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Longitudinal gill cross-sections. Secondary lamellae from infected fish showed a strong increase in secretory cells, which was appreciably higher at the distal end of the primary lamellae (stained blue or purple) containing neutral and acids mucopolysaccharides. a-c) Alcian blue, d) Periodic acid Schiff. a) Control fish, and b,c,d) infected fish. Scale bar: 20 µm (c) and 60 µm (d).
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The purpose of this study was to characterize histopathological changes induced by the sea louse Caligus rogercresseyi in juvenile individuals of rainbow trout (Oncorhynchus mykiss). Specific effects were determined for mucus-secreting cells, mast cells/eosinophilic granule cells (MCs/EGCs) and activation of pro-inflammatory caspase-1, which are in...
Contexts in source publication
Context 1
... to the primary lamellae (Figs. 2a, 2c). Moreover, at the primary lamellae of the infected fish, the connective tissue showed an increased quantity of MCs/EGCs, monocytes/macrophage, and lymphocytes (Figs. 2e- 2f). Furthermore, infected-fish gills presented an increase in mucus-secreting or goblet cells in the epithelium of secondary lamellae (Figs. 3a-3b) and the distal tip of the gill filaments (Figs. ...
Context 2
... at the primary lamellae of the infected fish, the connective tissue showed an increased quantity of MCs/EGCs, monocytes/macrophage, and lymphocytes (Figs. 2e- 2f). Furthermore, infected-fish gills presented an increase in mucus-secreting or goblet cells in the epithelium of secondary lamellae (Figs. 3a-3b) and the distal tip of the gill filaments (Figs. ...
Context 3
... to the primary lamellae (Figs. 2a, 2c). Moreover, at the primary lamellae of the infected fish, the connective tissue showed an increased quantity of MCs/EGCs, monocytes/macrophage, and lymphocytes (Figs. 2e- 2f). Furthermore, infected-fish gills presented an increase in mucus-secreting or goblet cells in the epithelium of secondary lamellae (Figs. 3a-3b) and the distal tip of the gill filaments (Figs. ...
Context 4
... at the primary lamellae of the infected fish, the connective tissue showed an increased quantity of MCs/EGCs, monocytes/macrophage, and lymphocytes (Figs. 2e- 2f). Furthermore, infected-fish gills presented an increase in mucus-secreting or goblet cells in the epithelium of secondary lamellae (Figs. 3a-3b) and the distal tip of the gill filaments (Figs. ...
Citations
... An inflammatory response was observed, which, depending on the degree of progression of the lesion, was extended from the dermis to the hypodermis, accompanied by a significant loss of scales and leukocyte infiltration [4,5,26,27]. The observed inflammatory response indicates the activation of an innate immune response in the lesions [27][28][29]. This type of reaction constitutes a defensive response, as the inflammatory process aims to protect the host by eliminating the pathogens [14,17]. ...
Aquaculture plays a crucial role in addressing the growing global demand for food. However, diseases associated with intensive aquaculture practices, especially those affecting the skin, can present significant challenges to both fish health and the industry as a whole. Strawberry disease (SD), also known as red-mark syndrome, is a persistent and non-lethal skin condition observed in Rainbow Trout (Oncorhynchus mykiss) in the United States and various European countries. SD is a nonlethal skin condition of an unclear etiology that affects rainbow trout reared in freshwater close to the harvest period. We used a RNA-based approach to examine active microbiota in the SD skin lesions and compared to non-injured skin. Our results, based on using 16S rRNA gene next-generation sequencing, showed that the skin microbiota was dominated by the phyla Firmicutes, Proteobacteria, and Actinobacteria. The comparisons of the skin microbiota between injured and non-injured samples showed differences in the alpha diversity (Fisher index) and beta diversity metrics (ANOSIM). At the genus level, both Pseudomonas and Candidatus Midichloria were highlighted as the most abundant taxa detected in samples obtained from fish affected with strawberry diseases. In contrast, the most abundant taxa in non-injured skin were Escherichia-Shigella, Streptococcus, and Pseudoalteromonas. In conclusion, our study on SD revealed distinct differences in the microbiota composition between skin lesions and non-injured skin. This is the first description of microbiota associated with SD-injured skin samples using an RNA approach.
... However, the detection of sea lice in gills is not typical, although the immune response has been detected in this tissue during C. rogrecresseyi infestation [27,28]. Sea lice can produce an anti-inflammatory response, hyperplasia, thickening, and complete or partial lamellar fusion in fish gills even when they are not attached on it [29]. Simultaneously, the gills of infected fish show increased melanomacrophages centers/eosinophilic granule cells, monocytes/macrophages, and lymphocytes, with an increase in mucus production and globet cells [29]. ...
... Sea lice can produce an anti-inflammatory response, hyperplasia, thickening, and complete or partial lamellar fusion in fish gills even when they are not attached on it [29]. Simultaneously, the gills of infected fish show increased melanomacrophages centers/eosinophilic granule cells, monocytes/macrophages, and lymphocytes, with an increase in mucus production and globet cells [29]. Hence, gills are highly sensitive to Caligus infestation, being a good candidate for evaluating immune parameters. ...
The immune response of Atlantic salmon to sea lice has been extensively studied, but we
still do not know the mechanisms by which some fish become resistant and others do not. In this
study, we estimated the heritabilities of three key proteins associated with the innate immunity and
resistance of Salmo salar against the sea louse Caligus rogercresseyi. In particular, we quantified the
abundance of 2 pro-inflammatory cytokines, Tnf� and Il-8, and an antioxidant enzyme, Nkef, in
Atlantic salmon skin and gill tissue from 21 families and 268 individuals by indirect ELISA. This
covers a wide parasite load range from low or resistant (mean sea lice � SE = 8.7 � 0.9) to high or
susceptible (mean sea lice � SE = 43.3 � 2.0). Our results showed that susceptible fish had higher
levels of Nkef and Tnf� than resistant fish in their gills and skin, although gill Il-8 was higher in
resistant fish, while no significant differences were found in the skin. Furthermore, moderate to very
high heritable genetic variation was estimated for Nkef (h2 skin: 0.96 � 0.14 and gills: 0.97 � 0.11)
and Tnf� (h2 skin: 0.53 � 0.17 and gills: 0.32 � 0.14), but not for Il-8 (h2 skin: 0.22 � 0.12 ns and
gills: 0.09 � 0.08 ns). This work provides evidence that Nkef and Tnf� protein expressions are highly
heritable and related to resistance against sea lice in Atlantic salmon.
... Infestations by Caligus spp. can cause the mortality in wild fish populations (Chatterji et al. 1982, Hayward et al. 2008, 2009, Abdelkalek et al. 2021) and also result in economic losses due to mortality, reduced growth rate and poor feed conversion ratio among farmed fish populations (Rojas et al. 2018, Arriagada et al. 2019), leading to the use of chemical products to control and treat infestations in the hosts (Bravo et al. 2010, Hamre et al. 2011, Agusti et al. 2016, Arriagada & Marín 2018, Arriagada et al. 2019, 2020. ...
... The ultra-structural analysis of the skin from infected fish also showed collagen fiber disruption and an evident increase in subdermal melanophores. Rojas et al. (2018) and low to moderate intensity of Caligus species, in contrast to farmed fish, which had higher abundance and intensity. The prevalence, intensity and abundance of different species in the Caligus infracommunities sampled of the present study are clearly unequal. ...
... Histopathology is an excellent tool for evaluating the effects of parasites on host fish tissues (Easa & El-Wafa 1995, Rojas et al. 2018). Fish gills and skin have therefore been used as biomarkers in the evaluation of the health of fish infested by Caligus species in both laboratory and field studies. ...
This review surveyed information on Caligus Müller, 1785 to identify global infestation patterns and geographic distribution in teleost fishes, as well as physiological and histopathological data and description of treatment strategies. A total 990 samples of Caligus spp. (N = 212 species) obtained of 233 scientific papers on farmed and wild teleost species from 99 families and 30 orders were used, and the highest number of occurrences was on Carangidae. Caligus spp. was predominantly found in marine environments, and only Caligus lacustris and Caligus epidemicus were found in teleost fish of freshwater environments. There was a high prevalence of Caligus spp. on hosts and infestation occurred predominantly in both the tegument and the gills. Caligus species are distributed across different countries and some particularities were identified and discussed. Caligus elongatus and Caligus bonito bonito had the broadest geographic distribution. Histomorphological and hematological disorders caused by infestation by Caligus spp. were reported and discussed, as well as chemotherapeutic products used for controlling and treating the infestations. Variation in the distribution and geographic patterns of Caligus spp. were little evident in many ecosystems and due to the limited data on the infestation of these sea lice on teleost populations in different regions.
... Histopathology has been described in the tissues of rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) experimentally challenged with C. rogercresseyi (Rojas et al., 2018) with epidermal erosion, dermal hyperplasia, infammation in the stratum compactum and an increase in number of melanophores and epidermal mucous cells all reported. Rojas et al. (2018) also reported gill changes described as hyperplasia and fusion of the lamellae and increased quantities of infammatory and mucous cells. ...
... Histopathology has been described in the tissues of rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) experimentally challenged with C. rogercresseyi (Rojas et al., 2018) with epidermal erosion, dermal hyperplasia, infammation in the stratum compactum and an increase in number of melanophores and epidermal mucous cells all reported. Rojas et al. (2018) also reported gill changes described as hyperplasia and fusion of the lamellae and increased quantities of infammatory and mucous cells. Tere were also minor changes described in the intestine, such as disorganised epithelium and increased numbers of secretory cells, which the authors attributed to a systemic infammatory response in the trout to parasite infestation. ...
The parasitic crustacean copepods known as sea lice (Lepeophtheirus salmonis (Krøyer, 1837) and
Caligus spp.) have caused challenges for salmonids in both the wild and farmed fish arenas, but it has
been in the marine net pen farming of Atlantic salmon (Salmo salar L.) that the issues have been most
intense with wide-ranging impacts in fish welfare, farm production, economics, business opportunities
and local social licence (Johnson et al., 2004). This chapter reviews the pathologies observed,
induced and reported as associated with sea lice infestations on salmonids and will focus on the
clinical signs and gross pathology, histopathology, osmoregulatory effects and biochemistry as well as
stress responses, host impacts, healing and injuries associated with treatments.
... Porém, efeitos sistêmicos provocados por ectoparasitos também são registrados. Rojas et al. (2018) observaram resposta inflamatória generalizada em Oncorhynchus mykiss (truta-arco-íris) infestados pelo copépode Caligus rogercresseyi, com aumento de células inflamatórias em diferentes tecidos, como brânquias e intestino, embora a pele seja o sítio de infecção do parasito, demostrando assim, que ectoparasitos podem provocar reações sistêmicas no hospedeiro. Nos locais de fixação dos parasitos foram descritos vários graus de erosão e desorganização do epitélio até lesões da derme subjacente. ...
... Porém, efeitos sistêmicos provocados por ectoparasitos também são registrados. Rojas et al. (2018) observaram resposta inflamatória generalizada em Oncorhynchus mykiss (truta-arco-íris) infestados pelo copépode Caligus rogercresseyi, com aumento de células inflamatórias em diferentes tecidos, como brânquias e intestino, embora a pele seja o sítio de infecção do parasito, demostrando assim, que ectoparasitos podem provocar reações sistêmicas no hospedeiro. Nos locais de fixação dos parasitos foram descritos vários graus de erosão e desorganização do epitélio até lesões da derme subjacente. ...
... The few publications that show indications of damage to the collagen fibers of the dermis are linked to the analyses of fish postmortem, which tends to stiffen their musculature depending on the form of slaughter or even the method of preservation (Indrasena et al. 2000, Suárez et al. 2005). However, Rojas et al. (2018) noticed disorganization of the epithelium tissue in rainbow trout infected by Caligus rogercresseyi (Copepoda) -another fish ectoparasite crustacean -including rupture of the surface of the epithelium and the derangement of the cells of the dermal layer. These results corroborate the changes found in the specimens of the present study. ...
The main objective of this study was to evaluate the histological and hematological alterations of silver catfish Rhamdia quelen (Quoy & Gaimard, 1824) against intense parasitism by anchor worm Lernaea cyprinacea Linnaeus, 1758. Thirteen fish specimens were collected at the Fish Genetic Improvement Unit (EPAGRI/CEDAP), Brazil. After acclimatization, the fish were anesthetized for blood collection, and the samples were used for counting thrombocytes, total leukocytes, differential leukocytes and for quantification of total erythrocytes. Afterwards, the animals were euthanized, the parasites removed and quantified, and the portions of the affected tegument fixed in 10% buffered formalin. All the analyzed animals were parasitized by L. cyprinacea with mean intensity of 192 specimens per fish. The hematological profile of the animals was different from that reported for healthy fish. Immature leukocytes were the most abundant cells, followed by monocytes, lymphocytes, neutrophils, and periodic acid-Schiff-positive granular leukocytes. A small number of neutrophils were present in the bloodstream of parasitized fish, while histological examination evidenced the accumulation of this cell type near the place of infection by the parasite. Total leukocytes correlated significantly and positively (r = 0.6, p = 0.030) with the intensity of L. cyprinacea infection and the fish weight. Histological changes included hemorrhage, liquefactive necrosis and connective tissue disarrangement, necrosis, granulomatous inflammation, mononuclear and polynuclear inflammation, as well as hyperplasia and hypertrophy of the alarm and mucous cells. The L. cyprinacea infection intensity caused deleterious changes both in the hematological profile and the integument of R. quelen, confirming the pathogenic potential of this parasite to the affected fish species.
... The few publications that show indications of damage to the collagen fibers of the dermis are linked to the analyses of fish postmortem, which tends to stiffen their musculature depending on the form of slaughter or even the method of preservation (Indrasena et al. 2000, Suárez et al. 2005). However, Rojas et al. (2018) noticed disorganization of the epithelium tissue in rainbow trout infected by Caligus rogercresseyi (Copepoda) -another fish ectoparasite crustacean -including rupture of the surface of the epithelium and the derangement of the cells of the dermal layer. These results corroborate the changes found in the specimens of the present study. ...
The main objective of this study was to evaluate the histological and hematological alterations of silver catfish Rhamdia quelen (Quoy & Gaimard, 1824) against intense parasitism by anchor worm Lernaea cyprinacea Linnaeus, 1758. Thirteen fish specimens were collected at the Fish Genetic Improvement Unit (EPAGRI/CEDAP), Brazil. After acclimatization, the fish were anesthetized for blood collection, and the samples were used for counting thrombocytes, total leukocytes,
differential leukocytes and for quantification of total erythrocytes. Afterwards, the animals were euthanized, the parasites removed and quantified, and the portions of the affected tegument fixed in 10% buffered formalin. All the analyzed animals were parasitized by L. cyprinacea with mean intensity of 192 specimens per fish. The hematological profile of the animals was different from that reported for healthy fish. Immature leukocytes were the most abundant cells, followed by monocytes, lymphocytes, neutrophils, and periodic acid−Schiff-positive granular leukocytes. A small number of neutrophils were present in the bloodstream of parasitized fish, while histological examination evidenced the accumulation of this cell type near the place of infection by the parasite. Total leukocytes correlated significantly and positively (r = 0.6, p = 0.030) with the intensity of L.
cyprinacea infection and the fish weight. Histological changes ncluded hemorrhage, liquefactive necrosis and connective tissue disarrangement, necrosis, granulomatous inflammation, mononuclear
and polynuclear inflammation, as well as hyperplasia and hypertrophy of the alarm and mucous cells. The L. cyprinacea infection intensity caused deleterious changes both in the hematological profile and the integument of R. quelen, confirming the pathogenic potential of this parasite to the affected fish species.
Sea lice or salmon louse is the parasite with the highest economic impact on aquaculture of Atlantic salmon (Salmo salar) globally, which produced about 2.07 million tons (2014). Costs of sea lice are due to decrease in fish growth rate, increased feed conversion rate, and lower market value of fish with skin injuries plus the cost of treatment estimated at 305 million euros (2006). While sea lice includes Lepeoptheirus salmonis and Caligus elongatus, with Caligus rogercresseyi occurring in Canada and Chile or C. teres in Chile, L. salmonis is the key parasite on account of its specificity to salmonids, larger size, and high abundance. Severe infestations of L. salmonis produce deep erosions of the epidermis, dermis, and skeletal muscle in farmed fish. Damages to fish include dermal epithelium loss, hemorrhage, elevated mucus production and loss, altered mucus biochemistry, necrosis of skin tissue with loss of the protection against osmoregulatory and pathogens.
To evolve fish farming in an eco-efficient way, feed production must become less dependent on forage fish-based ingredients and make more use of low trophic level organisms, including microalgae, higher plants, as filter feeding organisms and other ingredients with low competition to established food value chains. Diets nearly free of fish meal and fish oil are not a novelty but are often composed of complex mixtures, containing supplements to meet the farmed animal’s nutritional requirements. Sustaining a growing aquaculture production, maintaining at the same time fish health, welfare, and profitability, and meeting strict environmental and food safety demands, is challenging and requires new technologies, great investments, and more knowledge. A benchmarking feeding trial was performed to demonstrate the main effects of four low trophic raw materials on Atlantic salmon ( Salmo salar ) growth, metabolism, skin health and fillet quality. To this end, a diet was produced to contain commercially relevant levels of fresh high quality organic FM and FO and was used as a control in the trial (FMFO). Heterotrophically produced Schizochytrium limacinum biomass was used to replace organic FO (HM diet). Spray dried cell wall disrupted biomass of the phototrophically cultured diatom Phaeodactylum tricornutum replaced partly FM and FO (PM diet). Black soldier fly ( Hermetia illucens ) larvae meal and tunicate ( Ciona intestinalis ) meal, were used to produce the diets BSFL and TM, respectively, replacing large parts of FM as compared to the FMFO. A fifth test diet was produced combining all test raw materials and removing all FM and FO (0FM0FO diet). All test ingredients were well accepted sustaining high growth rates (TGC values near 4) and feed efficiency (FCR values below 0.9) in salmon showing good gut health and normal metabolic responses. However, none of the treatments reached the growth performance of FMFO. Additional differences between test and control treatments were identified in dietary nutrient apparent digestibility, fish biometrics, blood metabolites and fillet and skin composition. Extensive raw material and dietary chemical characterisation was performed to provide insight on potential shortcomings in the novel low trophic level ingredients which can possibly be overcome combining complementary raw materials.
