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d-rR strain female medaka. (A) Female medaka (Xr')() are identified genotypically by sexlinked inheritance of white pigmentation and phenotypically by development of secondary sexual characteristics. (B) Secondary female sexual characteristics include rounded dorsal fin (rd), triangular anal fin (ta), and bilobed bulbous genital papillae (gp).
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Complete sex reversal of fish is accomplished routinely in aquaculture practices by exposing fish to exogenous sex steroids during gonadal differentiation. A variety of environmental chemicals are also active at sex steroid receptors and theoretically possess the potential to alter normal sexual differentiation in fish. However, in controlled envir...
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... fish was fully anesthetized in 0.1% MS-222 (ethyl m-aminobenzoate; Sigma). We then examined fish with a stereoscope microscope (M5; Wild, Heerbrugg, Switzerland) to determine pigmentation and to score for male and female external secondary sexual characteristics (Figures 1 and 2). After scor- ing, the midsection of each fish was dissected for gonad analysis. ...
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Cigarette smoke exposure during prenatal and early postnatal periods increases the incidence of a variety of abnormal behaviors later in life. The purpose of this study was to identify the possible critical period of susceptibility to cigarette smoke exposure and evaluate the possibe effects of cigarette smoke during early life on brain...
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... Another route of exposure used to assess endocrine disrupting effects of DDT on medaka gonadal development was direct injection of embryos to model maternal deposition of DDT into lipophilic structures of the embryo. Edmunds et al. (2000) microinjected 0 days post fertilization (dpf) medaka yolk sacs with doses ranging from 19.6 to 1079 ng o, p'-DDT/egg (Edmunds et al., 2000). At 10 weeks post-injection, sex reversal was only identified in fish injected with 227 ng/egg (all fish at higher doses of 580 and 1079 ng/egg died by 10 weeks and no sex reversal was observed in lower doses of 19.6 and 33 ng/egg). ...
... Another route of exposure used to assess endocrine disrupting effects of DDT on medaka gonadal development was direct injection of embryos to model maternal deposition of DDT into lipophilic structures of the embryo. Edmunds et al. (2000) microinjected 0 days post fertilization (dpf) medaka yolk sacs with doses ranging from 19.6 to 1079 ng o, p'-DDT/egg (Edmunds et al., 2000). At 10 weeks post-injection, sex reversal was only identified in fish injected with 227 ng/egg (all fish at higher doses of 580 and 1079 ng/egg died by 10 weeks and no sex reversal was observed in lower doses of 19.6 and 33 ng/egg). ...
... In summary, while the dose required to induce intersex morphologies varies across studies, they provide a general range at which gonadal sex is permanently altered by o,p'-DDT. It appears that consistent aqueous exposure to approximately 2-5 ppb o,p'-DDT during gonadal differentiation in the first month of life generally induces intersex or sex reversal in 50% of fish subjects ( Fig. 2) (Edmunds et al., 2000). ...
... Some OCPs show estrogenic chemicals when vertebrates, including humans, undergo sensitive sex determination stages [260]. In fact, following a single pulse of the chemical into the egg, there was a complete change of male to female sex for ten weeks [275]. ...
Endocrine-disrupting chemicals (EDCs) are a growing public health concern worldwide. Consumption of foodstuffs is currently thought to be one of the principal exposure routes to EDCs. However, alternative ways of human exposure are through inhalation of chemicals and dermal contact. These compounds in food products such as canned food, bottled water, dairy products, fish, meat, egg, and vegetables are a ubiquitous concern to the general population. Therefore, understanding EDCs' properties, such as origin, exposure, toxicological impact, and legal aspects are vital to control their release to the environment and food. The present paper provides an overview of the EDCs and their possible disrupting impact on the endocrine system and other organs.
... In case of sea lampreys Petromyzon marinus, exposure to 3-trifloromethyl-4-nitrophenol (TFM) induced a female biased sex differentiation, thereby altered the sex ratio (Purvis, 1979). Sex inversion occurred in a large population of XY embryo of Japanese medaka when eggs/juveniles were treated with EE2 or DDT (Edmunds et al., 2000;Scholz & Gutzeit, 2000). Similarly, newly hatched Japanese medaka when exposed to sublethal concentrations of BPA exhibited the absence of males. ...
Among vertebrates, teleosts display a wide array of sex determination and differentiation mechanisms ranging from chromosomal sex determination on one end of the spectrum to environmental sex determination on the other end. However, the interplay of both these mechanisms is also not uncommon. Several gonochoristic fishes exhibit gonadal plasticity often resulting in sex reversal. The major manipulation of sex differentiation in teleost is affected by sex steroids. In this context, the increasing contamination of aquatic ecosystems by estrogen-like compounds, commonly known as xenoestrogens, is of major concern. This often leads to deleterious effects on the reproductive success of fish and thereby adversely impacts aquatic biodiversity. In the present review, we have focused on impact of xenoestrogen at different levels of the reproductive system influencing not only gonadal differentiation in teleosts but also their reproductive functions. The review would also explore the mitigation strategies and regulations in place for aquatic xenoestrogen management.
... Such sex reversal could lead to skewing of sex ratios towards one phenotype and eventually extinction of the species. Previous reports have shown that developmental exposure to endocrine disruptors [23,24] or pesticides [25,26] can induce persistent effects that manifest in adulthood [27]. Hence, our data indicated that nWh could be potentially hazardous to GC development and, thereby, reproduction in XY medaka. ...
Whitlockite (WH), the second most abundant bone mineral was found promising in regenerative engineering of damaged bone tissue because of its high bone remodelling potential. However, no studies have investigated its effects on other organ systems and environment. It is important to study this aspect as WH is known to dissolute at non-acidic pH. Hence, the effects of WH nanoparticles (nWh) on embryonic development, germ cell (GC) differentiation and gametogenesis were explored here in an aquatic species, the Japanese medaka. Exposure to nWh of 59.67±10.21 nm size showed no impact on development, survivability and hatchability of medaka embryos. However, nWh caused an increase in germ cell count in a significant number of XY males exposed to 0.1 mg L-1 in comparison to that of untreated controls and larvae exposed to 0.01, 1 and 10 mg L-1. Interestingly, XX females exposed to nWh showed no such effect. Exposure to nWh at stages after attaining sexual maturity did not have any effects on the reproductive systems of medaka males and females. Importantly, this study revealed that germ cell development during embryonic period was sensitive to nWh exposure, warranting detailed analyses and more studies in this regard using these particles.
... Methimazole induced female biased sex ratio was not reversed after a short period of depuration <15 days (observation at 45 dpf), but was reversed after a long period of depuration (observation at 60 dpf) (Sharma and Patiño, 2013;Dang and Kienzler, 2019). As shown in Table 4, several TDCs including o, p'-DDT (Edmunds et al., 2000), PFAAs (Lee et al., 2017), PFOS (Du et al., 2009;Wang et al., 2011), tetrabromobisphenol A (Chen et al., 2016;Kuiper et al., 2007) and tribromophenol changed sex ratio in zebrafish and in medaka. Among these studies on sex ratio, PFOS, for example, changed sex ratio in zebrafish in one study (Wang et al., 2011) but not in another study (Du et al., 2009). ...
Identification of thyroid disrupting chemicals (TDCs), one of the most studied types of endocrine disruptors (EDs), is required according to EU regulations on industrial chemicals, pesticides, and biocides. Following that requirement, the use of fish as an unique non-mammalian model species for identification of EDs may be warranted. This study summarised and evaluated effects of TDCs on fish thyroid sensitive endpoints including thyroid hormones, thyroid related gene expression, immunostaining for thyroid follicles, eye size and pigmentation, swim bladder inflation as well as effects of TDCs on secondary sex characteristics, sex ratio, growth and reproduction. Changes in thyroid sensitive endpoints may reflect the balanced outcome of different processes of the thyroid cascade. Thyroid sensitive endpoints may also be altered by non-thyroid molecular or endocrine pathways as well as non-specific factors such as general toxicity, development, stress, nutrient, and the environmental factors like temperature and pH. Defining chemical specific effects on thyroid sensitive endpoints is important for identification of TDCs. Application of the AOP (adverse outcome pathway) concept could be helpful for defining critical events needed for testing and identification of TDCs in fish.
... Second, we found three clutches that were likely sired by XX males: 17, 12 and 9 laboratory-raised animals that were randomly chosen as eggs from three clutches, respectively, were all XX individuals, which would have a very low chance of happening merely by accidental sampling if these clutches had the theoretically expected 1:1 sex ratio (ca. 10 -6 to 10 -3 probability). Sex-reversed individuals were found to be fertile in some ectothermic vertebrates (Devlin & Nagahama, 2002;Edmunds, McCarthy, & Ramsdell, 2000;Holleley et al., 2015), and in common frogs, XX males appear to be fertile and as successful in mating as XY males (Alho et al., 2010;Veltsos et al., 2019). If sex-reversed individuals do reproduce in nature, the biased sex ratios of their progeny may lead to changes in the population sex ratio, sex chromosome frequencies and ultimately the sex-determination system (Bókony et al., 2017;Quinn, Sarre, Ezaz, Marshall Graves, & a, & Georges, A., 2011;Wedekind, 2017). ...
Populations of ectothermic vertebrates are vulnerable to environmental pollution and climate change because certain chemicals and extreme temperatures can cause sex reversal during early ontogeny (i.e. genetically female individuals develop male phenotype or vice versa), which may distort population sex ratios. However, we have troublingly little information on sex reversals in natural populations, due to unavailability of genetic sex markers. Here we developed a genetic sexing method based on sex‐linked single nucleotide polymorphism loci to study the prevalence and fitness consequences of sex reversal in agile frogs (Rana dalmatina). Out of 125 juveniles raised in laboratory without exposure to sex‐reversing stimuli, 6 showed male phenotype but female genotype according to our markers. These individuals exhibited several signs of poor physiological condition, suggesting stress‐induced sex reversal and inferior fitness prospects. Among 162 adults from 11 wild populations in North‐Central Hungary, 20% of phenotypic males had female genotype according to our markers. These individuals occurred more frequently in areas of anthropogenic land use; this association was attributable to agriculture and less strongly to urban land use. Female‐to‐male sex‐reversed adults had similar body mass as normal males. We recorded no events of male‐to‐female sex reversal either in the lab or in the wild. These results support recent suspicions that sex reversal is widespread in nature, and suggest that human‐induced environmental changes may contribute to its pervasiveness. Furthermore, our findings indicate that sex‐reversal is associated with stress and poor health in early life, but sex‐reversed individuals surviving to adulthood may participate in breeding.
... Another study reported that the prenatal exposure (median concentration of 1.2 ng/g lipid) during pregnancy was associated with several adiposity measures in boys [34]. In wildlife, in vivo studies have shown that o,p -DDT can induce intersex in Japanese medaka at much higher exposure concentrations (5−50 µg/L) [35,36]. These studies indicate that the potential toxic concentration of o,p'-DDT for wildlife and humans are at ng/mL level (sub-micro mole level). ...
The compound 1,1,1-trichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl) ethane (o,p’-DDT) has been identified as one of the endocrine-disrupting chemicals causing adverse effects on wildlife and even humans through bioaccumulation. Its detection has become increasingly important. We have obtained candidate aptamers binding to o,p’-DDT by a systematic evolution of ligands by exponential enrichment (SELEX) protocol. Five out of seventeen candidate sequences were selected for preliminary characterization by SYBR Green I assay. One sequence with highest fluorescence response with o,p’-DDT, designated DDT_13, was chosen for further characterization. Its dissociation constant (Kd) was determined to be 412.3 ± 124.6 nM. DDT_13 exhibited low cross-binding activities on other tested small molecules. The good bioactivities of DDT_13 were demonstrated for the analysis of spiked lake water and tap water samples. This study provides a novel o,p’-DDT-specific probe for its future applications.
... Moreover, inhibition of aromatase activity can cause sex reversal in fish [83,84]. Some environmental pollutants, such as pesticides, have been shown to affect sex conversion of fish [85,86]. Here, dimethoate treatment can improve the transcriptional level of the Psi_CYP19A1 gene, suggesting a potential effect of sex conversion. ...
Cytochrome P450s (CYPs) are a family of membrane-bound mono-oxygenase proteins, which are involved in cell metabolism and detoxification of various xenobiotic substances. In this study, we identified 58 putative CYP genes in Amur stickleback (Pungitius sinensis) based on the transcriptome sequencing. Conserved motif distribution suggested their functional relevance within each group. Some present recombination events have accelerated the evolution of this gene family. Moreover, a few positive selection sites were identified, which may have accelerated the functional divergence of this family of proteins. Expression patterns of these CYP genes were investigated and indicated that most were affected by dimethoate treatment, suggesting that CYPs were involved in the detoxication of dimethoate. This study will provide a foundation for the further functional investigation of CYP genes in fishes.
... Neither canola oil nor DMSO affected any of the toxicity endpoints. Dimethylsulfoxide has already been used for the injection of zebrafish embryos in previous studies (Maes et al. 2012;Schubert et al. 2014;Li et al. 2015), but triolein is the more commonly used solvent in injection studies with fish embryos (Edmunds et al. 2000;Hano et al. 2005;Nassef et al. 2010;Schubert et al. 2014;Xiao et al. 2017). Our results, however, showed that the use of triolein can lead to effects on survival and heart rate. ...
... Because the size and structure of the eggs differ among fish species, the ideal droplet size could be species specific. Droplet sizes between 1 and 3 nL were, for example, reported for medaka embryos (Edmunds et al. 2000). ...
Fish (embryo) toxicity test guidelines are mostly based on aquatic exposures. However, in some cases, other exposure routes can be more practical and relevant. Micro‐injection into the yolk of fish embryos could offer a particular advantage for administering hydrophobic compounds, such as many endocrine disruptors. Single dose micro‐injection was compared to continuous aquatic exposure in terms of compound accumulation and biological responses. 17α‐ethinyl estradiol (EE2) was used as a model compound. First, the optimal solvent and droplet size were optimized, and needle variation was assessed. Next, biological endpoints were evaluated. The accumulated internal dose of EE2 decreased over time in both exposure scenarios. Estrogen receptor (ER) activation was concentration/injected dose dependent, increased daily and was related to esr2b transcription. Vtg1 and cyp19a1b transcription was induced in both scenarios, but the cyp19a1b transcription pattern differed between routes. Injection caused an increase of cyp19a1b transcripts from 48 hours post fertilization (hpf) onwards, while after aquatic exposure the main increase occurred between 96 and 120 hpf. Some malformations only occurred after injection, while others were present for both scenarios. We conclude that responses can differ between exposure routes and therefore micro‐injection is not a direct substitute for, but can be complementary to aquatic exposure. Nevertheless, vtg1 and cyp19a1b transcription and ER activation are suitable biomarkers for endocrine disruptor screening in both scenarios. This article is protected by copyright. All rights reserved
... Regarding the effect of EDCs exposure on fish sex ratio, some species are also more sensitive than others, i.e., while the in some species feminization or masculinization can be reversible, in others once sex is determined it remains unaltered. For instance, estrogenic exposure during gonadal differentiation in differentiated gonochorists, such as fathead minnow (Pimephales promelas) and medaka (Oryzias latipes), leads to complete sex reversal, from male-to-female (Edmunds et al., 2000;Iwamatsu et al., 2005;Länge et al., 2001). By the contrary, undifferentiated gonochorist fish, like zebrafish, have a gonad development more plastic and therefore are able to resume gonads development according to their genetic sex once estrogen exposure has stopped (Fenske et al., 2005;Maack and Segner, 2004). ...
Zebrafish (Danio rerio) is extensively used in research; however the mechanisms that control this species sex determination are still poorly understood. In the latest decades, it has been established that zebrafish sex is determined by genetic factors on a polygenic basis, as various candidate genes with sex dimorphic expression, as well sex-linked loci have been identified in different zebrafish strains. However, it has been evidenced that sex determination in this species is also influenced by environmental factors. For instance, temperature can have a crucial role in zebrafish sex determination. Likewise, the exposure to endocrine disrupting chemicals (EDCs), the most studied zebrafish sex changing factor, can strongly influence the course of sex differentiation and unbalance the sex ratio of zebrafish populations. Despite this, so far the influence of environmental factors is still less understood and only few studies have addressed this topic. Therefore, this review intends to gather current knowledge on the environmental factors involved in sex determination of zebrafish and identify important gaps in this research area. Briefly, the current understanding on zebrafish sex related genetics is also addressed.
