in the level of liver SOD and GPX mRNA gene expression when comparedwith fish fed oncommercial pellets during both time periods 34days and 64 days. On the other hand, the levels of red muscle SOD and GPXin fishes fed oncontrol diet plus 1.5% taurine for 34 days showed a significant elevation in mRNA copy number/100ng RNA. However,the level of red muscle SOD and GPX showed nosignificant change in fishes fed oncontrol diet plus 1.5% taurine.
2.The Relaxant Effect of Taurine
The second part of the current work included the relaxant effects of taurineon isolated intestinal segments and aortic rings of common carp.PowerLab Data Acquisition Organ Bath System (ADI) was used to measure the isometric tension resulted from smooth muscle contractility. Prior to the experiment, the organ bath was set at 20oC forat least one hour, followed by the addition of 5ml Ringer’s solution to the glass tissue chamber containing intestinal segments and 10ml to the chamber containing aortic rings. The preparation was aerated continuously with 99.7%oxygen (O2) and 0.3 % carbon dioxide (CO2). The resting tensions for intestinal segments was calibrated at0.5gram, whereas,for aortic rings were calibrated at 2gram.
This part of the work aimed to study the relaxant effect of taurine on intestinal and aortic smooth muscle and role of potassium (K+) and L- type Ca++ channels in taurine induced relaxation. In addition, it also included the role of endothelium derived hyperpolarizing factors such as L-nitro arginine methyl ester (L-NAME) (NO synthase inhibitor), Indomethacin, (cyclogenase inhibitor) and methylene Blue (cGMP inhibitor) on taurine induced relaxation in the studied tissues. Taurine produced enhanced relaxant responses in intestinal segments as compared to aortic rings. The results also indicated the presence on intra-specific variation in the role of various K+ channel subtypes in taurine induced relaxation. Thus, using different K channel subtype blockers revealed that in intestinal segments, both KATP and Kca channel subtypes played significant roles in taurine induced relaxation, while KV and KIR played no role. On the other hand, in aortic rings, both KIR and Kca, but not KATP and KV, played significant roles in induced vasorelaxation. The results also indicated that Nifedipine (L- type Ca++ channels blocker), significantly diminished the relaxation induced by taurine in aortic rings. This reflect the important role of L-type Ca++ channel in taurine induced relaxation, while a similar effect was not exhibited by intestinal L-type Ca++ channels since, Nifedipine enhanced the taurine induced relaxation instead of its inhibition.
Furthermore, experimental results also indicated that endothelial derived hyperpolarizing factors such as, NO, cyclogenase and cGMP have no effects on taurine induced relaxation in intestinal and aortic tissues; except at the highest taurine concentration used (2x10-2M) which significantly reduced the induced relaxation in aortic rings. From the results of the current study it can be concluded that taurine induced relaxation in intestinal smooth muscle involves the activation of KATPand Kca channel; whereas, aortic smooth muscle, involves the activation of KIR, Kca, and Ca++ Channels with a partial participation of NO.
... According to DE LA TORRE et al. (2005) monitoring sentinel fish species is widely used to assess the degree of accumulation of pollutants and the effects on health status. In addition, fish have been found to be good indicators of water contamination in aquatic systems because they occupy different trophic levels; they are of different sizes and ages and in comparison with invertebrates, are also more sensitive to many toxicants (DALLINGER et al., 1987;POWERS, 1989;BARAK & MASON, 1990;WESTER et al., 1991;BURGER et al., 2002) Fish respond to environmental toxic changes with adapting of their metabolite functions (MISHRA & SHUKLA, 2003). They are also preferred in toxicological research because of their well-developed osmoregulatory, endocrine, nervous, and immune systems compared to invertebrates (SONG et al., 2012). ...
EU Member states are required to apply the EU Water Framework and its Daughter Directives in order to achieve Good Environmental Status (GES) for all 11 qualitative descriptors by 2015 in all water bodies for a list of priority and specific pollutants. Therefore, environmental indicators and biological-effect techniques have to be carefully selected for the management of chemicals in the aquatic environment and for developing an integrated framework. The most commonly applied biological-effect tools are measures of the biochemical and physiological state of selected organisms, such as mussels or fish. The present article provides basic information on the EU Water Directive, the essence of biomarkers, and outlines why mussels may be the better choice of indicators in toxicological research and monitoring programs in order to study the impact of contaminants in water ecosystems.
... Fish are a major test organism in ecotoxicological studies because of their link to man in the food chain [17] . Also, they are particularly useful for the assessment of waterborne and sediment-deposited toxins where they may provide advanced warning of the potential danger of new chemicals and the possibility of environmental pollution [21] . Clarias gariepinus are found throughout the world, especially in Africa and the Middle East (Froese and Pauly, 2014) [10] and live in fresh water lakes, rivers and swamps, as well as human made habitats such as oxidation ponds. ...
The acute toxicity of formaldehyde on African catfish (Clarias gariepinus) fingerlings was studied using the static bioassay. The fishes were fed twice daily at 2.5% of their body weight for 21 days. The rate of fingerlings mortality increased with increasing concentration of formaldehyde. The first death was noticed two minutes after the introduction of toxicant in the bowl with the lowest concentration in (30.0 mg/L), other behavioural symptoms include restlessness, rapid body movement, and difficulty in respiration displayed by fishes moving to the surface to gulp air, intense opercula movement, accumulation of mucus on body and loss of equilibrium by swimming sideways. A log concentration probit regression analysis was significant (p<0.05) and yield a coefficient of determination, r 2 = 0.637. The LC50 and 95% confidence limits to the concentration of formaldehyde was determined as 1.80 ± 0.25 ppm and LC50 interval of 0.706-2.094 ppm. The results showed the necessity to regulate the discharge of formaldehyde from domestic and industrial sources into aquatic systems, hence the need for caution on it uses even in fish harvesting.
... This thesis is based on data presented in the following articles, referred to by the Roman Numerals I-IV. Powers, 1989;Axelsson et al., 1992;Johnston et al., 1994). With the exception of some 30 partially endothermic species (Dickson and Graham, 2004), all fish are ectotherms, i.e. their body temperature is dependent on and in equilibrium with the ambient water temperature. ...
... Fish are a useful vertebrate model for biomedical research (for screening drug safety, elucidating mechanisms of human diseases and assessing environmental health) due to relatively short duration of embryonic development (Powers 1989;Rocha et al. 2017). Toxicity (especially embryotoxicity) of QDs is still poorly investigated, and the results vary (King-Heiden et al. 2009;Zhang et al. 2012;Zolotarev et al. 2012;Rocha et al. 2017). ...
Due to the active development and application of nanotechnology, nanoparticles have emerged as a new class of environmental pollutants. The aim of the study was to investigate quantum dots (QDs) access routes and distribution in embryos and larvae of rainbow trout Oncorhynchus mykiss and to determine the toxicity of QDs to rainbow trout larvae depending on the duration of exposure. CdSe/ZnS–COOH QDs at sublethal concentration was used during the toxicity test (1, 4 and 14 days). The results showed that QDs could get from the solutions into the larvae after hatching. QDs induced a significant increase in mortality, gill ventilation frequency and behavioral responses and a decrease in relative body mass in larvae at the end of the test. Larvae exposed to QDs were found to possess developmental malformations (blood clots). It was found that biological responses of larvae significantly depended on the duration of exposure to QDs.
... In parallel with efforts to understand ecological consequences of pharmaceuticals in urban systems, a marked increase in the use of fish models for biomedical research has occurred, including studies of chemical carcinogenicity and other toxicology questions (Fig. 1) (Hinton et al., 2009). Fish models are employed during early phases of drug development and safety evaluations due to animal welfare concerns, rapid rates of reproduction, and lower costs of care, husbandry and testing (Powers, 1989). For example, zebrafish are increasingly used in neuropharmacology, where behavioural phenotypes associated with various moods, psychological disorders and social preferences have been reported following exposure to neuroactive chemicals, including pharmaceuticals and pesticides (Stewart et al., 2015;Kalueff et al., 2016). ...
Pharmaceuticals are routinely reported in the environment, which indicates an increasingly urban water cycle and highlights a global megatrend. Physicochemical properties and intrinsic biological activity of medicines routinely differ from conventional organic contaminants; thus, diverging applicability domains often challenge environmental chemistry and toxicology computational tools and biological assays originally developed to address historical chemical stressors. Because pharmacology and toxicology information is more readily available for these contaminants of emerging concern than other chemicals in the environment, and many drug targets are conserved across species, leveraging mammalian drug discovery, safety testing and clinical pharmacology information appears useful to define environmental risks and to design less hazardous industrial chemicals. Research is needed to advance biological read across, which promises to reduce uncertainties during chemical assessment aimed at protecting public health and the environment. Whereas such comparative information has been critical to advance an understanding of pharmaceutical hazards and risks in urban ecosystems, studies of medicines with fish and other ecotoxicological models are reciprocally benefiting basic and translational efforts, advancing comparative mechanistic toxicology, and providing robust comparative bridges for integrating conservation and toxicology.
With the expansion of human settlements and the environmental changes brought about by human activity and pollutants, toxicology and risk assessment of amphibian species has become increasingly of interest to toxicologists involved in environmental research.
This book focuses specifically on environmental risk assessment in premetamorphic stages and adults of amphibians. Amphibian ecotoxicology is not totally understood in scientific research and as such environmental risk assessment in these vertebrates is an area of rapidly growing interest. It has the potential to answer some of the questions regarding risks to our environment.
An ideal companion, this book will be useful to toxicologists and ecologists investigating risk assessment in the environments of amphibians, while also of interest to those working in conservation biology, biological invasion, biocontrol and habitat management.
Haematopoietic necrosis in Carassius auratus is one of the most serious diseases in recent years caused by CyHV-2 (cyprinid herpesvirus 2) which has caused huge economic losses in aquaculture. Currently, the isolation and propagation of CyHV-2 in vitro is difficult due to the lack of sensitive cell lines, which hinder further studies on the pathogenesis and gene functions of the virus. In this study, Carassius carassius gill cell line (CCG) was constructed and had been passaged up to 90 passages at 25 ℃ in Medium199 (M199) with 15–20% Foetal bovine serum (FBS). Cellular karyotype analysis showed that the chromosome number was 46 at passage 50. CCG could be successfully transfected with GFP reporter gene with an efficiency of more than 60% suggesting that CCG could be used for exogenous gene expression in vitro. CCG infected with CyHV-2 displayed typical cytopathic effects (CPE), and viral replication was confirmed by PCR, indirect immunofluorescence assay (IFA) and transmission electron microscopy (TEM) assay, respectively. In conclusion, the CCG cell line can be used as a useful tool to study the propagation and pathogenesis of CyHV-2.
A new continuous fish cell line (CAM) has been successfully derived from the muscle tissues of grass goldfish, Carassius auratus. The primary cell cultures were initiated by incomplete trypsinization first and then explant culture in a Leibovitz-15 medium supplemented with 15% fetal bovine serum and 10% fish muscle extract. It was found that the CAM cells were very sensitive to trypsinization and needed to be sub-cultured at a low trypsin concentration of 0.0625% to be able to go through the crisis of spontaneous immortalization transformation, and afterward a total of five derivative cell strains were isolated from the original CAM cell line. This spontaneous immortalization transformation event was recorded successively at passages 44–47, beginning with a large-scale apoptosis and senescence and followed by mitosis arrest and re-activation, thus designated as cell strain CAM-44A, 44B, 45A, 44B, and 47A. Now both the CAM cell line and strains had been sub-cultured for more than 89 times and could be well cryopreserved in the growth medium containing 5% dimethylsulfoxide. Chromosome analysis and COI gene analysis had confirmed the grass goldfish origin of these CAM cells. Transfection potential analysis indicated that Lipofectamine LTX and Xfect were two suitable transfection reagents to be used in the gene delivery of CAM cells with a transfection efficiencies up to 11±6% and 8±3% in the CAM cell lines, respectively. Among the five cell strains, CAM-47A showed the highest transfection potential with a transfection efficiency up to 28 ± 5%. This work will provide a useful cell source for works on the cell-based artificial fish meat production and functional studies of fish myogenesis-related genes.
Anthropogenic pollution represents a significant source of selection, potentially leading to the emergence of evolutionary adaptations in chronically exposed organisms. A recent example of this scenario corresponds to Gulf killifish (Fundulus grandis) populations inhabiting the Houston Ship Channel (HSC), Texas, USA, which have been documented to have adapted to this heavily contaminated environment. Although not fully elucidated, one particularly important aspect of their adaptation involves the reduced inducibility of the aryl hydrocarbon receptor (AhR) and, potentially, the alteration of major biotransformation pathways. In the present study, we employed a modified Organization for Economic Cooperation and Development (OECD) 319-B test guideline to explore population and sex-related differences in the hepatic biotransformation of six polycyclic aromatic hydrocarbons (PAHs) in F. grandis populations with different exposure histories. Pollution-adapted F. grandis showed significantly lower hepatic clearance of PAHs than non-adapted fish, especially for high molecular weight PAHs (chrysene, benzo[k]fluoranthene, and benzo[a]pyrene), with pollution-adapted females presenting the lowest clearance. The characterization of different phase I biotransformation enzymes revealed that the basal activity of CYP1A, fundamental in the biotransformation of PAHs, was significantly lower in pollution-adapted fish, especially in females, which showed the lowest activity. Contrarily, basal CYP2C9-like activity was significantly higher in pollution-adapted fish. These results demonstrate the importance of exposure and evolutionary histories in shaping organisms' responses to pollution and provide significant evidence of sex-specific biotransformation differences in F. grandis populations.
Freshwater and marine water bodies receive chemical contaminants from industrial, agricultural, urban, and domestic wastes. Eco-genotoxicity assays are useful tools to assess the cumulative genotoxicity of these pollutants. Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution.
In this review, we present a complete overview of the studies performed so far using the micronucleus test in peripheral erythrocytes of fish exposed to polluted water. We have listed all the species of fish used and the geographical distribution of the investigations. We have analyzed and discussed all technical aspects of using this test in fish, as well as the advantages and disadvantages of the different experimental protocols. We have reported the results of all studies. This assay has become, for years, one of the simplest, fastest, and most cost-effective for assessing genotoxic risk in aquatic environments. However, there are still several factors influencing the variability of the results. Therefore, we have given indications and suggestions to achieve a standardization of experimental procedures and ensure uniformity of future investigations.
Marine ecosystems in general, and coastal ecosystems in particular, suffer significant, diverse and, unfortunately, increasing, destructive impacts due to anthropogenic activities, including habitat devastation, biodiversity losses, and chemical contamination, resulting in severe ecological and human health effects. Elasmobranchs, comprising sharks and batoids (stingrays, skates, guitarfishes and sawfishes), in particular, play a key role in marine trophic network interactions, and threats to this group may lead to severe ecosystem imbalances. This group suffers several pressures, such as the finning market, meat consumption in developing countries, the sale of elasmobranch-derived products, climate change and chemical contamination, among others. Specifically concerning chemical contamination, several elasmobranch species occupy intermediate to high trophic levels, therefore becoming highly exposed to environmental contamination through the dietary route or through sediment association. This may result in both ecological effects, as several contaminants can affect elasmobranch physiology, resulting in decreased recruitment rates, reproductive failures and maternal contaminant transfer, and human health issues through elasmobranch meat consumption. Yet, interestingly, contamination assessments concerning this group and its implications, both ecological and human, are still scarce worldwide, albeit increasing in recent years. Taking this scenario into account, this chapter will discuss an integrated ecotoxicological view on elasmobranch conservation regarding chemical contamination, alongside potential ecological outcomes for this group and human impacts derived from elasmobranch consumption.
Sex steroids, produced by the gonads, play an essential role in brain and pituitary tissue plasticity and in the neuroendocrine control of reproduction in all vertebrates by providing feedback to the brain and pituitary. Teleost fishes possess a higher degree of tissue plasticity and variation in reproductive strategies compared to mammals and appear to be useful models to investigate the role of sex steroids and the mechanisms by which they act. The removal of the main source of sex steroid production using gonadectomy together with blood sampling to measure steroid levels has been well-established and fairly feasible in bigger fish and is a powerful technique to investigate the role and effects of sex steroids. However, these techniques raise challenges when implemented in small size teleost models. Here, we describe the step-by-step procedures of gonadectomy in both males and female Japanese medaka followed by blood sampling. These protocols are shown to be highly feasible in medaka indicated by a high survival rate, safety for the life span and phenotype of the fish, and reproducibility in terms of sex steroid clearance. The use of these procedures combined with the other advantages of using this small teleost model will greatly improve the understanding of feedback mechanisms in the neuroendocrine control of reproduction and tissue plasticity provided by sex steroids in vertebrates.
The master sex determinant in rainbow trout (Oncorhynchus mykiss), sexually dimorphic on the Y chromosome (sdY), is strongly but not perfectly associated with male phenotype in several other species from the family Salmonidae. Currently, the cause and implications of discordance for sdY-predicted genotypic sex and phenotypic sex in these species is unclear. Using an established multiplex PCR test for exons 2 and 3 of sdY, we demonstrated that sdY-predicted genotypic sex was discordant with histologically evidenced phenotypic sex in 4% of 176 Tasmanian Atlantic salmon. All discordant individuals were phenotypic females presenting a male genotype. Using real-time qPCR assays that we developed and validated for exons 2, 3 and 4 of sdY, all genotype-phenotype discordant females were confirmed to possess sdY, albeit at a reduced number of copies when compared to phenotypic males. The real-time qPCR assays also demonstrated reduced levels of sdY in 30% of phenotypic females that the established multiplex PCR-based test indicated to be devoid of sdY. These findings suggest sdY may be reduced in copy number or mosaicked in the genomic DNA of sdY-positive phenotypic female Atlantic salmon and highlight the importance of understanding the effects of reduced sdY copies on the development of phenotypic sex.
We present here results from model experiments with poikilotherm hydrobionts belonging to different taxonomic groups: crayfish (Pontatacus leptodactylus), fish, i.e., carp (Cyprinus carpio), and amphibians, i.e., axolotl (Ambystoma mexicanum). Fatty dystrophy of the hepatopancreas in crayfish and pathology of the pancreas in carp were modeled by administration of alloxan at doses of 50 and 200 mg/kg, respectively. Crayfish received alloxan into the ventral sinus and fish were treated i.p. Liver pathology in fish was modeled by administration of seven doses of paracetamol 15 g/kg over 14 days. Parenteral administration (into the central sinus of crayfish, i.v. in fish, and i.p. in axolotls) of stem and progenitor cells from mammalian donors (mice) at a dose of 10·10⁶ bone marrow cells (BMC) was found to have effects. Fish and crayfish with pathology displayed intensive tissue regeneration and restoration of damaged parenchymatous organs. Administration of stem cells accelerated the process of regeneration of amputated limbs in axolotls. These results extend the potential of medical-biological studies of in vivo models.
Freshwater ecosystems are among the most threatened environments on our planet. Disturbances across the terrestrial landscape accrue within freshwater ecosystems and, combined with global stressors like climate change and invasive species, create a complex situation for recovering imperilled fishes. Given the drastic global trend of freshwater fish declines, similarly extreme efforts are needed for their conservation and recovery – repatriation represents one such opportunity. Species repatriation describes the act of releasing a species in areas where extirpation has occurred. Paradoxically, a long history of fish introductions for recreational purposes exists, yet examples of repatriation for imperilled fishes are relatively rare compared to terrestrial species. Stemming from the restoration and species introduction literature, we identify five ecological themes to consider when evaluating repatriation potential of freshwater fishes and suggest that repatriation represents the “drastic” approach needed to achieve meaningful conservation milestones.
In order to evaluate whether structural differences exist between allelic variants of a B-type lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) in the minnow Fundulus heteroclitus, the allozymes (LDH-Ba4, LDH-Ba/Bb, and LDH-Bb4) were purified to homogeneity by affinity chromatography. Each variant was characterized as to holoenzyme and subunit molecular mass, isoelectric point (pI), thermal and urea stability, and susceptibility to proteolysis. Differences in electrophoretic mobilities were due to a lower pI for LDH-Ba4 (pI = 6.6) than for LDH-Bb4 (pI = 7.2). Stability to inactivation by heat, urea, and proteolysis was in each case: LDH-Bb4 greater than LDH-Ba/Bb greater than LDH-Ba4. Inactivation by trypsin may involve the arginine-rich catalytic loop of lactate dehydrogenase (50). The results suggest that the allozymes differ in their conformational flexibility.
The nicotinic acetylcholine receptor (AChR) from fish electric organ and mammalian skeletal muscle is the best characterized neurotransmitter receptor (reviewed in refs 1–3). The AChR from the electroplax of the ray Torpedo californica consists of five subunits present in a molar stoichiometry of α
2
βγδ (refs 4–6); the apparent molecular weights of the α-, β-, γ- and δ-subunits are 40,000 (40K), 50K, 60K and 65K, respectively7–11. Knowledge of the primary structures of these constituent polypeptides would facilitate the understanding of the molecular mechanism underlying the function of the neurotransmitter receptor. Recently, we have cloned cDNA for the α-subunit precursor of the T. californica AChR and have deduced the primary structure of this polypeptide from the nucleotide sequence of the cloned cDNA12. Here we report the cloning and nucleotide analysis of cDNAs for the AChR β- and δ-subunit precursors. The primary structures of the two polypeptides deduced from the cDNA sequences reveal conspicuous amino acid sequence homology among these and the α-subunits. The three subunits contain several highly conserved regions which may be essential for the receptor function or inter-summit interaction.
The sodium channel is a voltage-gated ionic channel essential for the generation of action potentials. It has been reported that the sodium channels purified from the electric organ of Electrophorus electricus (electric eel) and from chick cardiac muscle consist of a single polypeptide of relative molecular mass (Mr) approximately 260,000 (260K), whereas those purified from rat brain and skeletal muscle contain, in addition to the large polypeptide, two or three smaller polypeptides of Mr 37-45K. Recently, we have elucidated the primary structure of the Electrophorus sodium channel by cloning and sequencing the DNA complementary to its messenger RNA. Despite the apparent homogeneity of the purified sodium channel preparations, several types of tetrodotoxin (or saxitoxin) binding sites or sodium currents have been observed in many excitable membranes. The occurrence of distinguishable populations of sodium channels may be attributable to different states of the same channel protein or to distinct channel proteins. We have now isolated complementary DNA clones derived from two distinct rat brain mRNAs encoding sodium channel large polypeptides and present here the complete amino-acid sequences of the two polypeptides (designated sodium channels I and II), as deduced from the cDNA sequences. A partial DNA sequence complementary to a third homologous mRNA from rat brain has also been cloned.
In order to evaluate whether functional differences exist between allelic variants of a B type lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) in the teleost fish Fundulus heteroclitus (Linnaeus), the kinetic properties of pyruvate reduction were examined. While the pH dependence and the temperature dependence for maximal catalysis were indistinguishable among the allozymes, reaction velocities at low pyruvate concentrations were significantly different. At pH values below 8.00, the LDH-BbBb allozyme showed a greater reaction rate at lower temperatures (e.g., 10 degrees C) than LDH-BaBa. The phenomenon was reversed at higher temperatures (e.g., greater than 25 degrees C) for pH values between 6.50 and 7.00. The rates for the heterozygous phenotype, LDH-BaBb, were not the arithmetic average of the two homotetrameric allozymes. When reaction rates were compared at constant relative alkalinity, that is, a constant [OH-]/[H+] ratio, the findings were similar. The differences in the temperature dependence and the pH dependence for pyruvate reduction found between the LDH-B allozymes may reflect a selective adaptation and help explain the geographical variation in the Ldh-B gene frequencies of F. heteroclitus.
The tetrodotoxin-binding component associated with the voltage-sensitive sodium channel from electroplax membranes of Electrophorus electricus has been purified. The toxin-binding site could be efficiently solubilized with Lubrol-PX, resulting in an extract of high initial specific activity. Purification was facilitated by the development of a rapid, quantitative binding assay. The binding component was stabilized during purification by the use of mixed lipid/detergent micelles of defined composition, and by the saturation of the site with tetrodotoxin. The purification was achieved by means of a highly selective adsorption of the toxin-binding component to DEASE-Sephadex A-25, followed by desorption at high ionic strength and chromatography over Sepharose 6B. Final peak specific activities were at least 50% of the specific activity expected for a pure, undenatured toxin-binding componenet of 230,000 molecular weight. The purified material exhibited a sedimentation coefficient of approximately 8 S and an unusual Stokes radius of 95 A. Purified material showed a relatively simple pattern on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, being comprised of only three polypeptides.
Purified Tilapia growth hormone (GH), which has already been shown to have slight but significant activity in the rat tibia assay, was found to promote growth in two intact teleost species, Tilapia mossambica and Oncorhynchus nerka (sockeye salmon). Tilapia GH and bovine GH were approximately equipotent in stimulating an increase in both length and weight of these fish. In salmon, ovine prolactin (PRL) stimulated growth with a much lower potency than Tilapia GH, while Tilapia PRL was inactive. Furthermore, bovine GH, Tilapia GH, and ovine PRL facilitated adaptation of the salmon to sea water, while Tilapia PRL had no effect. These data, along with published results of teleost bioassays specific for Tilapia PRL, demonstrate that teleosts can readily distinguish between Tilapia GH and Tilapia PRL. This separation contrasts with previously reported similarities between the two hormones with respect to amino acid composition, immunochemistry, and activity in the rat tibia assay.
Geographic variation in the gene frequencies corresponding to 15 polymorphic enzymes were studied in the common killifish Fundulus heteroclitus. Aat-A, Est-B, Fum-A, H6pdh-A, Mpi-A and Pgm-B showed clinal variation in allelic frequencies along the Atlantic coast of North America, while Aat-B, Ap-A, and the EST-C phenotypes did not. The clinal allelic variation of six previously examined loci (Ldh-B, Mdh-A, Gpi-B, Idh-A, Pgm-A, and 6-Pgdh-A) was extended to locations farther north. Gene diversity was lowest in the cold waters of northern latitudes and highest in the warmer waters of southern latitudes. The variety of clinal shapes and widths suggests that selection has affected the allelic distributions for at least some of these loci. This hypothesis is discussed with regard to the range contractions and extensions caused by the glacial advances and retreats during the Pleistocene.
The fishes, like all the other vertebrates, reproduce sexually. This chapter describes embryology, as well as morphology that is essential to understand the features of the comparative physiology of the reproductive system of fishes. In majority of species, eggs and spermatozoa are formed in separate individuals and the gametes are expelled into the surrounding water where fertilization takes place and is followed by the development of a new generation. The modes of reproduction are unusual and most of the 20,000 or more known species of fish have male and female organs in separate individuals. Sexual activities are normally followed by the prompt fertilization of eggs, but sometimes sperms are stored in the female for prolonged periods prior to fertilization. Sometimes development occurs, but hatching is delayed during adverse environmental condition. Many specializations associated with reproduction in fishes are discussed in this chapter.
This chapter describes the ion transport and gill ATPases in the fish gills. The gill epithelium is located between two liquid compartments of very different ionic composition. The gills are not only the site of entry for selected ions essential to life but also for the extrusion of other ions, such as HCO3-, NH3+ , and H+, which are the ionic forms of metabolic by-products. The magnitude of unidirectional fluxes, as well as the degree and direction of net fluxes, is dependent on the equilibrium established between the fish and its environment. Membranes are gently treated with ionic detergents, such as deoxycholate, dodecyl sulfate, or chaotropic agents, to release proteic constituents that are less strongly associated with phospholipids, (Na+, K+)-ATPase remaining in situ. Euryhaline species are an attractive model to compare branchial physiology from the adaptation medium and to relate physiological and biochemical aspects of ionic transport. The Ca2+-ATPase is also a membrane ATPase whose role in the cell is essential and evident, but it could also play a role in transepithelial transport and be implicated in the regulation of plasma Ca2+ concentration.
Recently, we reported that genetic variation at the lactate dehydrogenase-B (LDHB) locus of Fundulus heteroclitus is highly correlated with hatching time. In the present study, we explore several mechanisms which may be responsible for this correlation. Since hypoxia-induced hatching occurs when oxygen diffusion limits the metabolic rate of embryos, we tested the hypothesis that LDH-B genotype specific hatching times are the result of metabolic rate differences. While the hypothesis was correct, each genotype appears to receive the hypoxic hatching cue at the same time because the genotype with the higher metabolic rate () was able to bind oxygen at lower partial pressures than the genotype. These results suggested that the genotype simply develops faster. This hypothesis was confirmed by testing the hatching competency of eggs when exposed to hypoxic conditions. Since oxygen consumption rate is generally correlated with growth rate in fishes, our results suggest that individuals develop faster because the allelic isozyme or a closely linked locus acts to increase the metabolic rate of the embryo with respect to the genotype.
Low environmental oxygen stimulates hatching in teleosts and amphibians. Our experiments show that hatching does not occur when oxygen is supplied at a rate that meets the respiratory demands of the embryo and, conversely, that hatching does occur when the metabolic rate of the embryo exceeds a limit set by the diffusion of oxygen through the water column. A mathematical model of oxygen diffusion indicates that a gradient exists such that the concentration of oxygen at the respiratory surface is less than that needed to saturate the blood. Hatching is stimulated when the growing respiratory demand of the embryo creates a hypoxic condition in the microenvironment surrounding the egg.
The occurrence of a large and varied fish fauna in the oceans of the polar regions illustrates how successfully fishes have been able to adapt to extremes of environmental stress. The mechanisms of cold adaptation that permit survival at low temperatures fall into two general categories: (1) mechanisms that permit survival per se at near-freezing temperatures and (2) mechanisms that lead to cold-adapted rates of activities in such physiological functions as respiration and growth. In this chapter, a particularly important example of the first class of cold adaptation mechanisms is considered—namely, the means by which fishes avoid freezing under environmental conditions where ice formation in the body fluids would most likely be favored. The analysis of this phenomenon stresses: (1) the nature of low temperature stresses in freshwater and marine habitats and (2) the varied adaptive responses-both behavioral and biochemical-which offer fishes avenues of escape from injury resulting from freezing. The chapter discusses freezing avoidance in freshwater fishes and in marine fishes.
Dye coupling and cell lineages of blastomeres that participate in the formation of the yolk syncytial layer (YSL) in the zebrafish Brachydanio rerio have been examined. The YSL is a multinucleate layer of nonyolky cytoplasm underlying the cellular blastoderm at one pole of the giant yolk cell. It forms at the time of the 10th (sometimes 9th) cleavage by a collapse of a set of blastomeres, termed marginal blastomeres, into the yolk cell. Marginal blastomeres possess cytoplasmic bridges to the yolk cell before the YSL forms, and injections of fluorescein-dextran into the cells revealed that bridges between the yolk cell and blastoderm do not persist after this time. Injections of Lucifer yellow revealed that shortly after the YSL forms the yolk cell and blastoderm are dye coupled, presumably by gap junctions, and that this coupling disappears gradually during early gastrulation. Lineage analyses revealed that not all of the progeny of early marginal blastomeres participate in YSL formation. Although some descendants of marginal blastomeres remained on the margin during successive cleavages, neither “compartment” nor “strict lineage” models are sufficient to explain the origin of the YSL. It is proposed that the position of a cell on the blastoderm margin, and not the cell's lineage, determines YSL cell fate.
Geographic variation in the gene frequencies corresponding to 15 polymorphic enzymes were studied in the common killifish Fundulus heteroclitus. Aat-A, Est-B, Fum-A, H6pdh-A, Mpi-A, and Pgm-B showed clinal variation in allelic frequencies along the Atlantic coast of North America, while Aat-B, Ap-A, and the EST-C phenotypes did not. The clinal allelic variation of six previously examined loci (Ldh-B, Mdh-A, Gpi-B, Idh-A, Pgm-A, and 6-Pgdh-A) was extended to locations farther north. Gene diversity was lowest in the cold waters of northern latitudes and highest in the warmer waters of southern latitudes. The variety of clinal shapes and widths suggests that selection has affected the allelic distributions for at least some of these loci. This hypothesis is discussed with regard to the range contractions and extensions caused by the glacial advances and retreats during the Pleistocene.
Pollen irradiation has recently been widely investigated as a method for differential gene transfer in plants. Using an albino color marker in rainbow trout (Salmo gairdneri), we have investigated whether irradiated sperm might be used in an analogous manner for gene transfer in fish. Our results indicate that paternal chromosome fragments are genetically active in gynogenetic offspring, but that these fragments may be lost during mitotic cell division, producing mosaic fish.
The metallothionein-human growth hormone fusion gene (MThGH), constructed by fusing the mouse metallothionein promoter with the human growth hormone gene, was microinjected into the cytoplasm of one-cell embryos of channel catfish Ictalurus punctatus. The 3-week-old fish that developed were analyzed for integrated copies of the MThGH gene. Two of 10 animals contained MThGH sequences that comigrated with genomic DNA of high molecular weight in southern blots. The MThGH sequences were organized in head-to-tail tandem arrays that are characteristic of foreign genes integrated into recipient cell genomes. These data strongly suggest that the MThGH genes are stably integrated into chromosomal DNA, and that transgenic channel catfish can be generated by cytoplasmic injection of early embryos.
SYNOPSIS. Growth hormone, prolactin and chorionic somatomammotropin (placental lactogen) area family of hormones that are related by function, immunochemistry and structure. Because of the structural similarities between these hormones, it was proposed that the corresponding genes were derived from a common precursor gene by duplication and sequence divergence. Comparisons of the mRNA sequences and chromosomal genes for these hormones from several species provide additional support for the model of their common ancestry and indications of how the precursor genewas formed. The diversification of these three genes has involved changes in codon choices thataffect the overall G-C content of the genes, alterations in the sizes of introns with conservedexon-intron boundaries and concerted evolutionary mechanisms with duplicated growth hormone andhorionic somatomammotropin genes in humans. The precursor gene appears to have evolved by the fourfold duplication of one exon element and the separate insertion of an exon encoding a different protein domain. Finally, there also appears to have been the separate insertion of sequences containing a promoter element and a potential glucocorticoid regulatory element.
Animals faced with environmental perturbations must adapt or face extinction. The respiratory complex, specifically hemoglobins, is perhaps the best system to study such adaptation because it exists at the organism—environment interface. Fish are particularly useful models because they respond directly to such environmental variables as temperature, oxygen, pH, carbon dioxide, and salinity. Our experiments have addressed the molecular, cellular, and physiological mechanisms employed by fish to maintain respiratory homeostasis in the wake of changing temperature and oxygen. Immediate, intermediate, and long-term adaptation can only be understood when the hemoglobin's ligand binding properties and the cellular and hormonal regulation of various ligands are considered simultaneously. We describe a detailed thermodynamic model for the binding of oxygen, protons, and organic phosphates to hemoglobin; discuss the role of multiple hemoglobins; and present evidence for physiological and genetic regulation of hemoglobin's major allosteric modifiers in response to environmental stress in the mummichog, Fundulus heteroclitus
The evolutionary significance of protein polymorphisms has been long debated. Exponents of the balanced theory advocate that selection operates to maintain polymorphisms, while those of the neoclassical school argue that most genetic variation is selectively neutral. In a series of laboratory and field experiments conducted over the last 5 years, we have found that the developmental rates of Fundulus heteroclitus embryos were highly correlated with genetic variation at 3 enzymatic loci: lactate dehydrogenase-B, malate dehydrogenase-A, and glucose phosphate isomerase-B. Pairwise comparisons of these loci generally indicated an averaging of developmental rates; however, a synergysm was found between the MDH-A and GPI-B loci. Our field studies indicated that selective forces may contribute to the maintenance of these polymorphisms via hatching time selection. Since feral eggs incubate aerially during the neap tides, either very rapid or very slow developmental rates may lead to deleterious stranding above the water line. In addition, very slow developmental rates may lead to increased predation pressure.
Studies of 16 polymorphic loci in the fish Fundulus heteroclitus have uncovered significant directional changes in gene frequencies with latitude (i.e., clines). These spatial patterns could have arisen by primary and/or secondary intergradation. While we cannot presently distinguish between these two models, mitochondrial DNA analyses indicate that if previous isolation occurred as required for secondary intergradation, it must have been relatively recent and of short duration. Herein we discuss the roles of genetic drift, random migration, nonrandom migration, selection and others as potential driving forces for both modes of cline formation. In addition, we address the potential role of the last glacial period in (1) creating isolating barriers, (2) the opening of unoccupied habitats for range extension, and (3) as a mechanism for thermal selection. While some evidence exists that at least one of the driving forces is selection, the extent to which it and other deterministic forces participate as opposed to various stochastic processes must await further analysis
Some aspects of prolactin and growth hormone biology in fishes and amphibians are considered, including the nature of the secretory cells, the regulation of their activity, the chemistry of the hormones, and their physiological activity in relation to hydromineral metabolism and to growth and development. Inasmuch as most of the information is derived from only a small number of teleost and amphibian species, a broad evolutionary biology is difficult to derive without information from other fish groups especially, and a survey must be confined largely to a comparative biology of some representative higher bony fishes with some representative anurans and urodeles.
SYNOPSIS. The fundamental evolutionary position of the fishes and the plasticity of their gene expression render them well suited for developmental genetic analyses. Isozymes, encoded in related loci, have proven to be effective probes of differential gene expression in the fishes. The advanced bony fishes exhibit a higher temporal and spatial specificity of isozyme locus expression than the primitive fishes. Some isozyme loci are limited in their expression to specific developmental periods such as hatching. The more phylogenetically recently derived loci have a more restricted tissue expression, and tend to be expressed later in development than more ancient loci exhibiting a more generalized tissue expression. More closely related isozyme loci tend to overlap more in their cellular expressions than do more distantly related loci. The role of gene and genome relatedness in regulating gene expression also has been studied by the investigation of preferential allele expression in interspecific hybrids. The schedules of gene expression are often perturbed in interspecific fish hybrids. A progressive increase in the severity of developmental abnormalities, at the morphological and enzymatic levels, occurs during embryogenesis of hybrids formed from progressively more distantly related species. In most instances of allelic repression, the paternal allele is preferentially inhibited but occasionally the maternal allele is selectively repressed. A non-reciprocal developmental success is often observed for hybrid embryos derived from reciprocal crosses. These aberrant nucleocytoplasmic interactions have been related to models of gene regulation and the evolutionary divergence of gene regulatory mechanisms.
A major question in the analysis of teleost epiboly is the fate of the yolk cytoplasmic layer. It diminishes during epiboly and eventually disappears at the completion of epiboly. This paper is concerned with the fate of the surface of the yolk cytoplasmic layer during epiboly. When gastrulae during epiboly are bathed in lucifer yellow (CH) and then observed with fluorescent microscopy or bathed in ferritin and then fixed and observed with TEM, a thin circumferential ring of endocytic vesicles is observed, confined to the external yolk syncytial layer just peripheral to the advancing margin of the blastoderm. Even though the entire egg is immersed in the marker, endocytosis is confined to this limited region. More precisely, this endocytosis occurs only within the region of the external yolk syncytial layer, where the surface is most folded. The endocytic vesicles thus formed move downward and settle on the surface of the membrane separating the yolk from the cytoplasm in the yolk syncytial layer. They do not join the surface of the internal yolk syncytial layer; hence they do not contribute to its expansion. Prior to the onset of epiboly there is no such endocytosis at the surface of the egg. Since this endocytosis occurs only during epiboly and only at the surface of the external yolk syncytial layer just peripheral to the advancing margin of the blastoderm, and in the absence of large molecules in the medium, we conclude that it is programmed. We, therefore, present this as a case of programmed internalization of cell surface serving as the morphogenetic mechanism responsible for the disappearance of the surface of the yolk cytoplasmic layer during gastrulation of the teleost Fundulus heteroclitus
Comparison of oncogene sequences from divergent species is an important step toward understanding the evolution and function of cellular oncogenes in neoplasia. We initiated our studies on oncogenes in lower vertebrates by cloning and sequencing the c-myc gene from rainbow trout (Salmo gairdneri).1 The trout c-myc gene shows extensive homology to exons II and III of the c-myc gene of chicken and human. The greatest homology among these three genes is localized to two specific regions within exon II. Fish, chicken and human each have unique inserted regions in the second exon. Other than these insertions, the second and third exons appear to have evolved gradually by the accumulative acceptance of point mutations. The rainbow trout myc gene was used as a probe in Southern blot analysis to screen DNA from teleost tumors for amplification, translocation and/or rearrangements of myc. We found no evidence that such changes had occurred in myc, or other oncogenes, in the fish tumors we examined. Transfection assays to isolate other teleost transforming genes have identified two types of foci while some transfected cells have generated tumors in athymic mice.
Nearly 40 years ago, Sperry postulated that neurones bear markers indicating their positions within the larger brain areas and that these are matched with similar position-dependent markers on other neurones to direct the formation of topographic projections. His hypothesis has guided several decades of intensive investigations. While most studies indicate that each fibre does not seek out a marked post-synaptic site, it appears likely that there are markers on fibres which are used instead to maintain order along the pathways. Each fibre would use them to keep its place in the topographic presynaptic array while competing with the other fibres for available post-synaptic sites.
cDNA clones encoding chum salmon (Oncorhynchus keta) growth hormone (sGH) have been isolated from a cDNA library prepared from chum salmon pituitary gland poly(A)+ RNA. Synthetic oligodeoxynucleotide mixtures based on amino acid residues 23-28 of sGH were used as hybridization probes
to select recombinant plasmids carrying the sGH coding sequence. The complete nucleotide sequence of sGH cDNA has been determined.
The cDNA sequence codes for a polypeptide of 210 amino acids, including a putative signal sequence of 22 amino acids. The
5′ and 3′ untranslated regions of the message were 64 and 426 bases long, respectively. Mature sGH was efficiently expressed
in Escherichia coli carrying a plasmid in which the sGH cDNA was under control of the E. coli trp promoter; sGH comprised about 15% of the total cellular protein in such bacteria. The partially purified sGH from E. coli stimulated the growth of rainbow trout and the activity was indistinguishable from that of natural sGH.
The experimental introduction of novel gene sequences into various fish species is discussed and the longer term outlook for such work appraised. Current methods are critically discussed, together with the various possible fates of the inserted novel sequences. Some positive results from our two laboratories are presented, together with an indication of parallel work being pursued in other laboratories.
DNA which contained the E. coli β-galactosidase gene fused to the mouse metallothionein promoter was microinjected into fertilized ova from Atlantic salmon (Salmo salar). Nine to 14 weeks later, embryos which derived from the injected ova were shown to express β-galactosidase activity. The DNA which had been microinjected into the ova was also present in some embryos after 14 weeks development. It was not possible to show if the injected DNA had in fact integrated into the chromosomes. This study provides evidence for the functioning of the mouse metallothionein promoter in vivo in salmon embryos.
Novel gene which was microinjected into fertilized eggs of the goldfish replicated during the embryogenesis. A proportion of the novel gene has been integrated into the host DNS of the 50-day-old transgenic goldfish.
Bei bestimmten Zahnkarpfen-Bastarden treten stets erbbedingte Melanome auf. Diese entstehen dadurch, dass bestimmte Gene, die fr die Differenzierung von Farbzellen verantwortlich sind, enthemmt und gleichzeitig zu einer gesteigerten Aktivitt angeregt werden. Die Enthemmung beruht auf einem Verlust bestimmter Repressionsgene und die Aktivittssteigerung auf einer Einfhrung polyfaktorieller Systeme von Induktionsgene. Es bestehen schwerwiegende Indizien dafr, dass die Induktorsubstanzen mit Aminosuren identisch sind.
This review of the literature on neoplastic or cancer-like disorders in fish and shellfish sets out to (1) summarize what is known of the occurrence of neoplastic diseases in indigenous populations of aquatic animals found in different geographic areas of the world; (2) critically evaluate existing reports so as to determine whether or not environmental pollutants are implicated as causal agents of the cellular disorders and (3) describe the current state of knowledge in the general areas of fish and shellfish metabolism and the use of aquatic animal models in studies of chemical carcinogenesis.
A plasmid containing human growth hormone cDNA sequence was injected into cytoplasm of fertilized rainbow trout (Salmo gairdneri Rich.) eggs before first cleavage. Survival rates at hatching (stage of analysis) were high (average: 77%; range: 50–100%). Foreign DNA was detected in pooled and individual embryos either by dot blot or by southern electrophoresis procedures using the labelled plasmid as probe; it comigrated with the high molecular weight DNA and was therefore most likely integrated in the trout genome. Transformation yields were higher with linearized than with circular plasmid (75% versus 40%). These data suggest that transgenic trout can be routinely obtained in large proportions.
We cloned ras-related sequences from goldfish genomic libraries constructed as recombinants using the λ phage. Restriction enzyme mapping of the clones obtained revealed three kinds of ras-related sequences among approximately 350,000 genomic clones. One of these clones was partially sequenced. Comparison with the nucleotide sequences of mammalian ras genes showed that the determined sequences covered the predicted amino acid coding regions and parts of the intervening regions. The predicted amino acid sequences of the cloned ras-related goldfish gene suggested that the coding region is localized separately in DNA, and that its exon-intron boundaries are exactly the same as those of corresponding mammalian genes. The nucleotide and amino acid sequences of the goldfish ras-related gene may have extensive homologies to mammalian p 21 protein. Among the three mammalian ras proteins, the predicted amino acid sequence of the sequenced ras-related goldfish clone is most closely homologous (96%) to the Kirsten ras protein. Differences in the predicted amino acid sequence were greatest in the sequence predicted from the fourth exon; fewer differences were found in the sequence from the third exon, and only slight or no differences were found in the sequence predicted for the first and second exons. The 12th and 61st amino acids from the N-terminal of the protein, which are thought to be critical positions for GTP binding and catalysis, are both conserved in the goldfish protein. Bearing in mind the evolutionary time of the divergence of fish from mammals (3.5–4.0 × 108 years ago), the extensive conservation of the amino acid sequence in the goldfish ras protein suggests that this protein may play an important role in cell homeostasis.
Among survivors of experimental infection of herpesvirus OMV which was considered to be a new viral pathogen of salmonids producing hepatic necrosis and significant mortality, more than 60% developed tumors. The perioral maxillary and mandibular region are the most frequent site of tumor formation. In decreasing order of frequency, tumors were also found on the caudal fin, gill-cover, eye, and kidney. Histopathologically the tumors were composed of abundantly proliferative, well differentiated epithelial cells supported by fine connective tissue stroma. Although virus particles were not observed in tumor cells, OMV isolation was successful from a tumor tissue sample that appeared necrotic on day 275 postinfection and from primary cultures of a tumor tissue from another fish sampled 296 days postinfection. From the evidence thus far obtained, OMV is considered to be a new pathogenic and oncogenic salmon virus. It is the first oncogenic agent to be isolated from fish.
Starch gel electrophoresis has shown that natural populations of Fundulus heteroclitus have electrophoretic variants for at least 21 loci. We provide inheritance data for 10 polymorphic systems: esterases ( Est-B , EST-C, and Est-D ); aspartate amlnotransferases ( Aat-A , and Aat-B ); mannosephosphate isomerase ( Mpl-A ); acid phosphatase ( Ap-A ); phosphoglucomutase ( Pgm-B ); hexose-6-phosphate dehydrogenase ( H6pdh-A ); and fumarase ( Fum-A ). Variants for nine of these loci segregate as autosomally inherited codominant alleles. The other system, EST-C, does not reflect such inheritance. We have identified two possible linkage groups: H6pdh-A may be loosely linked to Pgm-B , and Fum-A appears to be linked to Pgm-A . Tissue specificity and intracellular localization for all these loci are also presented.
This paper summarizes evidence for the following picture of Fundulus epiboly, with an eye toward laying groundwork for future investigation. The major force in epiboly is the yolk syncytial layer (YSL). Prior to epiboly, it spreads well beyond the border of the blastoderm to form the wide external YSL (E-YSL). This has contractile properties, which, however, are restrained prior to epiboly by the attached enveloping layer (EVL) of the blastoderm. Epiboly begins when the E-YSL contracts and narrows, throwing its surface into folds and pulling the internal YSL (I-YSL) and the attached EVL vegetally. When the narrowing of the E-YSL has ceased, it is postulated that its contractility continues as a circumferential wave of vegetally directed contraction that moves over the yolk toward the vegetal pole, dragging the I-YSL and the attached EVL (and blastoderm) with it. The most obvious visible manifestation of this wave is a marked marginal constriction, where the YSL joins the yolk cytoplasmic layer (YCL). As this contractile wave passes over the yolk, cytoplasm from the YCL mingles with that of the advancing E-YSL, and YCL surface adds to the already highly convoluted surface of the E-YSL. This folded surface is the site of a thin, highly localized band of rapid endocytosis that encircles the egg and passes over it with the E-YSL in a wave throughout epiboly. This internalization, which is receptor independent and therefore somehow programmed, accompanies the putative contractile wave, and accounts for the disappearance of the surface of the YCL. Since the YCL surface stands in the way of the advancing YSL, its internalization is part of the mechanism of epiboly. As the I-YSL expands in response to this marginal pull, its abundant microvilli gradually disappear, providing surface for its epiboly. The firmly attached EVL likewise expands toward the vegetal pole in response to the pull of the autonomously expanding YSL. As epiboly of the EVL progresses, it adjusts to the geometric problems posed by a sheet expanding over a sphere by active cell rearrangement within the cell monolayer. Thus, epiboly of the EVL has an active as well as a passive component. Deep cells are not causally involved in epiboly, but move about in coordinated ways in the constantly increasing space between the I-YSL and the EVL provided by epiboly and form the germ ring and the embryonic shield and eventually the embryo proper. An attempt is made to pull all of this together, and more, in order to achieve as comprehensive an understanding of epiboly as present evidence will allow.
THE northern pike (Esox lucius) is a highly prized freshwater fish, both
as a game fish and as a commerical species. Epizootics of lymphosarcoma
occur widely in North American pike1 and in the Old
World2,3. The tumour in pike has been found with an overall
frequency of 20.9%, which is the highest frequency of a malignant
neoplasm in any known free living vertebrate1. All pike with
the tumour have cutaneous lesions, and epizootiological evidence
suggests that the disease is transmitted horizontally by contact during
spawning1. The tumour is transplantable and evidence of
cell-free transmission has been found1,4. In an attempt to
resolve the aetiology of the disease, we have investigated the presence
of oncornavirus in pike lymphoma. Since all known RNA tumour viruses
possess the enzyme reverse transcriptase, we have sought the activity of
this enzyme in post-mitochondrial particulate fractions prepared from
pike lymphoma tissue.
Liver neoplasms including trabecular hepatoma and cholangioma were induced in medakas (Oryzias latipes) by the addition of methylazoxymethanol acetate to their aquarium water at levels of 0.1-3 ppm for periods ranging from 1 to 120 days. More than 80% of the surviving fish developed tumors at 3 or 5 months after commencement of the treatment, irrespective of levels of the drug, when appropriate times of exposure were chosen.
Liver cancer appeared in domesticated rainbow trout in many fish hatcheries in the USA from 1957 to 1960. This unexpected disease outbreak reached epizootic proportions. Viruses, pesticides, and herbicides were suggested as possible causes, but at that time there was taking place a marked change in fish husbandry. Formerly, trout diets consisted of a 'wet' mixture of slaughterhouse by-products, with raw fish and horsemeat. Economic factors forced a change to a 'dry' pelleted food composed of a combination of fish, meat, and vegetable meals combined with a mixture of essential vitamins and minerals. By solvent extraction and thin-layer chromatography, Engebrecht et al. isolated from the toxic cottonseed meal a fluorescent substance and established by chemical tests and duckling assay that the compound was aflatoxin B1 (AFB). The same lesions were seen, however, with orally administered dimethylnitrosamine and cyclopropenoid fatty acids (CPFA), so it appears that the trout responds in a similar manner to different types of hepatic carcinogens, as does the rat. CPFA result in typical mature carcinomas, but there are additional preneoplastic nodular stages, the significance of which is unknown. The pathogenesis of CPFA-induced carcinogenesis needs to be studied in much greater detail. This brief review indicates that there is much which is presently not known about the pathogenesis of rainbow trout liver tumors. In particular, there is a need to investigate the histochemical characteristics of trout livers early in the carcinogenic process, to manipulate carcinogen application in an attempt to induce early morphologically recognizable preneoplastic lesions, to experiment with a greater spectrum of recognized liver carcinogens, and to further develop the trout egg-carcinogen bath method as a tool to understand the dynamics of one-dose carcinogenesis. ( 82 references).
Natural populations of Fundulus heteroclitus show extensive spatial variation in gene frequencies at four unlinked polymorphic loci. Large clinal changes in gene frequencies were found for Ldh-B, Mdh-A, and Gpi-B, whereas the spatial variation for the Pgm-B locus was small. Since the geographical area over which these clines are found is characterized by a steep thermal gradient, the clines in gene frequency are correlated with a directional change in mean water temperature. Maximum gene diversity of these four loci was correlated with annual fluctuations in water temperature. Temporal stability of the allelic frequencies was established for a 2--4 year period.
Electrophoretic analysis has shown populations of F. heteroclitus to possess variants at four enzyme-coding loci: Ldh-B, Mdh-A, Gpi-B, and Pgm-A. Based on the phenotypic distribution in the F1 generation, each variant segregates as an autosomally inherited codominant allele. A pairwise comparison of the expected phenotypic classes among these loci showed no evidence of strong linkage; however, weak linkage could not be ruled out. Despite the considerable genetic divergence of populations from the geographical extremes of this species, offspring resulting from crosses between individuals from these localities show viabilities similar to those found for crosses of local populations.