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To assess the relationship among various measures of thermal tolerance and performance suggested for use in fish, we determined the critical thermal maximum (CTmax), critical swimming speed (Ucrit), maximum thermal tolerance while swimming [CTSmax] and realistic aerobic scope (ASR) of juvenile schoolmaster snapper (Lutjanus apodus). Their CTSmax (37.5±0.1°C) was only slightly lower than their CTmax (38.9±0.1°C) and this is probably because their maximum metabolic rate (MMR) and ASR during the former test were ∼42 and 65% higher, respectively. Furthermore, we did not observe a transition to unsteady (i.e. anaerobically fueled) swimming in the CTSmax test as we did in the Ucrit protocol. These data strongly suggest that thermal tolerance tests on fishes whose lifestyle involves schooling or sustained activity should be performed at ecologically relevant swimming speeds. Our results do not support the hypothesis that failure during a CTSmax test is due to a fish's inability to meet its tissue oxygen demands., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Stenothermal Antarctic notothenioid fishes are noteworthy for their history of isolation in extreme cold and their corresponding lack of the canonical heat shock response. Despite extensive transcriptomic studies, the mechanistic basis for stenothermy has not been fully elucidated. Given that the proteome better represents an organism's physiology, the possibility exists that some aspects of stenothermy arise posttranscriptionally. Here, Antarctic emerald rockcod ( Trematomus bernacchii ) were sampled after exposure to chronic and/or acute high temperatures, followed by a thorough assessment of proteomic responses in the brain, gill, and kidney. Few cellular stress response proteins were induced, and overall responses were modest in terms of the numbers of differentially expressed proteins and their fold changes. Inconsistencies in protein induction across treatments and tissues are suggestive of dysregulation, rather than an adaptive response. Changes in regulation of the translational machinery in Antarctic notothenioids could explain these patterns. Some components of translational regulatory pathways are highly conserved [e.g., Ser-52, eukaryotic translation initiation factor 2α (eIF2α)], but other proteins comprising the cellular "integrated stress response," specifically, the eIF2α kinases general control nonderepressible 2 (GCN2) and PKR-like endoplasmic reticulum kinase (PERK), may have evolved along different trajectories in Antarctic fishes. Taken together, these observations suggest a novel hypothesis for stenothermy and the absence of a coordinated cellular stress response in Antarctic fishes. NEW & NOTEWORTHY Antarctic fishes have some of the lowest known heat tolerances among vertebrates, but the molecular mechanisms underlying this pattern are not fully understood. By combining detailed analyses of protein expression patterns in several tissues under various heat treatments with a broader evolutionary perspective, this study offers a novel hypothesis to explain the narrow range of temperature tolerance in this extraordinary group of fishes.

Red drum, Sciaenops ocellatus, are a marine teleost native to the Gulf of Mexico that routinely experiences periods of low oxygen (hypoxia). Recent work has demonstrated this species has the capacity to improve aerobic performance in hypoxia through respiratory acclimation. However, it remains unknown how hypoxia acclimation impacts anaerobic metabolism in red drum, and the consequences of exhaustive exercise and recovery. Juvenile fish were acclimated to normoxia (n = 15, DO 90.4 ± 6.42 %) or hypoxia (n = 15, DO 33.6 ± 7.2 %) for 8 days then sampled at three time points: at rest, after exercise, and after a 3 h recovery period. The resting time point was used to characterize the acclimated phenotype, while the remaining time points demonstrate how this phenotype responds to exhaustive exercise. Whole blood, red muscle, white muscle, and heart tissues were sampled for metabolites and enzyme activity. The resting phenotype was characterized by lower pH e and changes to skeletal muscle ATP. Exhaustive exercise increased muscle lactate, and decreased phosphocreatine and ATP with no effect of acclimation. Interestingly, hypoxia-acclimated fish had higher pH e and pH i than control in all exercise time points. Red muscle ATP was lower in hypoxia-acclimated fish versus control at each sample period. Moreover, acclimated fish increased lactate dehydrogenase activity in the red muscle. Hypoxia acclimation increased white muscle ATP and hexokinase activity, a glycolytic enzyme. In a gait-transition swim test, hypoxia-acclimated fish recruited anaerobic-powered burst swimming at lower speeds in normoxia compared to control fish. These data suggest that acclimation increases reliance on anaerobic metabolism, and does not benefit recovery from exhaustive exercise., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The novel adipokine asprosin, produced by the furin enzymatic cleavage of profibrillin 1 protein (encoded by the Fbn1 gene), is implicated in regulating many physiological functions, including reproduction in mammals. In males, asprosin is reported to increase sperm density, sperm motility, and steroid production by interacting with Olfr734, which belongs to the G-protein-coupled receptor family (GPCR). In 2023, our group predicted and characterized asprosin in silico for the first time and demonstrated the robust expression of fbn1, and furin in the gonads of teleost spotted snakehead (ss) Channa punctata. Taking it forward, in the current study, we have investigated the effect of asprosin on the testicular functions of the spotted snakehead. As C. punctata is a seasonal breeder, the reproductive-phase-dependent expression of fbn1 in the testis was analyzed, showing significant upregulation during the preparatory and post-spawning phases. Additionally, bacterially overexpressed recombinant asprosin of C. punctata was purified to study the effect of ss asprosin on gametogenesis and steroidogenesis. Ex vivo treatment with recombinant asprosin resulted in significant upregulation of spermatogenic marker genes pcna, aldh1a2, cyp26a1, and sycp3. Asprosin also enhanced the gene expression of gonadotropin receptors, as well as sex steroid receptors, in addition to steroidogenic genes star and cyp17a1. Further exploring the downstream signaling cascade, the second messenger of GPCRs, cAMP levels following asprosin treatment were analyzed. Asprosin treatment prominently enhanced cAMP levels, thereby indicating the involvement of GPCR in the transduction of asprosin action. Hence, the study elucidates the regulation of male reproductive function by asprosin in spotted snakeheads.

The mandarin fish (Siniperca chuatsi), as a typical freshwater carnivorous fish, has high economic value. Mandarin fish have a peculiar feeding habit of feeding on other live fry during the first-feeding period, while rejecting zooplankton or particulate feed, which may be attributed to the low expression of zooplankton-associated gene sws1 in mandarin fish. The domesticated strain of mandarin fish could feed on Artemia at 3 days post hatching (dph). However, the mechanism of mandarin fish larvae recognize and forage Artemia as food is still unclear. In this study, we employed transcriptional analysis to identify the representative differential pathways between mandarin fish larvae unfed and fed with Artemia at 3 dph. The comparative transcriptome analysis has unveiled a tapestry of genetic expression, highlighting 403 genes that have been up-regulated and 259 that have been down-regulated, all of which constitute the differentially expressed genes (DEGs). KEGG pathway analysis revealed that the number of differentially expressed genes in the photoconductive signaling pathway was the largest. Next, the Vorinostat (suberoylanilide hydroxamic acid, SAHA) was used to assess whether sws1 induced ingestion of Artemia in mandarin fish larvae. We discovered that SAHA-treated larvae had more food intake of Artemia and up-regulated the transcription level of npy, which might have been associated with the up-regulated of sws1 opsin. Additionally, exposure to 0.5 µM SAHA increased the expression of genes involved in phototransduction pathway. These findings would provide insights on the molecular processes involved in mandarin fish larvae feeding on Artemia at the first-feeding stage., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The large yellow croaker ( Larimichthys crocea ) is an important economic fish in China. However, intensive farming practices, such as high stocking densities, suboptimal water quality, and imbalanced nutrition, have led to a decline in muscle quality. Muscle elasticity is a key texture property influencing muscle quality. Herein, transcriptomic and metabolomic analyses were performed on four groups: male high muscle elasticity (MEHM), female high muscle elasticity (MEHF), male low muscle elasticity (MELM), and female low muscle elasticity (MELF), to explore the molecular regulation underlying muscle elasticity in the large yellow croaker. Transcriptomics identified 2594 differentially expressed genes (DEGs) across the four groups, while metabolomics revealed 969 differentially expressed metabolites (DEMs). Association analysis indicated that the valine, leucine, and isoleucine biosynthesis pathways were significantly enriched between the MELF and MEHF groups; 2-Oxoisovalerate and L-Valine were DEMs; and the gene encoding L-threonine ammonia-lyase was a DEG. In the MELM and MEHM groups, pathways such as arginine biosynthesis; arginine and proline metabolism; and valine, leucine, and isoleucine degradation were significantly enriched. 4-guanidinobutanoate, L-aspartate, N-acetylornithine, and L-leucine were among the DEMs, while the DEGs included glul , gls , srm , hmgcs , and aacs . These findings provide insights into the molecular mechanisms controlling muscle elasticity, representing a theoretical foundation to breed high-quality large yellow croakers.

External and internal factors are involved in controlling the growth of fishes. However, little is known about the mechanisms by which external factors trigger stimulus signals. This study explored the physiological roles of melatonin in the transcription of growth-related genes in the brain and liver of Chrysiptera cyanea, a tropical damselfish with long-day preference. In brain samples of this species collected at 4-h intervals, the transcript levels of arylalkylamine N-acetyltransferase2 (aanat2), the rate-limiting enzyme of melatonin synthesis, and growth hormone (gh) peaked at 20:00 and 00:00, respectively. Concomitantly, the transcript levels of insulin-like growth factors (igf1 and igf2) in the brain and liver were upregulated during the scotophase. Levels of iodothyronine deiodinases (dio2 and dio3), enzymes that convert thyroxine (T4) to triiodothyronine (T3) and reverse T3, respectively, increased in the brain (dio2 and dio3) and liver (dio2) during the photophase, whereas dio3 levels in the liver showed the opposite trend. Fish reared in melatonin-containing water exhibited significant increases in the transcription levels of gh and igf1 in the brain and igf1 in the liver, suggesting that growth in this fish is positively regulated by the GH/IGF pathway on a daily basis. Melatonin treatment also stimulated the transcript levels of dio2 and dio3 in the liver, but not in the brain. Fish consuming pellets containing T3, but not T4, showed significant increases in gh and igf1 in the brain and igf1 and igf2 in the liver, suggesting that the intercellular actions of the TH/IGF pathway have an impact on growth on a daily basis. In summary, IGF synthesis and action in the brain and liver undergo dual regulation by distinct hormone networks, which may also be affected by daily, seasonal, or nutritional factors., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2023. Published by Elsevier Inc.)

Marine fishes excrete excess H + using basolateral Na + -K + -ATPase (NKA) and apical Na + /H + exchanger 3 (NHE3) in gill ionocytes. However, the mechanisms that regulate H + excretion during exposure to environmentally relevant hypercapnia (ERH) remain poorly understood. Here, we explored transcriptomic, proteomic, and cellular responses in gills of juvenile splitnose rockfish ( Sebastes diploproa ) exposed to 3 days of ERH conditions (pH ∼7.5, ∼1,600 μatm Pco 2 ). Blood pH was fully regulated at ∼7.75 despite a lack of significant changes in gill 1 ) mRNAs coding for proteins involved in blood acid-base regulation, 2 ) total NKA and NHE3 protein abundance, and 3 ) ionocyte density. However, ERH-exposed rockfish demonstrated increased NKA and NHE3 abundance on the ionocyte plasma membrane coupled with wider apical membranes and greater extension of apical microvilli. The observed gill ionocyte remodeling is consistent with enhanced H + excretion that maintains blood pH homeostasis during exposure to ERH and does not necessitate changes at the expression or translation levels. These mechanisms of phenotypic plasticity may allow fishes to regulate blood pH during environmentally relevant acid-base challenges and thus have important implications for both understanding how organisms respond to climate change and for selecting appropriate metrics to evaluate its impact on marine ecosystems. NEW & NOTEWORTHY Splitnose rockfish exposed to environmentally relevant hypercapnia utilize existing proteins (rather than generate additional machinery) to maintain homeostasis.

Fatty acid-binding protein 1 (FABP1) plays an important role in regulating fatty acid metabolism in liver, which is a potential therapeutic target for diseases such as non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms are not well defined. Using complementary experimental models, we discovered FABP1 induction in hepatocytes as a primary mediator of lipogenesis when exposed to fatty acids, especially saturated fatty acids (SFAs). In the feeding trial, palm oil led to excess lipid accumulation in the liver of large yellow croaker (Larimichthys crocea), accompanied by significant induction of FABP1. In cultured cells, palmitic acid (PA), a kind of SFA, triggered the fabp1 expression and increased triglyceride (TG) contents. Knockdown of FABP1 dampened PA-induced TG accumulation through mitigated lipogenesis. The overexpression of FABP1 showed the opposite result. Furthermore, the inactivation of FABP1 led to induction in insulin-induced gene 1 (INSIG1) expression, which attenuated the processing of sterol regulatory element-binding protein 1 (SREBP1) by down-regulating the nuclear-localized SREBP1. These results revealed a previously unrecognized function of FABP1 in response to PA, providing additional evidence for targeting FABP1 in the treatment of NAFLD caused by SFA., (© 2024 Federation of American Societies for Experimental Biology.)

Metabotropic glutamate receptor 4 (mGluR4) is widely regarded as an umami receptor activated by L-glutamate to exert essential functions. Numerous studies have shown that umami receptors participate in food intake regulation. However, little is known about mGluR4's role in mediating food ingestion and its possible molecular mechanism. Mandarin fish, a typical carnivorous fish, is sensitive to umami substances and is a promising vertebrate model organism for studying the umami receptor. In this study, we identified the mGluR4 gene and conducted evolutionary analyses from diverse fish species with different feeding habits. mGluR4 of mandarin fish was cloned and functionally expressed to investigate the effects of L-glutamate on mGluR4. We further explored whether the signal pathway mGluR4-Ca 2+ -ERK1/2 participates in the process in mandarin fish brain cells. The results suggest that L-glutamate could regulate Neuropeptide Y (Npy) via the mGluR4-Ca 2+ -ERK1/2 signaling pathway in mandarin fish. Our findings unveil the role of mGluR4 in feeding decisions and its possible molecular mechanisms in carnivorous fishes.

Background/Objectives : Stearoyl-coenzyme A desaturase 1 (SCD1) plays a crucial role in fatty acid metabolism. However, its roles in the feeding habit transformation of mandarin fish ( Siniperca chuatsi ) remain largely unknown. Methods: Juvenile mandarin fish (10.37 ± 0.54)g were trained to feed on an artificial diet and then divided into artificial diet feeders and nonfeeders according to their feed preference. Afterwards, the scd1 gene of mandarin fish ( Sc-scd1 ) was identified and characterized, and its transcription difference was determined between S. chuatsi fed live artificial diets and those fed prey fish. Results: Our results show that Sc-scd1 coding sequence is 1002 bp long, encoding 333 amino acids. The assumed Sc -SCD1 protein lacks a signal peptide, and it contains 1 N-linked glycosylation site, 24 phosphorylation sites, 4 transmembrane structures, and 3 conserved histidine elements. We found that Sc -SCD1 exhibits a high similarity with its counterparts in other fish by multiple alignments and phylogenetic analysis. The expression level of Sc-scd1 was detected with different expression levels in all tested tissues between male and female individuals fed either live prey fish or artificial diets. Conclusions: In particular, the Sc-scd1 expression level was the highest in the liver of both male and female mandarin fish fed artificial diets, indicating that scd1 genes may be associated with feed adaption of mandarin fish. Taken together, our findings offer novel perspectives on the potential roles of scd1 in specific domestication, and they provide valuable genetic information on feeding habits for the domestication of mandarin fish.

Background: Temperature is a crucial environmental determinant for the vitality and development of teleost fish, yet the underlying mechanisms by which they sense temperature fluctuations remain largely unexplored. Transient receptor potential (TRP) proteins, renowned for their involvement in temperature sensing, have not been characterized in teleost fish, especially regarding their temperature-sensing capabilities., Results: In this study, a genome-wide analysis was conducted, identifying a total of 28 TRP genes in the mandarin fish Siniperca chuatsi. These genes were categorized into the families of TRPA, TRPC, TRPP, TRPM, TRPML, and TRPV. Despite notable variations in conserved motifs across different subfamilies, TRP family members shared common structural features, including ankyrin repeats and the TRP domain. Tissue expression analysis showed that each of these TRP genes exhibited a unique expression pattern. Furthermore, examination of the tissue expression patterns of ten selected TRP genes following exposure to both high and low temperature stress indicated the expression of TRP genes were responsive to temperatures changes. Moreover, the expression profiles of TRP genes in response to mandarin fish virus infections showed significant upregulation for most genes after Siniperca chuatsi rhabdovirus, mandarin fish iridovirus and infectious spleen and kidney necrosis virus infection., Conclusions: This study characterized the TRP family genes in mandarin fish genome-wide, and explored their expression patterns in response to temperature stress and virus infections. Our work will enhance the overall understanding of fish TRP channels and their possible functions., (© 2024. The Author(s).)

The affect of temperature on tissue protein synthesis rates has been reported in temperate and tropical, but not Antarctic fishes. Previous studies have generally demonstrated low growth rates in Antarctic fish species in comparison to temperate relatives and elevated levels of protein turnover. This study investigates how low temperatures effect tissue protein synthesis and hence tissue growth in a polar fish species. Groups of Antarctic, Harpagifer antarcticus and temperate, Lipophrys pholis, were acclimated to a range of overlapping water temperatures and protein synthesis was measure in white muscle (WM), liver and gastrointestinal tract (GIT). WM protein synthesis rates increased linearly with temperature in both species (H. antarcticus 0.16-0.23%.d -1 , L. pholis, 0.31-0.76%.d -1 ), while liver (H. antarcticus 0.24-0.27%.d -1 , L. pholis, 0.44-1.03%.d -1 ) and GIT were unaffected by temperature in H. antarcticus but increased non-linearly in L.pholis (H. antarcticus 0.22-0.26%.d -1 , L. pholis, 0.40-0.86%.d -1 ). RNA to protein ratios were unaffected by temperature in H. antarcticus but increased weakly, in L.pholis WM and liver. In L.pholis, RNA translational efficiency increased significantly with temperature in all tissues, but only in liver in H. antarcticus. At the overlapping temperature of 3 °C, protein synthesis (WM 26%, Liver, 39%, GIT, 35%) and RNA translational efficiency (WM 273%, Liver, 271%, GIT, 300%) were significantly lower in H. antarcticus than L.pholis, while RNA to protein ratios were significantly higher (WM 270%, Liver 170%, GIT 186%). Tissue specific effects of temperature are detectable in both species. This study provides the first evidence, that tissue protein synthesis rates are constrained in Antarctic fishes., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Regional endothermy is the ability of an animal to elevate the temperature of specific regions of the body above that of the surrounding environment and has evolved independently among several fish lineages. Sarcolipin (SLN) is a small transmembrane protein that uncouples the sarcoplasmic reticulum calcium ATPase pump (SERCA1b) resulting in futile Ca 2+ cycling and is thought to play a role in non-shivering thermogenesis (NST) in cold-challenged mammals and possibly some fishes. This study investigated the relative expression of sln and serca1 transcripts in three regionally-endothermic fishes (the skipjack, Katsuwonus pelamis, and yellowfin tuna, Thunnus albacares, both of which elevate the temperatures of their slow-twitch red skeletal muscle (RM) and extraocular muscles (EM), as well as the cranial endothermic swordfish, Xiphias gladius), and closely related ectothermic scombrids (the Eastern Pacific bonito, Sarda chiliensis, and Pacific chub mackerel, Scomber japonicus). Using Reverse Transcription quantitative PCR (RT-qPCR) and species-specific primers, relative sln expression trended higher in both the RM and EM for all four scombrid species compared to white muscle. In addition, relative serca1 expression was found to be higher in RM of skipjack and yellowfin tuna in comparison to white muscle. However, neither sln nor serca1 transcripts were higher in swordfish RM, EM or cranial heater tissue in comparison to white muscle. A key phosphorylation site in sarcolipin, threonine 5, is conserved in the swordfish, but is mutated to alanine or valine in tunas and the endothermic smalleye Pacific opah, Lampris incognitus, which should result in increased uncoupling of the SERCA pump. Our results support the role of potential SLN-NST in endothermic tunas and the lack thereof for swordfish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Dietary kelp possesses a variety of useful biological qualities but does not have a toxic effect on the host. In this study, we examine how kelp dietary supplementation enhances the serum biochemistry, intestinal immunity, and metabolism of hybrid snakehead. A total of 810 juvenile hybrid snakeheads (Channa maculata ♀ × Channa argus ♂), with an initial average weight of 11.4 ± 0.15 g, were allocated randomly to three treatment groups (three replicates per group). The fish were fed for 60 days with isonitrogenous and isolipidic diets. The groups were the control group (C) (20% high-gluten flour), the medium replacement group (MR) (10% high-gluten flour and 10% kelp meal), and the full replacement group (FR) (0% high-gluten flour and 15% kelp meal)., Results: The results showed that dietary kelp increased the activity of serum antioxidant enzymes significantly and decreased the content of serum malondialdehyde (MDA) in hybrid snakeheads, with significant changes in the FR group (P < 0.05). The intestinal morphology results showed that dietary kelp helped to increase the specific surface area of intestinal villi, which was beneficial for intestinal digestion and absorption. According to transcriptome and quantitative real-time polymerase chain reaction (qRT-PCR) analysis, dietary kelp can improve the expression of intestinal immunity and metabolism-related pathways. Among them, immune-related genes MHC1 and HSPA1 were significantly up-regulated, and IGH, MHC2, and IL-8 were significantly down-regulated (P < 0.05). Lipid metabolism-related genes DGAT2, FABP2, RXRα, and PLPP1 were all significantly up-regulated (P < 0.05)., Conclusion: Dietary kelp can effectively improve the antioxidant function of hybrid snakeheads, improve intestinal morphology, reduce intestinal inflammation, and promote intestinal lipid synthesis and transportation, thereby improving intestinal immunity and metabolic functions. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

A tandem mass tagging-labeled proteomic approach was employed to explore the relationship between quality parameters and protein changes in large yellow croaker fillets refrigerated under carbon dioxide, oxygen, and nitrogen atmospheres. After 96 h, fillets stored in carbon dioxide and nitrogen showed improved texture, water-holding capacity, and color, compared to those stored in oxygen. Functional analysis respectively identified 117 and 65 differentially expressed proteins in carbon dioxide and nitrogen, including key proteins such as troponin, myosin light chain, actin, and collagen types IV and XIII, that were linked to extracellular adhesion, cytoskeleton integrity, energy metabolism, and membrane functions. Carbon dioxide and nitrogen were detrimental to the growth and reproduction of aerobic microorganisms. High concentrations of carbon dioxide can inhibit microbial activity, while nitrogen preserves freshness by regulating the pressure balance within the packaging. These findings provided a theoretical basis for the optimized gas-conditioned preservation of large yellow croaker fillets., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, we explored the correlation between the lysosome-mitochondrial apoptosis pathway and fish softening, as well as the correlation between ferritin degradation and lysosomal iron changes. The results indicated that ferritin levels gradually decreased, lysosomal iron first increased and then decreased and tended to stabilize, and lysosomal membrane stability significantly decreased (p < 0.05). Spearman's analysis suggested that an increase in lysosomal iron was associated with ferritin degradation. Lysosomal instability promoted the release of cathepsin D, thereby increasing the release of Bid and Bax, and inhibiting the expression of Bcl-2. Subsequently, caspase-9/-3 was activated. In addition, transmission electron microscopy revealed ultrastructural damage to mitochondria and cell nuclei, which are morphological features of apoptosis during post-mortem storage. Moreover, TUNEL staining confirmed the occurrence of apoptosis. We concluded that the lysosome- mitochondrial apoptosis pathway was active during the storage of Esox Lucius, in which ferritin degradation and increased lysosomal iron were key factors inducing lysosomal damage, and cathepsin D released by lysosomes was a key factor connecting lysosomes and mitochondria., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that might influence the work described herein., (Copyright © 2024. Published by Elsevier Ltd.)

Large yellow croaker (Larimichthys crocea) is susceptible to oxidative denaturation during storage. This work is to investigate the quality alterations by analyzing its physicochemical changes and proteomics throughout preservation under refrigeration, frozen, and slurry ice (SI) conditions. Results revealed that the freshness of large yellow croaker, as evaluated by indicators such as total volatile basic nitrogen, total viable count, and thiobarbituric acid reactive substances, was well maintained while stored in the SI group. Meanwhile, the water distribution in the muscle tissue of group SI exhibited slower fluctuations, thereby preserving the integrity of fish muscle cells. Based on label-free proteomic analysis, a considerable downregulation was observed in the mitogen-activated protein kinase (MAPK) signaling pathway, indicating that SI decelerated this metabolic pathway and effectively delayed the deterioration of muscle. Therefore, the application of SI provides potential for maintaining the quality stability of large yellow croaker., Competing Interests: Declaration of competing interest The authors declare that they do not possess any recognized competing financial interests or personal relationships that could have potentially influenced the findings presented in this research., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Microplastic pollution is a growing environmental issue, even reaching remote areas like the Arctic and Antarctic, posing threats to biodiversity and food chains. The present research represents a pioneering endeavor aimed at exploring the relationship between lipids and microplastics in 20 wild specimens of Trematomus bernacchii from the Ross Sea (Antarctica). Fish were grouped in MPs-ingested and MPs-free based on whether they had ingested microplastics. Raman spectroscopy revealed that contaminated fish samples contained from one to three different types of polymeric fibers (1.4 items/specimen, ± = 0.7), specifically, polyester (PES), polypropylene (PP), and polyethylene terephthalate (PET). Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) techniques were employed for the study of the lipid composition in term of fatty acids methyl esters (FAMEs). Fifty different FAME compounds were identified and quantified in the lipid fraction extracted from the muscle tissues of the selected fish samples. Polyunsaturated fatty acids (PUFAs) are the most abundant family of fatty acids in T. bernacchii species with eicosapentaenoic (C20:5ω3) and docosahexaenoic (C22:6ω3) acids as main components. In detail, PUFA class accounted for 46.78 ± 6.82% and 44.62 ± 4.86% of the total fatty acid composition in MPs-ingested and MPs-free groups, respectively. The contents of the monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs) varied from 27.93% to 31.15% and from 24.23% to 25.05% in MPs-ingested and MPs-free fish samples, respectively. Based on Mann-Whitney test results (p < 0.05), there was no significant difference from a statistical point of view between two groups of fishes. Additionally, nutritional quality indices exhibited comparable values between groups. Results showed that no significant differences were found in the fatty acids distribution between the two groups. This indicates that the lipid composition of wild fish that are naturally exposed to plastic pollution remains unchanged and could still have beneficial effects on human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Spexin (SPX1) is a novel neuropeptide composed of 14 amino acids and well conserved across vertebrates, and it has been implicated in various physiological functions via galanin receptor 2 (GALR2) and GALR3. However, the detailed signaling pathways mediating its actions in target cells are still largely unknown. Accordingly, we addressed this issue in the present study using yellowtail kingfish as a model. SPX1 significantly increased CRE-luc activity in COS-7 cells expressing its cognate receptors GALR2a and GALR2b, and this stimulatory effect was attenuated by two inhibitors of the PKA pathway. Similarly, an evident induction of SRE-luc activity was observed when COS-7 cells transfected with GALR1b, GALR2a, GALR2b, GALR type 1, or GALR type 2 were challenged with SPX1, and two blockers of the PKC pathway suppressed this stimulatory action. Moreover, SPX1 markedly elevated NFAT-RE-luc activity in COS-7 cells expressing GALR1a, GALR2a, or GALR2b, and this promotion was inhibited by two antagonists of the Ca 2+ route. Overall, our results have revealed that activation of six yellowtail kingfish galanin receptors by the SPX1 peptide may occur with different downstream signaling events, which could account for its pleotropic functions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Spexin (SPX1) is a neuropeptide of 14 amino acids (aa), originally identified by bioinformatics, which has been implicated in various physiological functions in vertebrates via galanin receptors 2 and 3 (GALR2/3). To clarify the biological role of SPX1 in the control of reproduction in yellowtail kingfish, which is regarded as a promising species for offshore aquaculture worldwide, cDNA sequences of spx1 and six potential receptors were identified in the current study. The open reading frame of yellowtail kingfish spx1 was 363 nucleotides in size that encoded a 120-aa preprohormone, and its mature peptide was highly conserved among other species. The cDNA sequences of six GALRs (galr1a, galr1b, galr2a, galr2b, galr type 1, and galr type 2) were 1053 base pairs (bp), 1068 bp, 981 bp, 1137 bp, 1038 bp, 924 bp, which encoded G protein-coupled receptors of 350 aa, 355 aa, 326 aa, 378 aa, 345 aa, 307 aa, respectively. Tissue distribution analysis showed that spx1, galr1b, and galr2b transcripts were mainly detected in the brain. The highest mRNA levels of galr1a and galr2a were observed in the pituitary, followed by the brain and ovary. Both galr type 1 and galr type 2 were widely expressed in various tissues, with a peak level in the kidney. Moreover, all spx1 and galr genes significantly fluctuated during early ontogeny, exhibiting different expression patterns. Intraperitoneal injection of SPX1 significantly increased brain gnrh1, gnih, spx1, gal, and tac3 expression, while it inhibited gnrh2, kiss1r, and kiss2r mRNA levels. In the pituitary, SPX1 injection reduced transcript levels of gh, lhβ, and fshβ. Overall, our results have revealed the involvement of SPX1 in the reproductive functions in yellowtail kingfish., Competing Interests: Declarations Ethics approval All of the animal experiments were approved by the Institutional Animal Care and Use Committee, YSFRI, CAFS. Competing interests The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Mandarin fish (Siniperca chuatsi) is an important cultured fish in East Asia that shows sexual size dimorphism (SSD), with females growing faster than males when reaching marketable size. However, the regulatory mechanism of SSD is not clear. To characterize SSD of mandarin fish and its association with gh/igf1/igfbp-5 expression, gonadal developmental atlas of the females and the males were described, and growth parameters and serum levels of E2 and T, as well as the relative expression levels of gh, igf1, and igfbp-5a/b mRNAs, were determined. The results showed that the logistic growth equation of body mass and total length of female and male were W(♀) = 667.57/(1 + e^(4.19 - 1.24*t)), W(♂) = 582.71/(1 + e^(4.07 - 1.27*t)), L(♀) = 31.47/(1 + e^1.95 - 1.08*t)), L(♂) = 26.20/(1 + e^(2.56 - 1.5*t)). The month of inflection points for body mass for females and males were 3.37 mph and 3.20 mph, respectively, when the body mass were 333.79 g and 291.36 g. The month of inflection points for total length growth were 1.80 mph and 1.70 mph, respectively, when the total length were 18.52 cm and 16.28 cm. At 1.5-2.0 mph, SSD was not clearly demonstrated. At 3.0 mph, the body mass of the females was significantly higher than that of the males (P < 0.05), Serum E2, brain gh, and liver igf1 expression of the females was significantly higher than that of the males (P < 0.05); T content of the males was significantly higher than that of the females (P < 0.05). At 4.0 months of age, the body mass of the females was highly significantly higher than that of the males (P < 0.01), Serum E2, brain gh, and liver igf1 expression of the females was highly significantly higher than that of the males (P < 0.05); T content of the males was significantly higher than that of the females (P < 0.05). With the continuous development of gonads, muscle and liver igfbp-5a and -5b expression generally tend to increase in females and males, while igfbp-5a showed a gradual increasing trend, and igfbp-5b expression showed a trend of decreasing and then increasing. Male igfbp-5a/b expression was significantly higher than female at the age of 3.0-4.0 months (P < 0.05). This work verified that the females had faster growth rate since 3.0 mph compared to the males, which may be related to higher E2 levels in females leading to higher igf1 level, through inhibition of igfbp-5a/b expression., Competing Interests: Declarations Ethics approval All research involving animals was conducted according to the approved protocols of the animal ethics committee of Shanghai Ocean University. Conflict of interest The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Protein hydrolysates derived from aquaculture by-products hold significant promise as key components in the formulation of active films. In our study, we investigated the impact of different protein hydrolysates levels (0.4%, 0.8%, and 1.2%) obtained from the cutting by-product of Serra Spanish mackerel on the mechanical (PHSSM), morphological, optical, thermal, and antioxidant properties, as well as the degradability of biodegradable films. Four treatments were produced, varying the concentrations of PHSSM: C (control, without PHSSM), T4 (with 0.4% PHSSM), T8 (with 0.8% PHSSM), and T12 (with 1.2% PHSSM). These films were based on myofibrillar proteins from fish by-products and pectin extracted from yellow passion fruit. The incorporation of PHSSM led to enhanced barrier properties, resulting in a proportional reduction in water vapor permeability compared to the control film. However, high PHSSM levels (>0.8%) compromised film homogeneity and increased fracture susceptibility. Tensile strength remained unaffected (p > 0.05). PHSSM-enriched films exhibited reduced transparency and lightness, regardless of PHSSM concentration. The addition of PHSSM imparted a darker, reddish-yellow hue to the films, indicative of heightened visible light barrier properties. Moreover, increased PHSSM content (0.8% and 1.2%) appeared to accelerate film degradation in soil. Fourier transform infrared spectroscopy confirmed the presence of pectin-protein complexes in the films, with no discernible differences among the treated samples in the spectra. Incorporating PHSSM also enhanced film crystallinity and thermal resistance. Furthermore, an improvement in the antioxidant activity of the films was observed with PHSSM addition, dependent on concentration. The T8 emerged as the promising candidate for developing active primary packaging suitable for oxidation-sensitive foods., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The purpose of this study was to determine the effect of pre-rigor salting on the quality characteristics of surimi gels prepared from snakehead fish muscle. Pre-rigor and post-rigor muscle were mixed with 0.3% or 3% NaCl (w/w) and made into surimi gels, respectively. Results showed that pre-rigor muscle had a higher content of ATP, longer sarcomere, higher pH and greater protein solubility. Metabolic profile suggested that pre-rigor muscle had higher content (a 28-fold increase) of antioxidants such as butyryl-l-carnitine. Transmission electron microscopy showed more damage of mitochondria in post-rigor muscle. Surimi paste from pre-rigor meat chopped with 3% NaCl generally showed greater radical scavenging ability and had higher content of free sulfhydryl. Surimi gel made from pre-rigor muscle salted with 3% NaCl showed a larger gel strength (3.18 kg*mm vs. 2.22 kg*mm) and better water-holding (86% vs. 80%) than that of post-rigor group. Based on these findings, we hypothesized that: In addition to other factors such as pH, degree of denaturation, etc., less protein oxidation in pre-rigor salted surimi also contributes to the improved gel properties., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Cured Spanish mackerel has a promising market owing to its nutritious nature as well as ease of transportation and preservation. However, the nutritional and flavor formation mechanism of Spanish mackerel after curing and drying is unclear. To overcome this problem, the effects of different processing conditions on the free amino acid, microbial community, and flavor of Spanish mackerel were explored. Staphylococcus and Cobetia are the main microorganisms in cured mackerel and are closely associated with the formation of their quality. Compared with fresh mackerel, cured mackerel contains increased levels of protein, fat, and chloride, contributing to its distinctive flavor. The contents of free amino acids in the BA64 group were substantially higher than those in other groups, particularly the contents of threonine, glycine, and tyrosine. These findings will contribute to the development of high-quality cured Spanish mackerel products and cured aquatic products., Competing Interests: Declaration of competing interest None, (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Leptins and other related genes have been proven to play vital roles in food intake, weight control, and other life activities. While the function of leptins in yellowtail kingfish (Seriola lalandi) has not yet been explored, in the present study, we investigated the structure and preliminary function of four leptin-related genes in S. lalandi. In detail, the sequence of two leptin genes (lepa and lepb), one leptin receptor gene (lepr), and one leptin receptor overlapping transcript (leprot) gene were obtained by homology cloning and RACE methods, in which lepa and lepb have similar structure. Moreover, homologous sequence alignment and evolutionary analysis of all four genes were clustered with Seriola dumerili. The tissue distribution of these four genes in thirteen tissues of yellowtail kingfish was detected by RT-qPCR. Both lepa and leprot were highly expressed in the brain and ovary, while lepb was highly expressed in the pituitary, gill, muscle, and ovary; lepr was highly expressed in the gill, kidney, and ovary. Additionally, these four genes also played roles in embryo development and early growth and development of larvae and juveniles of yellowtail kingfish. Finally, the function of leptin and leptin-related genes was investigated during fasting and re-feeding adaption of yellowtail kingfish. The results showed that these four genes have different regulation functions in five tissues; for example, the mRNA levels of lepa, lepr, and leprot in the brain decreased during fasting and immediately increased after re-feeding, while the mRNA level of lepb did not show significant fluctuation during starvation but significantly lowered after re-feeding. However, lepa and lepb mRNA levels were significantly elevated during fasting and returned to control levels after re-feeding, and there were no significant changes in the expression of lepr and leprot in the liver during fasting and after re-feeding. Moreover, the body mass of fish in the experimental group was measured, and compensatory growth was found after the resumption of feeding. These results suggested that leptin and receptor genes play different functions in different tissues to regulate the physiological state of fish in food deficiency and gain processes., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Scope: This study investigates the impact of extracts derived from Antarctic fish species, Trematomus newnesi and Trematomus bernacchii, on the migration of human placental trophoblast JEG-3 cells, which is a crucial aspect of successful pregnancy., Methods and Results: The extracts, obtained from the muscles of these fish, significantly enhance the migration and invasion of JEG-3 cells in in vitro wound healing, Transwell, and collagen invasion assays. These effects are accompanied by an increase in matrix metalloproteinase (MMP) 9 activity, as demonstrated by zymography. Furthermore, the extracts activated Akt and protein phosphatase 1, resulting in the dephosphorylation of β-catenin at Ser33/37/Thr41, as confirmed by western blot analysis. Consequently, MMP9 is upregulated, while metallopeptidase inhibitor 1/3 is downregulated, as verified by western blot and qRT-PCR analyses. Finally, utilizing ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis, followed by matching with the Global Natural Product Social Molecular Networking library, the study annotates the compound responsible for the observed migratory activity as taurocholic acid. Importantly, the study confirms that taurocholic acid enhances cell migration in JEG-3 cells., Conclusion: The results of this study emphasize the potential of Antarctic fish extracts in promoting extravillous trophoblast migration and invasion, which are critical for successful pregnancy., (© 2024 The Author(s). Molecular Nutrition & Food Research published by Wiley‐VCH GmbH.)

A large number of studies on organophosphate esters (tri-OPEs) in marine organisms have not assessed the simultaneous occurrence of tri-OPEs and their metabolites (di-OPEs) in these species. This research investigated the concentration and geographical distribution of 15 tri-OPEs and 7 di-OPEs in 172 samples of Pampus argenteus that were collected annually from 2021 to 2023 at three distinct locations along the Vietnamese coast. As a result, tri-OPEs and di-OPEs were detected in numerous fish samples, indicating their widespread spatial and temporal occurrence in marine fish and pointing out the importance of monitoring their levels. The tri-OPEs and di-OPEs ranged within 2.1-38.9 ng g -1 dry weight (dw) and 3.2-263.4 ng g -1 dw, respectively. The mean concentrations of tri-OPEs ranged from 0.4 (TIPrP) to 5.4 ng g -1 dw (TBOEP), with TBOEP and TEHP having the highest mean values. In addition, the profiles of tri-OPEs in fish exhibited a descending order: Σalkyl OPEs > ΣCl-alkyl OPEs > Σaryl OPEs. The di-OPEs, namely BEHP and DMP, had the highest mean levels, measuring 33.4 ng g -1 dw and 23.8 ng g -1 dw, respectively. Furthermore, there have been significant findings of strong positive correlations between di-OPEs and tri-OPE pairs (p < 0.05). It is worth noting that there is a noticeable difference in the composition of tri-OPEs between the North and other regions. Despite these findings, the presence of OPE-contaminated fish did not pose any health risks to Vietnam's coastal population., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Insulin-like growth factor-binding proteins (IGFBPs) play important roles in regulating growth and development by binding to IGF, where IGFBP-3 and IGFBP-5 are the main binding carriers of IGF in the circulation system. In the present study, the gene sequences of igfbp-3, igfbp-5a, and igfbp-5b were cloned from the liver of yellowtail kingfish (Seriola lalandi). The ORF sequences of igfbp-3, igfbp-5a, and igfbp-5b were 888, 801, and 804 bp in length, which encoded 295, 266, and 267 amino acids, respectively. The above three genes were widely expressed in yellowtail kingfish tissues, with igfbp-3 being the most highly expressed in the heart, brain, and gonads, while igfbp-5a and igfbp-5b were both most highly expressed in the liver and kidney. The expression levels of igfbp-3, igfbp-5a, and igfbp-5b were detected throughout the embryonic and larval stages, suggesting their roles in early development and growth regulation of yellowtail kingfish. Besides, igfbp-3 and igfbp-5a were significantly up-regulated in the liver under food deprivation and high-density rearing conditions, which was exactly opposite to the growth performance of yellowtail kingfish, implying that they may serve as biomarkers of adverse culture conditions. Overall, the above results initially identified the molecular characteristics of igfbp-3/-5a/-5b in yellowtail kingfish and implied that they might play important roles in the growth and development, providing a basis for further research on underlying regulatory mechanisms., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Fishmeal is over-represented in the diets of large yellow croaker (Larimichthys crocea), and this farming mode, which relies heavily on fishmeal, is highly susceptible to the price of fishmeal and is unsustainable. Therefore, more and more studies on the large yellow croaker tend to replace fishmeal with land-based animal or plant proteins, but few studies have considered it from the genomic selection. In this study, we evaluated the survival rate (SR), final body weight (FBW), body weight gain (BWG), weight gain rate (WGR), and specific growth rate (SGR) of the large yellow croaker GS7 strain, which was obtained through genomic selection for tolerance to plant proteins and analyzed the differences in plant protein utilization between the GS7 strain and unselected commercial large yellow croaker (control group). The results of separate feeding for 60 days showed that although there was no significant difference in SR between the control and GS7 strains (P > 0.05), the BWG, WGR, and SGR of the control were significantly lower (P < 0.05) than those of the GS7 group. Results of mixed feeding after PIT marking showed that compared to the control fish, the GS7 strain had significantly higher BWG, WGR, and SGR (P < 0.0001). To make the experimental results more precise, we compared fishes with equivalent initial body weight (IBW) in the GS7 strain and the control group. The final fish body weight (FBW) of Ctrl-2 (IBW 300-399 g) and Ctrl-4 (IBW 500-599 g) was significantly lower than those of the corresponding GS7-2 and GS7-4 (P < 0.05), while the FBW of Ctrl-1 (IBW 200-299 g) and Ctrl-3 (IBW 400-499 g) was much significantly lower than the corresponding GS7-1 and GS7-3 (P < 0.01). The BWG, WGR, and SGR of Ctrl-1 and Ctrl-4 were more significantly lower than those of the corresponding GS7-1 and GS7-4 (P < 0.01), while the BWG, WGR, and SGR of Ctrl-2 and Ctrl-3 were more significantly different from the corresponding GS7-2 and GS7-3 (P < 0.0001). Our results seem to point toward the same conclusion that the GS7 strain is better adapted to high plant protein diets than the unselected commercial large yellow croaker. These results will provide a reference for the low-fishmeal culture industry of large yellow croakers and the selection and breeding of strains tolerant to a high percentage of plant proteins in other marine fishes., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Antimicrobial peptides (AMPs) are an important component of innate immunity in both vertebrates and invertebrates, and some of the unique characteristics of AMPs are usually associated with their living environment. The marine fish, mudskipper Boleophthalmus pectinirostris, usually live amphibiously in intertidal environments that are quite different from other fish species, which would be an exceptional source of new AMPs. In the study, an AMP named Bolespleenin 334-347 was identified, which was a truncated peptide derived from a new functional gene found in B. pectinirostris, that was up-regulated in response to bacterial challenge. Bolespleenin 334-347 had only 14 amino acid residues, including five consecutive arginine residues. It was found that the peptide had broad-spectrum antibacterial activity, good thermal stability and sodium ion tolerance. Bolespleenin 334-347 killed Acinetobacter baumannii and Staphylococcus aureus by disrupting the structural integrity of the bacterial membrane, leading to leakage of the cellular contents, and inducing accumulation of bacterial endogenous reactive oxygen species (ROS). In addition, Bolespleenin 334-347 effectively inhibited biofilm formation of A. baumannii and S. aureus and long-term treatment did not lead to the development of resistance. Importantly, Bolespleenin 334-347 maintained stable activity against clinically multi-drug resistant bacterial strains. In addition, it was noteworthy that Bolespleenin 334-347 showed superior efficacy to LL-37 and vancomycin in a constructed mouse model of MRSA-induced superficial skin infections, as evidenced by a significant reduction in bacterial load and more favorable wound healing. This study provides an effective antimicrobial agent for topical skin infections with potential therapeutic efficacy for infections with drug-resistant bacteria, including MRSA., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

TGF-β1/Smads is a classic signaling pathway, which plays important roles in the development process of organisms. Black porgy Acanthopagrus schlegelii and red porgy Pagrus major are valuable economic fishes, and their hybrid offspring show excellent heterosis traits. Yet the molecular regulation mechanism of the heterosis traits is less clear. Here, we explored the TGF-β1/Smads pathway's molecular genetic information for heterosis in A. schlegelii ♂ × P. major ♀ (AP) and A. schlegelii ♀ × P. major ♂ (PA) in terms of growth and development. The mRNA expression levels of TGF-β1 , TβR-I , TβR-II , and Smad2 genes in different developmental stages of A. schlegelii were detected. Furthermore, the expression levels of TGF-β1 , TβR-I , TβR-II , and Smad2 genes in different tissues of adult (mRNA level) and larva (mRNA and protein level) of A. schlegelii , P. major , and their hybrids were determined by both real-time quantitative PCR and Western blot techniques. The results indicated the ubiquitous expression of these genes in all developmental stages of A. schlegelii and in all tested tissues of A. schlegelii , P. major, and its hybrids. Among them, the mRNA of TGF-β1 , TβR-I, and TβR-II genes is highly expressed in the liver, gill, kidney, and muscle of black porgy, red porgy, and their hybrid offspring. There are significant changes in gene and protein expression levels in hybrid offspring, which indirectly reflect hybrid advantage. In addition, there was no correlation between protein and mRNA expression levels of Smad2 protein. The results provide novel data for the differential expression of growth and development genes between the reciprocal hybridization generation of black porgy and red porgy and its parents, which is conducive to further explaining the molecular regulation mechanism of heterosis in the growth and development of hybrid porgy.

The present research focuses on the seasonal changes in the energy content and metabolic patterns of red porgy (Pagrus pagrus) sampled in a fish farm in North Evoikos Gulf (Greece). The study was designed in an effort to evaluate the influence of seasonality in several physiological feauteres of high commercial importance that may affect feed intake and growth. We determined glycogen, lipids and proteins levels, and cellular energy allocation (CEA) as a valuable marker of exposure to stress, which integrates available energy (Ea) and energy consumption (Ec). Metabolic patterns and aerobic oxidation potential were based on the determination of glucose transporter (GLU), carnitine transporter (CTP), L-lactate dehydrogenase (L-LDH), citrate synthase (CS), cytochrome C oxidase subunit IV isoform 1 (COX1) and 3-hydroxyacyl CoA dehydrogenase (HOAD) relative gene expression. To integrate metabolic patterns and gene expression, L-LDH, CS, COX and HOAD activities were also determined. For further estimation of biological stores oxidized during seasonal acclimatization, we determined the blood levels of glucose, lipids and lactate. The results indicated seasonal changes in energy content, different patterns in gene expression and reorganization of metabolic patterns during cool acclimatization with increased lipid oxidation. During warm acclimatization, however, energy consumption was mostly based on carbohydrates oxidation. The decrease of E c and COX1 activity in the warm exposed heart seem to be consistent with the OCLTT hypothesis, suggesting that the heart may be one of the first organs to be limited during seasonal warming. Overall, this study has profiled changes in energetics and metabolic patterns occurring at annual temperatures at which P. pagrus is currently farmed, suggesting that this species is living at the upper edge of their thermal window, at least during summer., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Vasiliki Makri reports financial support was provided by Hellenic Foundation for Research and Innovation. John A. Theodorou reports financial support was provided by EU-Greece Operational Program of Fisheries. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Transient Receptor Potential (TRP) channels, essential for sensing environmental stimuli, are widely distributed. Among them, thermosensory TRP channels play a crucial role in temperature sensing and regulation. Sebastes schlegelii, a significant aquatic economic species, exhibits sensitivity to temperature across multiple aspects. In this study, we identified 18 SsTRP proteins using whole-genome scanning. Motif analysis revealed motif 2 in all TRP proteins, with conserved motifs in subfamilies. TRP-related domains, anchored repeats, and ion-transmembrane domains were found. Chromosome analysis showed 18 TRP genes on 11 chromosomes and a scaffold. Phylogenetics classified SsTRPs into four subfamilies: TRPM, TRPA, TRPV, and TRPC. In diverse organisms, four monophyletic subfamilies were identified. Additionally, we identified key TRP genes with significantly upregulated transcription levels under short-term (30 min) and long-term (3 days) exposure at 24 °C (optimal elevated temperature) and 27 °C (critical high temperature). We propose that genes upregulated at 30 min may be involved in the primary response process of temperature sensing, while genes upregulated at 3 days may participate in the secondary response process of temperature perception. This study lays the foundation for understanding the regulatory mechanisms of TRPs responses to environmental stimuli in S. schlegelii and other fishes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Protein and lipid are two major components that undergo significant changes during processing of aquatic products. This study focused on the protein oxidation, protein conformational states, lipid oxidation and lipid molecule profiling of salted large yellow croaker during storage, and their correlations were investigated. The degree of oxidation of protein and lipid was time-dependent, leading to an increase in carbonyl content and surface hydrophobicity, a decrease in sulfhydryl groups, and an increase in conjugated diene, peroxide value and thiobarbituric acid reactive substances value. Oxidation caused protein structure denaturation and aggregation during storage. Lipid composition and content changed dynamically, with polyunsaturated phosphatidylcholine (PC) was preferentially oxidized compared to polyunsaturated triacylglycerol. Correlation analysis showed that the degradation of polyunsaturated key differential lipids (PC 18:2&#95;20:5, PC 16:0&#95;22:6, PC 16:0&#95;20:5, etc.) was closely related to the oxidation of protein and lipid. The changes in protein conformation and the peroxidation of polyunsaturated lipids mutually promote each other's oxidation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The content of membrane-bound methemoglobin (MtHb) in nucleated erythrocytes was studied in the black scorpionfish Scorpaena porcus (Linnaeus, 1758) in vitro. Spectral characteristics were determined for a whole hemolysate, a hemolysate obtained by stroma precipitation (a clarified hemolysate), and a resuspended stroma. The MtHb proportion in the erythrocyte stroma was found to exceed 80% (6.20 ± 0.59 µM). Clarified hemolysates were nearly free of MtHb (0.5 ± 0.2 µM). Membrane-bound ferric hemoglobin did not affect the erythrocyte resistance to osmotic shock. The osmotic fragility range was determined using a LaSca-TM laser microparticle analyzer (BioMedSystems, Russia) to be 102-136 mOsm/kg, much the same as in other bony fish species. A nitrite load (10 mg/L) significantly increased the MtHb content in the blood. However, the membrane-bound ferric hemoglobin content did not change significantly, amounting to 6.34 ± 1.09 µM (approximately 95%). The finding suggested a functional importance for MtHb present in the plasma membrane of nucleated erythrocytes. Membrane-bound MtHb was assumed to neutralize the external oxidative load and the toxic effect of hydrogen sulfide in bottom water layers, where the species lives., (© 2024. Pleiades Publishing, Ltd.)

Antarctic notothenioid fishes, inhabiting the oxygen-rich Southern Ocean, possess a polyglutamine and glutamic acid (poly Q/E) insertion mutation in the master transcriptional regulator of oxygen homeostasis, hypoxia- inducible factor-1α (HIF-1α). To determine if this mutation impairs the ability of HIF-1 to regulate gene expression in response to hypoxia, we exposed Notothenia coriiceps, with a poly Q/E insertion mutation in HIF-1α that is 9 amino acids long, to hypoxia (2.3 mg L -1 O 2 ) or normoxia (10 mg L -1 O 2 ) for 12 h. Heart ventricles, brain, liver, and gill tissue were harvested and changes in gene expression quantified using RNA sequencing. Levels of glycogen and lactate were also quantified to determine if anaerobic metabolism increases in response to hypoxia. Exposure to hypoxia resulted in 818 unique differentially expressed genes (DEGs) in liver tissue of N. coriiceps. Many hypoxic genes were induced, including ones involved in the MAP kinase and FoxO pathways, glycolytic metabolism, and vascular remodeling. In contrast, there were fewer than 104 unique DEGs in each of the other tissues sampled. Lactate levels significantly increased in liver in response to hypoxia, indicating that anaerobic metabolism increases in response to hypoxia in this tissue. Overall, our results indicate that the hypoxia response pathway is functional in N. coriiceps despite a poly Q/E mutation in HIF-1α, and confirm that Antarctic fishes are capable of altering gene expression in response to hypoxia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Black porgy (Acanthopagrus schlegelii) is an important marine aquaculture species in China. It is an ideal object for the cultivation of low-salinity aquaculture strains in marine fish and the study of salinity tolerance mechanisms in fish because of its strong low-salinity tolerance ability. Gill is the main osmoregulatory organ in fish, and the liver plays an important role in the adaptation of the organism to stressful environments. In order to understand the coping mechanisms of the gills and livers of black porgy in different salinity environments, this study explored these organs after 30 days of culture in hypoosmotic (0.5 ppt), isosmotic (12 ppt), and normal seawater (28 ppt) at histologic, physiologic, and transcriptomic levels. The findings indicated that gill exhibited a higher number of differentially expressed genes than the liver, emphasizing the gill's heightened sensitivity to salinity changes. Protein interaction networks and enrichment analyses highlighted energy metabolism as a key regulatory focus at both 0.5 ppt and 12 ppt salinity in gills. Additionally, gills showed enrichment in ions, substance transport, and other metabolic pathways, suggesting a more direct regulatory response to salinity stress. The liver's regulatory patterns at different salinities exhibited significant distinctions, with pathways and genes related to metabolism, immunity, and antioxidants predominantly activated at 0.5 ppt, and molecular processes linked to cell proliferation taking precedence at 12 ppt salinity. Furthermore, the study revealed a reduction in the volume of the interlamellar cell mass (ILCM) of the gills, enhancing the contact area of the gill lamellae with water. At 0.5 ppt salinity, hepatic antioxidant enzyme activity increased, accompanied by oxidative stress damage. Conversely, at 12 ppt salinity, gill NKA activity significantly decreased without notable changes in liver structure. These results underscore the profound impact of salinity on gill structure and function, highlighting the crucial role of the liver in adapting to salinity environments., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier Inc.)

Declining flesh quality has drawn considerable attention in the farmed large yellow croaker (LYC; Larimichthys crocea) industry. Inosine monophosphate (IMP) is the primary flavor substance in aquatic animals. Adenosine monophosphate deaminase 1 (AMPD1) plays a critical role in IMP formation by catalyzing the deamination of AMP to IMP in the purine nucleotide cycle. To further evaluate the correlation between ampd1 mRNA expression levels and IMP content in the LYC muscle tissue, the relevant open reading frame (ORF) of L. crocea (Lcampd1) was cloned, and the IMP content and Lcampd1 mRNA expression in the muscles of LYCs of different sizes were examined. The ORF cDNA of Lcampd1 was 2211 bp in length and encoded a polypeptide of 736 amino acids (AAs). The deduced protein, LcAMPD1, possesses conserved AMPD active regions (SLSTDDP) and shows high homology with AMPD proteins of other teleost fishes. The genomic DNA sequence of Lcampd1 exhibits a high degree of evolutionary conservation in terms of structural organization among species. Phylogenetic analysis of the deduced AA sequence revealed that teleost fish and mammalian AMPD1 were separate from each other and formed a cluster with AMPD3, suggesting that AMPD1 and AMPD3 arose by duplication of a common primordial gene. In healthy LYC, Lcampd1 mRNA was expressed only in the muscle tissue. The IMP content in the muscle of LYCs with different average body weights was measured by high-performance liquid chromatography; the results showed that the IMP content in the muscle of LYCs with greater body weight was significantly higher than that in LYC with lower body weight. Moreover, a similar trend in Lcampd1 expression was observed in these muscle tissues. The Pearson correlation analysis further showed that the Lcampd1 mRNA expression was positively correlated with IMP content in the muscles of different-sized LYCs. These results suggest the potential function of Lcampd1 in determining the IMP content in LYC and provide a theoretical basis for flesh quality improvement, as well as a scientific basis for the development of the molecular breeding of LYC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Myocyte-specific enhancer binding factor 2 (MEF2), which belongs to the MADS superfamily, is a pivotal and conserved transcription factor that combines with the E-box motif to control the expression of muscle genes. Myostatin (mstn), a muscle growth inhibitor, is a vital member of the TGF-β superfamily. Currently, an understanding of the mechanisms of A. latus mstn (Almstn) transcriptional regulation mediated by MEF2 in fish muscle development is lacking. In the present study, two AlMEF2s (AlMEF2A and AlMEF2B) and Almstn2a were characterized from Acanthopagrus latus. AlMEF2A and AlMEF2B had 456 and 315 amino acid (aa) residues, respectively. Two typical regions, a MADS-box, MEF2, and transcriptionally activated (TAD) domains, are present in both AlMEF2s. The expression profiles of the two AlMEF2 genes were similar. The AlMEF2 genes were mainly expressed in the brain, white muscle, and liver, while Almstn2a expression was higher in the brain than in other tissues. Moreover, the expression trends of AlMEF2s and Almstn2a were significantly changed after starvation and refeeding in the five groups. Additionally, truncation experiments showed that -987 to +168 and -105 to +168 were core promoters of Almstn2a that responded to AlMEF2A and AlMEF2B, respectively. The point mutation experiment confirmed that Almstn2a transcription relies on the mutation binding sites 1 or 5 (M1/5) and mutation binding sites 4 or 5 (M4/5) for AlMEF2A and AlMEF2B regulation, respectively. The electrophoretic mobile shift assay (EMSA) further verified that M1 (-527 to -512) was a pivotal site where AlMEF2A acted on the Almstn2a gene. Furthermore, a siRNA interference gene expression experiment showed that reduced levels of AlMEF2A or AlMEF2B could prominently increase Almstn2a transcription. These results provide new information about the regulation of Almstn2a transcriptional activity by AlMEF2s and a theoretical basis for the regulatory mechanisms involved in muscle development in fish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Quantifying the tropic position (TP) of an animal species is key to understanding its ecosystem function. While both bulk and compound-specific analyses of stable isotopes are widely used for this purpose, few studies have assessed the consistency between and within such approaches. Champsocephalus gunnari is a specialist teleost that predates almost exclusively on Antarctic krill Euphausia superba . This well-known and nearly constant trophic relationship makes C. gunnari particularly suitable for assessing consistency between TP methods under field conditions. In the present work, we produced and compared TP estimates for C. gunnari and its main prey using a standard bulk and two amino acid-specific stable isotope approaches (CSI-AA). One based on the difference between glutamate and phenylalanine (TP Glx-Phe ), and the other on the proline-phenylalanine difference (TP Pro-Phe ). To do that, samples from C. gunnari, E. superba and four other pelagic invertebrate and fish species, all potential prey for C.gunnari, were collected off the South Orkney Islands between January and March 2019, analyzed using standard isotopic ratio mass spectrometry methods and interpreted following a Bayesian approach. Median estimates (CI 95% ) for C. gunnari were similar between TP bulk (3.6; CI 95% : 3.0-4.8) and TP Glx-Phe (3.4; CI 95% :3.2-3.6), and lower for TP Pro-Phe (3.1; CI 95% :3.0-3.3). TP differences between C. gunnari and E. superba were 1.4, 1.1 and 1.2, all compatible with expectations from the monospecific diet of this predator (ΔTP=1). While these results suggest greater accuracy for Glx-Phe and Pro-Phe, differences observed between both CSI-AA approaches suggests these methods may require further validation before becoming a standard tool for trophic ecology., Competing Interests: The authors declare there are no competing interests., (©2024 Canseco et al.)

Peptides possessing antihypertensive attributes via inhibiting the angiotensin-converting enzyme (ACE) were derived through the enzymatic degradation of Trichiurus lepturus (ribbonfish) using alkaline protease. The resulting mixture underwent filtration using centrifugation, ultrafiltration tubes, and Sephadex G-25 gels. Peptides exhibiting ACE-inhibitory properties and DPPH free-radical-scavenging abilities were isolated and subsequently purified via LC/MS-MS, leading to the identification of over 100 peptide components. In silico screening yielded five ACE inhibitory peptides: FAGDDAPR, QGPIGPR, IFPRNPP, AGFAGDDAPR, and GPTGPAGPR. Among these, IFPRNPP and AGFAGDDAPR were found to be allergenic, while FAGDDAPRR, QGPIGPR, and GPTGPAGP showed good ACE-inhibitory effects. IC 50 values for the latter peptides were obtained from HUVEC cells: FAGDDAPRR (IC 50 = 262.98 μM), QGPIGPR (IC 50 = 81.09 μM), and GPTGPAGP (IC 50 = 168.11 μM). Peptide constituents derived from ribbonfish proteins effectively modulated ACE activity, thus underscoring their therapeutic potential. Molecular docking and modeling corroborated these findings, emphasizing the utility of functional foods as a promising avenue for the treatment and prevention of hypertension, with potential ancillary health benefits and applications as substitutes for synthetic drugs.

Functions of vitellogenins have been in the limelight of fish reproductive physiology research for decades. The Vtg system of acanthomorph teleosts consists of two complete forms of Vtgs (VtgAa and VtgAb) and an incomplete form, VtgC. Insufficient uptake and processing of Vtgs and their yolk proteins lead to inadequate oocyte hydration ensuing failure in acquisition of egg buoyancy and early developmental deficiencies. This review presents a summary of our studies on utilization of multiple Vtgs in species with different egg buoyancy characteristics, as examples. Studies of moronids revealed limited degradation of all three forms of lipovitellin heavy chain derived from their three respective forms of Vtg, by which they contribute to the free amino acid pool driving oocyte hydration during oocyte maturation. In later studies, CRISPR/Cas9 was employed to invalidate zebrafish type I, type II and type III Vtgs, which are orthologs of acanthamorph VtgAa, VtgAb and VtgC, respectively. Results revealed type I Vtg to have essential developmental and nutritional functions in both late embryos and larvae. Genomic disturbance of type II Vtg led to high mortalities during the first 24 h of embryonic development. Despite being a minor form of Vtg in zebrafish and most other species, type III Vtg was also found to contribute essentially to the developmental potential of zebrafish zygotes and early embryos. Apart from severe effects on progeny survival, these studies also disclosed previously unreported regulatory effects of Vtgs on fecundity and fertility, and on embryo hatching. We recently utilized parallel reactions monitoring based liquid chromatography tandem mass spectrometry to assess the processing and utilization of lipovitellins derived from different forms of Vtg in Atlantic halibut and European plaice. Results showed the Lv heavy chain of VtgAa (LvHAa) to be consumed during oocyte maturation and the Lv light chain of VtgAb (LvLAb) to be utilized specifically during late larval stages, while all remaining YPs (LvLAa, LvHAb, LvHC, and LvLC) were utilized during or after hatching up until first feeding in halibut. In plaice, all YPs except LvHAa, which similarly to halibut supports oocyte maturation, are utilized from late embryo to late larval development up until first feeding. The collective findings from these studies affirm substantial disparity in modes of utilization of different types of Vtgs among fish species with various egg buoyancy characteristics, and they reveal previously unknown regulatory functions of Vtgs in maintenance of reproductive assets such as maternal fecundity and fertility, and in embryonic hatching. Despite the progress that has been made over the past two decades by examining multiple Vtgs and their functions, a higher complexity of these systems with much greater diversity between species in modes of Vtg utilization is now evident. Further research is needed to reveal novel ways each species has evolved to utilize these complex multiple Vtg systems and to discover unifying principles for this evolution in fishes of diverse lineages, habitats and life history characteristics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

In black porgy (Acanthopagrus schlegelii), the brain-pituitary-testis (Gnrh-Gths-Dmrt1) axis plays a vital role in male fate determination and maintenance, and then inhibiting female development in further (puberty). However, the feedback of gonadal hormones on regulating brain signaling remains unclear. In this study, we conducted short-term sex steroid treatment and surgery of gonadectomy to evaluate the feedback regulation between the gonads and the brain. The qPCR results show that male phase had the highest gths transcripts; treatment with estradiol-17β (E2) or 17α-methyltestosterone (MT) resulted in the increased pituitary lhb transcripts. After surgery, apart from gnrh1, there is no difference in brain signaling genes between gonadectomy and sham fish. In the diencephalon/mesencephalon transcriptome, de novo assembly generated 283,528 unigenes; however, only 443 (0.16%) genes showed differentially expressed between sham and gonadectomy fish. In the present study, we found that exogenous sex steroids affect the gths transcription; this feedback control is related to the gonadal stage. Furthermore, gonadectomy may not affect gene expression of brain signaling (Gnrh-Gths axis). Our results support the communication between ovotestis and brain signaling (Gnrh-Gths-testicular Dmrt1) for the male fate., Competing Interests: Declaration of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Rationale: ADB-FUBIATA is one of the most recently identified new psychoactive substance (NPS) of synthetic cannabinoids. The co-use of in vitro (human liver microsomes) and in vivo (zebrafish) models offers abundant metabolites and may give a deep insight into the metabolism of NPS., Methods: In vivo and in vitro metabolic studies of new synthetic cannabinoid ADB-FUBIATA were carried out using zebrafish and pooled human liver microsome models. Metabilites were structurally characterized by liquid chromatography-high-resolution mass spectrometry., Results: In total, 18 metabolites were discovered and identified in the pooled human liver microsomes and zebrafish, including seventeen phase I metabolites and one phase II metabolite. The main metabolic pathways of ADB-FUBIATA were hydroxylation, dehydrogenation, N-dealkylation, amide hydrolysis, glucuronidation, and combination thereof., Conclusion: Hydroxylated metabolites can be recommended as metabolic markers for ADB-FUBIATA because of the structural characteristics and high intensity. These metabolism characteristics of ADB-FUBIATA were useful for its further forensic or clinical related investigations., (© 2024 John Wiley & Sons Ltd.)

It is widely known that all-female fish production holds economic value for aquaculture. Sebastes schlegelii , a preeminent economic species, exhibits a sex dimorphism, with females surpassing males in growth. In this regard, achieving all-female black rockfish production could significantly enhance breeding profitability. In this study, we utilized the widely used male sex-regulating hormone, 17α-methyltestosterone (MT) at three different concentrations (20, 40, and 60 ppm), to produce pseudomales of S. schlegelii for subsequent all-female offspring breeding. Long-term MT administration severely inhibits the growth of S. schlegelii , while short term had no significant impact. Histological analysis confirmed sex reversal at all MT concentrations; however, both medium and higher MT concentrations impaired testis development. MT also influenced sex steroid hormone levels in pseudomales, suppressing E2 while increasing T and 11-KT levels. In addition, a transcriptome analysis revealed that MT down-regulated ovarian-related genes ( cyp19a1a and foxl2 ) while up-regulating male-related genes ( amh ) in pseudomales. Furthermore, MT modulated the TGF-β signaling and steroid hormone biosynthesis pathways, indicating its crucial role in S. schlegelii sex differentiation. Therefore, the current study provides a method for achieving sexual reversal using MT in S. schlegelii and offers an initial insight into the underlying mechanism of sexual reversal in this species.

Fish have common neurotransmitter pathways with humans, exhibiting a significant degree of conservation and homology. Thus, exposure to fluoxetine makes fish potentially susceptible to biochemical and physiological changes, similarly to what is observed in humans. Over the years, several studies demonstrated the potential effects of fluoxetine on different fish species and at different levels of biological organization. However, the effects of parental exposure to unexposed offspring remain largely unknown. The consequences of 15-day parental exposure to relevant concentrations of fluoxetine (100 and 1000 ng/L) were assessed on offspring using zebrafish as a model organism. Parental exposure resulted in offspring early hatching, non-inflation of the swimming bladder, increased malformation frequency, decreased heart rate and blood flow, and reduced growth. Additionally, a significant behavioral impairment was also found (reduced startle response, basal locomotor activity, and altered non-associative learning during early stages and a negative geotaxis and scototaxis, reduced thigmotaxis, and anti-social behavior at later life stages). These behavior alterations are consistent with decreased anxiety, a significant increase in the expression of the monoaminergic genes slc6a4a (sert), slc6a3 (dat), slc18a2 (vmat2), mao, tph1a, and th2, and altered levels of monoaminergic neurotransmitters. Alterations in behavior, expression of monoaminergic genes, and neurotransmitter levels persisted until offspring adulthood. Given the high conservation of neuronal pathways between fish and humans, data show the possibility of potential transgenerational and multigenerational effects of pharmaceuticals' exposure. These results reinforce the need for transgenerational and multigenerational studies in fish, under realistic scenarios, to provide realistic insights into the impact of these pharmaceuticals., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Daniela Correia reports financial support was provided byFoundation for Science and Technology. Miguel Oliveira reports was provided by Foundation for Science and Technology. Melissa Faria reports was provided by Severo Ochoa Centre of Excellence, IDAEA - CSIC. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We compared the endocrine status of the pituitary-gonad axis of wild and captive-reared greater amberjack (Seriola dumerili) during the reproductive cycle (April - July), reporting on the expression and release of the two gonadotropins for the first time in the Mediterranean Sea. Ovaries from wild females were characterized histologically as DEVELOPING in early May and SPAWNING capable in late May-July, the latter having a 3 to 4-fold higher gonadosomatic index (GSI). SPAWNING capable wild females exhibited an increase in pituitary follicle stimulating hormone (Fsh) content, plasma testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P), while almost a 10-fold increase was observed in pituitary luteinizing hormone (Lh) content. An increasing trend of plasma 17β-estradiol (E 2 ) was also recorded between the two reproductive stages in wild females. Captive-reared females sampled during the reproductive cycle exhibited two additional reproductive categories, with REGRESSED females having extensive follicular atresia and fish in the REGENERATING stage having only primary oocytes in their ovaries. Pituitary content of Fsh and Lh, fshb and lhb expression and plasma levels of Fsh and Lh remained unchanged among the four reproductive stages in captive females, in contrast with plasma E 2 and T that decreased in the REGENERATING stage, and 17,20β-P which increased after the DEVELOPING stage. In general, no significant hormonal differences were recorded between captive-reared and wild DEVELOPING females, in contrast to SPAWNING capable females, where pituitary Lh content, plasma Fsh and T were found to be lower in females in captivity. Overall, the captive females lagged behind in reproductive development compared to the wild ones and this was perhaps related to the multiple handling of the sea cages where all the sampled fish were maintained. Between wild males in the DEVELOPING and SPAWNING capable stages, pituitary Lh content, plasma T and 17,20β-P, and GSI exhibited 3 to 4-fold increases, while an increasing trend of pituitary Fsh content, lhb expression levels and plasma 11-ketotestosterone (11-KT) was also observed, and an opposite trend was observed in plasma Lh. Captive males were allocated to one more category, with REGRESSED individuals having no spermatogenic capacity. During the SPAWNING capable phase, almost all measured parameters were lower in captive males compared to wild ones. More importantly, captive males showed significant differences from their wild counterparts throughout the reproductive season, starting already from the DEVELOPING stage. Therefore, it appears that captivity already exerted negative effects in males prior to the onset of the study and the multiple handling of the cage where sampled fish were reared. Overall, the present study demonstrated that female greater amberjack do undergo full vitellogenesis in captivity, albeit with some dysfunctions that may be related to the husbandry of the experiment, while males, on the other hand, may be more seriously affected by captivity even before the onset of the study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The genome evolution of Antarctic notothenioids has been modulated by their extreme environment over millennia and more recently by human-caused constraints such as overfishing and climate change. Here we investigated the characteristics of the immune system in Notothenia rossii and how it responds to 8 h immersion in viral (Poly I:C, polyinosinic: polycytidylic acid) and bacterial (LPS, lipopolysaccharide) proxies. Blood plasma antiprotease activity and haematocrit were reduced in Poly I:C-treated fish only, while plasma protein, lysozyme activity and cortisol were unchanged with both treatments. The skin and duodenum transcriptomes responded strongly to the treatments, unlike the liver and spleen which had a mild response. Furthermore, the skin transcriptome responded most to the bacterial proxy (cell adhesion, metabolism and immune response processes) and the duodenum (metabolism, response to stress, regulation of intracellular signal transduction, and immune system responses) to the viral proxy. The differential tissue response to the two proxy challenges is indicative of immune specialisation of the duodenum and the skin towards pathogens. NOD-like and C-type lectin receptors may be central in recognising LPS and Poly I:C. Other antimicrobial compounds such as iron and selenium-related genes are essential defence mechanisms to protect the host from sepsis. In conclusion, our study revealed a specific response of two immune barrier tissue, the skin and duodenum, in Notothenia rossii when exposed to pathogen proxies by immersion, and this may represent an adaptation to pathogen infective strategies., Competing Interests: Conflicts of interest The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)