Transcriptome analyses in juvenile yellow perch (Perca flavescens) exposed in vivo to clothianidin and chlorantraniliprole: Possible sampling bias.

The St. Lawrence River is an important North American waterway that is subject to anthropogenic pressures including intensive urbanization, and agricultural development. Pesticides are widely used for agricultural activities in fields surrounding the yellow perch (Perca flavescens) habitat in Lake St. Pierre (Quebec, Canada), a fluvial lake of the river where the perch population has collapsed. Clothianidin and chlorantraniliprole were two of the most detected insecticides in surface waters near perch spawning areas. The objectives of the present study were to evaluate the transcriptional and biochemical effects of these two pesticides on juvenile yellow perch exposed for 28d to environmental doses of each compound alone and in a mixture under laboratory/aquaria conditions. Hepatic mRNA-sequencing revealed an effect of chlorantraniliprole alone (37 genes) and combined with clothianidin (251 genes), but no effects of clothianidin alone were observed in perch. Dysregulated genes were mostly related to circadian rhythms and to Ca2+ signaling, the latter effect has been previously associated with chlorantraniliprole mode of action in insects. Moreover, chronic exposure to clothianidin increased the activity of acetylcholinesterase in the brain of exposed fish, suggesting a potential non-target effect of this insecticide. Further analyses of three clock genes by qRT-PCR suggested that part of the observed effects of chlorantraniliprole on the circadian gene regulation of juvenile perch could be the result of time-of-day of sacrifice. These results provide insight into biological effects of insecticides in juvenile perch and highlight the importance of considering the circadian rhythm in experimental design and results analyses.

Paternal-effect-genes revealed through sperm cryopreservation in Perca fluviatilis.

Knowledge about paternal-effect-genes (PEGs) (genes whose expression in the progeny is influenced by paternal factors present in the sperm) in fish is very limited. To explore this issue, we used milt cryopreservation as a specific challenge test for sperm cells, thus enabling selection amidst cryo-sensitivity. We created two groups of Eurasian perch (Perca fluviatilis) as a model - eggs fertilized either with fresh (Fresh group) or cryopreserved (Cryo group) milt from the same male followed by phenotypic-transcriptomic examination of consequences of cryopreservation in obtained progeny (at larval stages). Most of the phenotypical observations were similar in both groups, except the final weight which was higher in the Cryo group. Milt cryopreservation appeared to act as a "positive selection" factor, upregulating most PEGs in the Cryo group. Transcriptomic profile of freshly hatched larvae sourced genes involved in the development of visual perception and we identified them as PEGs. Consequently, larvae from the Cryo group exhibited enhanced eyesight, potentially contributing to more efficient foraging and weight gain compared to the Fresh group. This study unveils, for the first time, the significant influence of the paternal genome on the development of the visual system in fish, highlighting pde6g, opn1lw1, and rbp4l as novel PEGs.

Water quality in a shallow eutrophic lake is unaffected by extensive thinning of planktivorous and benthivorous fish species.

Ambitious to fulfill the European Water Framework Directive obligations, the European governments support projects to rehabilitate lakes with poor water quality. However, most lake restorations having relied on biomanipulation by fish thinning have failed to improve or even maintain water quality. Previous attempts removed all target fish species simultaneously, thus making it impossible to assess the specific impact of each feeding group on water chemistry. Lake Bromme was selected for extensive, time-selective fish biomanipulation to improve water clarity and promote submerged macrophytes and piscivorous fish stocks over a three-year monitoring period. Thinning of adult benthivorous bream (Abramis brama) and tench (Tinca tinca) was conducted throughout year one while thinning in years two and three targeted planktivorous roach (Rutilus rutilus), juvenile bream, and small perch (Perca fluviatilis). Yearly fish surveys assessed changes in fish population structure and biomass. Water quality parameters were monitored continually, and the cover of submerged macrophytes was surveyed annually via sonar. We found no improvement in water clarity or reductions of nutrients, organic particles, chlorophyll concentrations, or watercolor, despite a 6-fold thinning of total estimated fish biomass, from 112 to 19 kg ha-1. Over the period, the macrophyte cover increased from 0.8 to 13.5 %, but no recruitment of large piscivorous fish (perch and pike (Esox lucius) > 10 cm) was detected. We found higher correlations of particle concentration and water clarity to water temperature than to wind speed, which indicates sediment particle resuspension by the remaining fish community (mostly carp Cyprinus carpio) that forage on benthos in shallow lakes. Further system-ecological research in Lake Bromme should evaluate whether thinning the stock of carp and increasing plant cover may improve water quality and test which optical properties sustain high water turbidity and prevent shallow, eutrophic lakes like Lake Bromme from responding to intense fish thinning.

Differing physiological performance of coexisting cool- and warmwater fish species under heatwaves in the Midwestern United States.

Heatwaves are becoming more frequent and intensified with climate change. Freshwater ecosystems are among the most threatened, within which, differing responses between cool- and warmwater species to heatwaves can lead to fundamental changes in communities. Physiological experiments can identify potential mechanisms underlying the impacts of such heatwaves on fish communities. In the current study, we quantified the oxygen consumption rate, aerobic scope and swimming performance of cool- and warmwater fish species following the simulation of short-term heatwaves currently occurring in streams in the Midwestern United States. The coolwater predator walleye (Sander vitreus) showed clear thermal disadvantages relative to the warmwater predator largemouth bass (Micropterus salmoides), based on a high metabolic cost during the heatwave, low metabolic activity when encountering prey, and reduced swimming performance following the heatwave. Largemouth bass also showed a thermal advantage relative to the warmwater prey fathead minnow (Pimephales promelas) related to swimming performance and energetic costs, highlighting differing thermal responses between predators and prey. This study demonstrates the importance of considering short-term extreme thermal events in the response of aquatic communities to climate stressors.

Taxonomic revision of the Pirate Perches, Aphredoderus, (Percopsiformes: Aphredoderidae) with descriptions of two new species.

Pirate Perches, Aphredoderus, are a widespread lowland freshwater fish native to the Eastern half of the United States. Aphredoderus was thought to contain a single species divided into an Eastern and Western subspecies on either side of the Appalachian Mountains with a widespread intergrade zone through much of the Eastern Gulf of Mexico and Southern Atlantic drainages. We use morphology and genetic data from specimens spanning the entire range of the genus to determine species limits within Aphredoderus. We find evidence of five species, four of which exhibit widespread sympatry in the Southeastern United States. We elevate A. sayanus sayanus and A. sayanus gibbosus to species, redescribe A. mesotrema, supplement previous descriptions, and describe two new species, A. retrodorsalis, and A. ornatus.

Sea perch (Lateolabrax japonicus) UBC9 augments RGNNV infection by hindering RLRs-interferon response.

Small ubiquitin-like modifier (SUMO) is a reversible post-translational modification that regulates various biological processes in eukaryotes. Ubiquitin-conjugating enzyme 9 (UBC9) is the sole E2-conjugating enzyme responsible for SUMOylation and plays an important role in essential cellular functions. Here, we cloned the UBC9 gene from sea perch (Lateolabrax japonicus) (LjUBC9) and investigated its role in regulating the IFN response during red-spotted grouper nervous necrosis virus (RGNNV) infection. The LjUBC9 gene consisted of 477 base pairs and encoded a polypeptide of 158 amino acids with an active site cysteine residue and a UBCc domain. Phylogenetic analysis showed that LjUBC9 shared the closest evolutionary relationship with UBC9 from Paralichthys olivaceus. Tissue expression profile analysis demonstrated that LjUBC9 was significantly increased in multiple tissues of sea perch following RGNNV infection. Further experiments showed that overexpression of LjUBC9 significantly increased the mRNA and protein levels of RGNNV capsid protein in LJB cells infected with RGNNV, nevertheless knockdown of LjUBC9 had the opposite effect, suggesting that LjUBC9 exerted a pro-viral effect during RGNNV infection. More importantly, we found that the 93rd cysteine is crucial for its pro-viral effect. Additionally, dual luciferase assays revealed that LjUBC9 prominently attenuated the promoter activities of sea perch type Ⅰ interferon (IFN) in RGNNV-infected cells, and overexpression of LjUBC9 markedly suppressed the transcription of key genes associated with RLRs-IFN pathway. In summary, these findings elucidate that LjUBC9 impairs the RLRs-IFN response, resulting in enhanced RGNNV infection.

Integrating fish swimming abilities into rapid road crossing barrier assessment: Case studies in the southeastern United States.

Many aquatic networks are fragmented by road crossing structures; remediating these barriers to allow fish passage is critical to restoring connectivity. Maximizing connectivity requires effective barrier identification and prioritization, but many barrier prioritization efforts do not consider swimming capabilities of target species. Given the many potential barriers within watersheds, inventory efforts integrating species-specific swimming speeds into rapid assessment protocols may allow for more accurate barrier removal prioritization. In this study, we demonstrate an approach for integrating fish swimming speeds into rapid barrier assessment and illustrate its utility via two case studies. We measured critical swimming speeds (Ucrit) of two stream-resident fish species with very different swimming modes: Yoknapatawpha Darter (Etheostoma faulkneri), an at-risk species whose current distribution is restricted to highly degraded habitat, and Bluehead Chub (Nocomis leptocephalus), an important host species for the federally endangered Carolina Heelsplitter mussel (Lasmigona decorata). We assessed potential barriers for Yoknapatawpha Darters in the Mississippi-Yocona River watershed, and Bluehead Chubs in the Stevens Creek watershed, South Carolina, USA. We integrated Ucrit into the Southeast Aquatic Resources Partnership (SARP) barrier assessment protocol by estimating the proportion of individuals per species swimming at least as fast as the current through the assessed structures. Integrating Ucrit estimates into the SARP protocol considerably increased barrier severity estimates and rankings only for Yoknapatawpha Darters in the Yocona River watershed. These results indicate the importance of including species-specific swimming abilities in rapid barrier assessments and the importance of species-watershed contexts in estimating where swimming speed information might be most important. Our method has broad application for those working to identify barriers more realistically to improve species-specific fish passage. This work represents a next step in improving rapid barrier assessments and could be improved by investigating how results change with different measurements of swimming abilities and structure characteristics.

Effect of type and concentration of antioxidant on sperm motility, viability, and DNA integrity of climbing perch Anabas testudineus Bloch, 1792 (Pisces: Anabantidae) post-cryopreservation.

Sperm quality is preserved through the crucial involvement of antioxidants, which play a vital role in minimizing the occurrence of reactive oxygen species (ROS) during the cryopreservation process. The suitability of the type and concentration of antioxidants are species-dependent, and this study is crucial in order to improve the quality of the climbing perch sperm post-cryopreservation. Therefore, this study aimed to determine the best type and concentration of antioxidants for cryopreservation of climbing perch Anabas testudineus sperm. To achieve this, 6 types of antioxidants, namely, ascorbic acid, beta-carotene, glutathione, butylated hydroxytoluene (BHT), myo-inositol, and alpha-tocopherol, with inclusion of a control were tested in 3 replications at three concentration levels of 0 mg/L (control), 20 mg/L, 40 mg/L, and 60 mg/L. Sperm was diluted in a glucose-base extender at a ratio of 1:60 (sperm: glucose base), then 10 % DMSO and 5 % egg yolk was added before cryopreservation for two weeks. The results showed that the type and concentration of antioxidants had a significant effect on the motility and viability of cryopreserved climbing perch sperm (P < 0.05), where the best results for ascorbic acid, beta-carotene, glutathione, myo-inositol, and alpha-tocopherol were obtained at a concentration of 60 mg/L, while BHT was at a concentration of 20 mg/L. The best results for glutathione, myo-inositol, and alpha-tocopherol were significantly different from other treatments, while the best results for ascorbic acid and beta-carotene (60 mg/L) were not significantly different from the 40 mg/L concentration, while the best results for BHT were not significantly different from the control treatments. Therefore, the best concentration of glutathione, myo-inositol, and alpha-tocopherol was 60 mg/L, while for ascorbic acid and beta-carotene it was 40 mg/L, and BHT was not recommended. DNA integrity analysis indicated the absence of fragmentation in all samples, including fresh, control, and treated sperm. Based on practical and economic considerations, myo-inositol at 60 mg/L was recommended for cryopreservation of climbing perch A. testudineus sperm.

Increasing mercury bioaccumulation and biomagnification rates of Nile perch (Lates niloticus L.) in Winam Gulf, Lake Victoria, Kenya.

The Nile perch (Lates niloticus L.) commercial fishery for Lake Victoria in East Africa is an important source of revenue and employment. We focused on shifts in food web structure and total mercury (THg) bioaccumulation and biomagnification in Nile perch, and lower food web items collected from Winam Gulf (Kenya) sampled 24 years apart (1998 and 2022). Stable isotope carbon (δ13C) values were higher in all species from 2022 compared to 1998. Stable nitrogen isotope (δ15N) values in baseline organisms were lower in 2022 compared to 1998. In Nile perch, δ15N values were correlated with total length, but the δ15N-length regressions were steeper in 1998 compared to 2022 except for one large (158 cm) Nile perch from 1998 with an uncharacteristically low δ15N value. Total Hg concentrations were lower in lower trophic species from 2022 compared to 1998. However, the THg bioaccumulation rate (as a function of fish length) in Nile perch was greater in 2022 compared to 1998 resulting in 24.2 % to 42.4 % higher wet weight dorsal THg concentrations in 2022 Nile perch for market slot size (50 to 85 cm) fish. The contrasting observations of increased THg bioaccumulation with size in 2022 against decreases in the rate of trophic increase with size and lower THg concentrations of lower food web items imply reduced fish growth and potential bioenergetic stressors on Winam Gulf Nile perch. All samples except 1 large Nile perch (139 cm total length collected in 2022) had THg concentrations below the European Union trade limit (500 ng/g wet weight). However, for more vulnerable individuals (women, children and frequent fish eaters), we recommend a decrease in maximum monthly meal consumption for 55-75 cm Nile perch from 16 meals per month calculated for 1998 to a limit of 8 meals per month calculated for 2022.

Haematological, biochemical, enzymological changes and mitochondrial dysfunction of liver in freshwater climbing perch Anabas testudineus during their acute and chronic exposure to sodium fluoride.

Anthropogenic activities are increasing fluoride concentration in watercourses. The present study focuses on the sublethal toxicity of sodium fluoride during sub-chronic and chronic time periods in the freshwater fish Anabas testudineus. The 96-hour LC50 value for fluoride was found to be 616.50 mg/L. Excessive mucous production and hyper excitability, followed by loss of balance, were seen in fish under acute fluoride exposure. Significant reduction in yield and specific growth rate of fish were assessed at 15, 30 and 45-days exposure intervals. Different bio-indicators like Hepatosomatic-index, Gonadosomatic-index and fecundity were reduced significantly in fish exposed to 10% (61.6 mg/L) and 20% (123.2 mg/L) of 96 h of LC50 values of fluoride in comparison to control. Toxicant concentrations directly correlated with parameter lowering. Fluoride exposure increased plasma glucose, creatinine, AST, and ALT and reduced total RBC, haemoglobin content, Hct (%), plasma protein, and cholesterol. Moreover, fluoride exposure significantly reduces the mitochondrial membrane potential in liver. This may result in metabolic depression, haematological, biochemical, and enzymological stress. The in-silico structural analysis predicts that fluoride may impede cytochrome c oxidase of the electron transport system, hence inhibiting mitochondrial functionality. These findings collectively highlight the urgent need for stringent regulation and monitoring of fluoride levels in freshwater ecosystems, as the subchronic and chronic effects observed in A. testudineus may have broader implications for aquatic ecosystems.

Temporal Trends of Great Lakes Legacy Contaminants: Ecological and Biological Considerations Applying the Age-Trend Model.

The USEPA Great Lakes Fish Monitoring and Surveillance Program (GLFMSP) has been monitoring top predator lake trout and walleye contaminant concentrations since the early 1970s. Our research revealed that select legacy contaminant groups (∑PCBs, ∑DDTs, ∑chlordanes, and ∑5PBDEs) have similar t1/2 and k2 values across the Great Lakes, with the exception of both Lake Erie sites and the Lake Superior─Keweenaw Point site. The slower halving times determined at both Lake Erie sites are consistent with legacy contaminant remobilization due to extreme weather climate effects and past remedial actions on the Detroit River, whereas the Lake Superior─Keweenaw Point site demonstrates contaminant halving times approaching the exponential minimum. Overall, Great Lakes select contaminant groupings have decreased between 25.8 and 97.9% since 2004. An age-normalized Great Lakes Contaminant Index (GLCI) was devised, indicating both Lake Michigan sites as the most highly impacted. The mean absolute deviation statistic was applied, documenting the need to age-correct contaminant trends due to highly variable age profiles. With the noted exceptions, the uniformity of age-corrected trend modeling suggests that a combination of the fundamental biological and physicochemical mechanisms of natural contaminant sequestration, declining dissolved water concentrations, accumulation/metabolism/depuration, and the overall reduction of legacy contaminant loading are driving the generally consistent rates of declines in the Great Lakes. Many of the biological and ecological stressors currently associated with climate change appear to be accounted for by the age-trend model.

DNA metabarcoding reveals spatial and temporal variation of fish eye fluke communities in lake ecosystems.

Eye flukes (Diplostomidae) are diverse and abundant trematode parasites that form multi-species communities in fish with negative effects on host fitness and survival. However, the environmental factors and host-related characteristics that determine species diversity, composition, and coexistence in such communities remain poorly understood. Here, we developed a cost-effective cox1 region-specific DNA metabarcoding approach to characterize parasitic diplostomid communities in two common fish species (Eurasian perch and common roach) collected from seven temperate lakes in Estonia. We found considerable inter- and intra-lake, as well as inter-host species, variation in diplostomid communities. Sympatric host species characterization revealed that parasite communities were typically more diverse in roach than perch. Additionally, we detected five positive and two negative diplostomid species associations in roach, whereas only a single negative association was observed in perch. These results indicate that diplostomid communities in temperate lakes are complex and dynamic systems exhibiting both spatial and temporal heterogeneity. They are influenced by various environmental factors and by host-parasite and inter-parasite interactions. We expect that the described methodology facilitates ecological and biodiversity research of diplostomid parasites. It is also adaptable to other parasite groups where it could serve to improve current understanding of diversity, distribution, and interspecies interactions of other understudied taxa.

Measuring Total Mercury Through Freeze-Thaw Cycles.

Total mercury (THg) analysis of fish tissue requires the samples to be frozen for long-term storage or analyzed immediately after the fish sample has been obtained. Such rigid field sampling protocols do not account for the logistical challenges that can occur if sampling is conducted in remote areas or collaboratively via community-based monitoring initiatives. Here we present a study that examines the loss of THg from Walleye tissue that has thawed for 3 and 5 days, mimicking potential thaw during transport from remote locations. THg concentrations were not significantly influenced (Kruskal-Wallace, p-value > 0.05) by the thaw and refreeze events. The mean THg concentration per day group was 0.67 ug/g, SD = 0.03, 0.65 ug/g, SD = 0.01, and 0.72 ug/g, SD = 0.01 for the control (no thaw), 3-day thaw and 5-day thaw, respectively. Results from this study suggest the analytical integrity of samples may be maintained if freeze-thaw situations arise when conducting community-based mercury monitoring programs.

Description, life cycle, and phylogenetics of Proterometra wigglewomble n. sp. (Digenea: Azygiidae) from the Cahaba River, Alabama, U.S.A.

We herein describe Proterometra wigglewomble n. sp. (Digenea: Azygiidae: Azygiinae) from the Cahaba River, Alabama, USA, which asexually reproduces in the compact elimia, Elimia showalteri (Lea, 1860) (Cerithioidea: Pleuroceridae) and matures in the oesophagus of the blackbanded darter, Percina nigrofasciata (Agassiz, 1854) (Perciformes: Percidae). Adults of the new species differ from congeners by having a small body and eggs having a wholly fimbriated surface that appears as a cilia-like brush border. Live naturally-shed cercariae of the new species differ from those of its congeners by having a strongly claviform tail stem bearing aspinose mammillae, a single furca, excretory pores that open on the posterior margin of the single furca, and few eggs in the cercarial distome. The behaviour of the cercaria further differentiates the new species. Naturally-shed cercariae of P. wigglewomble secrete a jelly-like adhesive that coats the surface of the furca and evidently facilitates attachment to the surface of glass, plastic, and snail shell. Attached cercariae vigorously wiggle and thrash about once attached, as if mimicking the larva of a stream insect so as to lure the blackbanded darter to eat it. Phylogenetic analyses recovered monophyletic Azygiidae, comprising monophyletic Leuceruthrinae Goldberger, 1911 and polyphyletic Azygiinae Lühe, 1909. The present study is the largest taxon sampling for Azygiidae and the first to include 28S sequences of Leuceruthrus. Compact elimia and blackbanded darter are new host records for Proterometra. The new species is the 3rd congener reported from the Cahaba River, a region renowned for its fish and snail endemic biodiversity.

Preparing for the future offspring: European perch (Perca fluviatilis) biosynthesis of physiologically required fatty acids for the gonads happens already in the autumn.

Long-chain polyunsaturated fatty acids (PUFA) are critical for reproduction and thermal adaptation. Year-round variability in the expression of fads2 (fatty acid desaturase 2) in the liver of European perch (Perca fluviatilis) in a boreal lake was tested in relation to individual variation in size, sex, and maturity, together with stable isotopes values as well as fatty acids (FA) content in different tissues and prey items. ARA and DHA primary production was restricted to the summer months, however, perch required larger amounts of these PUFA during winter, as their ARA and DHA muscle content was higher compared to summer. The expression of fads2 in perch liver increased during winter and was higher in mature females. Mature females stored DHA in their gonads already in late summer and autumn, long before the upcoming spring spawning period in May. Lower δ13CDHA values in the gonads in September suggest that these females actively synthesized DHA as part of this reproductive investment. Lower δ13CARA values in the liver of all individuals during winter suggest that perch were synthesizing essential FA to help cope with over-wintering conditions. Perch seem able to modulate its biosynthesis of physiologically required PUFA in situations of stress (fasting or cold temperatures) or in situations of high energetic demand (gonadal development). Biosynthesis of physiologically required PUFA may be an important part of survival and reproduction in aquatic food webs with long cold periods.

Ontogeny of the digestive enzyme activity of the pikeperch (Sander lucioperca) under culture condition.

The pikeperch (Sander lucioperca) is a species with a high potential for aquaculture and a valuable food with high market acceptance. The aim of the study was to evaluate the functional ontogeny of digestive enzyme of pikeperch from hatching to 45 days-post fertilization, 777 degree-day (DPF, dd) under culture condition. The average total length (TL) of larvae measured at hatching was 3.6 ± 0.4 mm (5 DPF; 67 dd) and at the end of experiment (45 DPF, 777 dd) was 27.1 ± 1.1 mm. The survival rate was 80-90% during the experiment period. Inhibition zimography reveals the presence of nine bands with proteolytic activity in the digestive tract of juvenile pikeperch. Zimography results during the ontogeny revealed that in larvae at 8 DPF (108 dd) and 13 DPF (189 dd), three bands were presented. The variations observed in the enzymatic activity reflected a high amount of total protease activity at 10 DPF (133.5 dd). Regarding pepsin, its activity was observed for the first time at 26 DPF (378.9 dd). Lipase activity remained constant from hatching to 26 DPF (378.9 dd). The highest amount of α-amylase activity was detected at 15 DPF (211.5 dd) and 45 DPF (777 dd). The low lipase enzyme activity suggested that live feeds with low lipid were more suitable than diets containing high lipid levels; larvae had also early capability to digest nutrient-dense diet that was high in protein. According to results the pikeperch larvae possess after the exogenous feeding, a functional digestive system with high activities that indicated the gradual development of the digestive system.

Growth and fatty acid composition of pikeperch (Sander lucioperca L., 1758) larvae under altered feeding protocol including the copepod Apocyclops panamensis (Marsh, 1913).

Alternative live feeds for small and sensitive fish early life stages such as pikeperch (Sander lucioperca L., 1758) can improve the larval quantity, quality and performance in aquaculture. Therefore, this study evaluated the cyclopoid copepod Apocyclops panamensis (Marsh, 1913) as live feed for pikeperch larviculture from day 11 post hatch (dph) in two independent experiments. In both experiments, pikeperch larvae had the highest specific growth rate (SGR) when they fed on Brachionus plicatilis until dph 11 and A. panamensis until dph 16-18. SGR was related to a decrease in total fatty acids (FAs), saturated FAs and monounsaturated FAs in pikeperch larvae, indicating their use as energy for growth. Within the polyunsaturated FAs, docosahexaenoic acid (DHA) increased in larvae fed with A. panamensis and coincided with the highest SGR suggesting that DHA is accumulated in larvae as structural FA. Our study demonstrated a suitable pikeperch larval fatty acid composition for growth after feeding A. panamensis compared with Artemia sp. from dph 11 until dph 16 and previously fed with B. plicatilis. Moreover, it highlighted the importance of the dietary PUFAs in pikeperch rearing, specifically of linoleic acid (LA) from dph 4 until dph 11 and of DHA from dph 11 onwards.

Are bold-shy personalities of European perch (Perca fluviatilis) linked to stress tolerance and immunity? A scope of harnessing fish behavior in aquaculture.

The sensitivity to stress and its impact on immunity are supposedly related to a fish's personality. In the present study, European perch (Perca fluviatilis) were exposed to an open-field and a novel-object test to identify distinctive shy and bold individuals. This series of cognitive tests revealed clear differences between proactive individuals with pronounced exploration behavior (bold personality) and reactive individuals that took a freeze-hide position (shy personality). A cohort of shy and bold perch was then exposed to elevated stocking density. Frozen activity and lower explorative behavior were related to higher basal and stocking-induced cortisol levels compared to proactive individuals. Since cortisol is a well-known modulator of immune-gene expression, we used multiplex real-time PCR to profile the differential immune responses to the intraperitoneal injection of Aeromonas hydrophila in the head kidney and peritoneal cells of bold and shy perch individuals. These expression differences between stimulated bold and shy perch were generally modest, except for the genes encoding the complement component c3 and the matrix metallopeptidase mmp9. The strong differential expression of these two bactericidal and inflammatory genes in the context of the modestly regulated features suggests that a fish's personality is linked to a particular immune-defense strategy. In conclusion, our approach, based on behavioral video observations, phagocytosis and enzyme assays, immunogene-expression profiling, and quantification of stress-relevant metabolites, revealed indications for divergent coping styles in cohorts of bold or shy European perch. This divergence could be exploited in future selective breeding programs.

Optimization of single-step gelatin extraction from pink perch (Nemipterus japonicus) skin and bone obtained from surimi industry using a green solvent.

Surimi industry produces a large quantity of byproducts that are currently being utilized to produce low-value commodities. This study aims to extract gelatin from pink perch skin and bone obtained from the surimi industry using a green single-step extraction method. In addition to using a green solvent, that is, acetic acid, the new method combines the multiple steps of pre-treatment and hydrolysis into one single-step extraction process. Response surface methodology was used to optimize extraction parameters (pH, temperature, and time) to maximize yield and l-hydroxyproline (l-hyp) content. The optimum condition for gelatin extraction was obtained at pH 3, 75°C, and 30 min. At optimum conditions, gelatin yield and l-hyp content were observed to be 16.07% and 41.26 mg g-1 , respectively. The gelatin obtained at optimized condition was further compared with commercial bovine gelatin (BG) in terms of chemical composition and textural, functional, and rheological properties. The results suggested that the optimized pink perch gelatin had higher protein content (92.06%), better gel strength (251.08 g), higher imino acid (18.01%), and improved textural and functional properties than the commercially available BG. The optimized single-step gelatin extraction method from pink perch skin and bones is a promising, rapid, and efficient method for the production of good-quality gelatin, which can be further used for the development of high-value products such as food formulations. PRACTICAL APPLICATION: Fish gelatin is widely used in food product development. Most of the existing methods of the development of high-value product such as gelatin, use multi-step process and harsh mineral acid, therefore, are time-consuming and harmful to the environment. This study provides a green single-step gelatin extraction method that provides an efficient, rapid, and convenient method of gelatin extraction and a sustainable solution for fish industry byproduct utilization. The data obtained with this laboratory-scale study provides a strong basis for scale-up studies.

DNA Methylation Profiling of Ovarian Tissue of Climbing Perch (Anabas testudienus) in Response to Monocrotophos Exposure.

Epigenetic modifications like DNA methylation can alter an organism's phenotype without changing its DNA sequence. Exposure to environmental toxicants has the potential to change the resilience of aquatic species. However, little information is available on the dynamics of DNA methylation in fish gonadal tissues in response to organophosphates. In the present work, reduced-representation bisulfite sequencing was performed to identify DNA methylation patterns in the ovarian tissues of Anabas testudienus exposed to organophosphates, specifically monocrotophos (MCP). Through sequencing, an average of 41,087 methylated cytosine sites were identified and distributed in different parts of genes, i.e., in transcription start sites (TSS), promoters, exons, etc. A total of 1058 and 1329 differentially methylated regions (DMRs) were detected as hyper-methylated and hypo-methylated in ovarian tissues, respectively. Utilizing whole-genome data of the climbing perch, the DMRs, and their associated overlapping genes revealed a total of 22 genes within exons, 45 genes at transcription start sites (TSS), and 218 genes in intergenic regions. Through gene ontology analysis, a total of 16 GO terms particularly involved in ovarian follicular development, response to oxidative stress, oocyte maturation, and multicellular organismal response to stress associated with reproductive biology were identified. After functional enrichment analysis, relevant DMGs such as steroid hormone biosynthesis (Cyp19a, 11-beta-HSD, 17-beta-HSD), hormone receptors (ar, esrrga), steroid metabolism (StAR), progesterone-mediated oocyte maturation (igf1ar, pgr), associated with ovarian development in climbing perch showed significant differential methylation patterns. The differentially methylated genes (DMGs) were subjected to analysis using real-time PCR, which demonstrated altered gene expression levels. This study revealed a molecular-level alteration in genes associated with ovarian development in response to chemical exposure. This work provides evidence for understanding the relationship between DNA methylation and gene regulation in response to chemicals that affect the reproductive fitness of aquatic animals.