Aquaculture

Selection for disease resistance forms one of the most highlighted areas of aquaculture breeding. A breeding program for Arctic charr has been operating in Sweden for over 40 years, making it the oldest of its kind worldwide for this species. However, the lack of available genomic resources prevented selection for any disease-resistance traits. A 72k Axiom SNP array was produced in this study and used to assess the potential to select for charr resistant to bacterial kidney disease (BKD), which is currently a major threat to the industry. Following a challenge experiment with Renibacterium salmoninarum, the causative agent of BKD, relevant phenotypic proxies were collected from approximately 2,000 charr. Thereafter, those animals were genotyped with the new 72k SNP array. The magnitude of the estimated variance components suggested potential for breeding for BKD resistance in charr, with relevant heritabilities ranging from 0.05 to 0.56 depending on the resistance proxy used. In addition, GWAS suggested that BKD resistance is a polygenic trait. Furthermore, genomic prediction approaches indicated that BKD-resistant animals can be identified using their SNP genotypes. Accuracies, expressed as Pearson correlation coefficients, when BKD resistance was analysed as a continuous trait, ranged from 0.42 to 0.52. In the scenario where BKD resistance was treated as a binary trait, the efficiency of genomic prediction was assessed using ROC curves, with an area under the curve of 0.72. Finally, no unfavourable correlations were found with growth traits. The developed 72k SNP array has the potential of being a pivotal tool for the Swedish Arctic charr breeding program. Moreover, our data support the use of genomic prediction in breeding BKD-resistant Arctic charr. As a critical next step, further validations in actual industry conditions would be required.

The slipper lobster (Thenus australiensis) is rapidly emerging as a high-potential species for commercial aquaculture. Because females exhibit superior growth characteristics due to less frequent moulting after sexual maturity, developing monosex breeding strategies is highly desirable for industry profitability. However, the lack of genomic resources and early sex-identification tools has hindered this development. Here, we report the first draft male genome assembly for T. australiensis, generated using a combination of whole-genome shotgun sequencing, DArT-seq, and multi-tissue transcriptomics. The curated assembly spans 0.913 Gbp with high functional completeness (93.0% BUSCO), providing a robust repertoire of 30,100 protein-coding genes. Through k-mer subtraction and population-level DArT-seq genotyping, we provide definitive evidence that T. australiensis utilizes an XX/XY sex-determination system. Crucially, by identifying male-specific structural variations within a neo-Y locus, we developed a diagnostic PCR assay targeting a male-exclusive sequence. This 171 bp marker achieved 100% accuracy in phenotypic sex identification across wild-caught populations. Ultimately, these foundational genomic resources, combined with a highly reliable molecular sexing tool, provide the critical framework necessary for early sex sorting, broodstock management, and the commercial advancement of monosex slipper lobster farming.

Understanding the genetic structure of keystone species within river networks is essential for effective conservation and management. While population differentiation of anadromous species often occurs between river systems, less research has been conducted on differentiation within rivers with smaller catchment areas. In this study, we investigated the population genetic structure of wild Atlantic salmon (Salmo salar) across the small-scale river Ronne [a] system in southernmost Sweden using Restriction-site Associated DNA sequencing (RADseq). Although the Admixture analysis did not detect clearly defined genetic clusters, significant pairwise FST values and DAPC revealed emerging population differentiation among the Ronne [a] tributaries. The observed patterns are consistent with a system characterized by connectivity, where genetic flow is present but can be reduced by behavioral and ecological factors such as spawning homing behavior and selective movements. These findings suggest that, despite overall connectivity, Atlantic salmon populations in the Ronne [a] catchment area may function as partially independent sub-populations. This highlights the importance of conservation and management strategies in fragmented river systems to consider population genetic structure to support resilient salmon populations under ongoing anthropogenic pressures.

Congenital disorders of glycosylation and deglycosylation are rare, serious, and lethal disorders afflicting humans. CDGs and CDDGs result in loss of function enzymes which fail to build or break down oligosaccharides on proteins. This can produce protein aggregates and, in turn, reactive oxygen species that harm the cell eventually leading to autophagy and apoptosis. Because sperm contain high concentrations of polyunsaturated fatty acids, they are especially sensitive to these effects, which is understood as one of the leading factors in human male infertility. Sperm are developed in zebrafish similarly to humans and are useful models to examine human reproductive health, as well as genetic disorders. The combination of these advantages makes the analysis of sperm from zebrafish with heterozygous ALG1 or DPAGT1 CDGs or the NGLY1 CDDG suitable. Analysis of sperm concentration, motility, status, viability, and hypoosmotic swelling demonstrated the effects of these disorders on sperm quality. Results showed a significant decrease in sperm concentration, motility, and hypoosmotic swelling for all mutant zebrafish compared to the wild type. This suggests that CDGs and CDDGs influence the amount of sperm produced, the percentage of sperm cells that are mobile, and the integrity of the plasma membrane.

The aim of this study was to evaluate the impact of two sustainable dietary protein sources on the structure and composition of the gut microbiota in European sea bass (Dicentrarchus labrax) juveniles. These protein sources were incorporated to the aquafeeds containing (a) Lupinus albus meal, treated with either exogenous enzymes (Solid state hydrolysis-SSH) or fermented with Saccharomyces cerevisiae (Solid state fermentation, SSF) and (b) Lagocephalus sceleratus meal. In the first case (a), the control aquafeed simulated a standard commercial diet, containing soybean meal whereas in the rest of the diets soybean meal was partially or totally replaced by hydrolysed or fermented Lupin meal. In the second case (b) the fish were fed Lagocephalus sceleratus unprocessed fishmeal as well as treated at different temperatures to deactivate tetrodotoxin (TTX). A control diet with 30% commercial fish meal was also fed as a reference diet. Both diets in all inclusion levels did not cause any significant gut microbiota change, suggesting their neutral role in this aspect. However, the gut bacterial communities of the fish fed with 12.5% lupin meal inclusion, had increased amino acid biosynthetic pathways suggesting a beneficial effect.

The moonfish Mene maculata (Bloch and Schneider, 1801), the sole extant species of the family Menidae, is widely distributed in the Indo-West Pacific. Although its spawning season has previously been inferred from seasonal variation in the gonadosomatic index (GSI), the histological basis for interpreting GSI as an indicator of spawning-capable status remains limited. Here we describe the gonadal structure of male and female M. maculata and evaluate how GSI and standard length relate to spawning-capable status based on germ cell development. The testis was lobular and exhibited an unrestricted spermatogonial distribution, a structure widely observed among neoteleosts, indicating that the phylogenetic distinctiveness of M. maculata was not associated with a distinctive testicular structure. In the spawning-capable female, oocytes at multiple developmental stages, from primary growth to oocyte maturation, co-occurred within the ovary, indicating asynchronous ovarian development. This finding suggests that M. maculata may be a batch spawner rather than a total spawner as previously inferred. The spawning-capable female had a GSI consistent with previously inferred spawning season estimates. By contrast, histologically examined males were spawning capable at GSI values lower than those previously associated with the inferred spawning season, suggesting that male spawning-capable status may persist beyond the period inferred from elevated GSI alone. This study provides the first histological description of reproductive biology in the phylogenetically distinctive M. maculata and establishes a histological basis for interpreting GSI as a reproductive indicator.

Cryopreservation of ram semen induces structural and functional alterations that compromise sperm fertility. Since seminal plasma contributes to the regulation and preservation of sperm function, increasing attention has been directed toward seminal plasma extracellular vesicles (EVs) that are involved in sperm physiology. EVs act as carriers of proteins that are involved in sperm membrane organization and capacitation, suggesting that they may contribute to the maintenance of sperm stability during cryopreservation.. Thus, the aim of this study was to evaluate the effect of seminal plasma-derived EVs on post-thaw functional parameters of ram sperm. Semen was cryopreserved in the presence or absence of EVs isolated by ultracentrifugation that have been characterized by nanoparticle tracking analysis (NTA) and Western blotting (WB). Post-thaw sperm quality was assessed by evaluating viability, membrane lipid disorder, reactive oxygen species production, protein phosphorylation, acrosome status, intracellular calcium levels, and sperm motility. Sperm cryopreserved with an extender containing EVs showed a significant reduction in membrane lipid disorder and lower intracellular calcium levels compared to control samples (p < 0.05). CASA analysis revealed that EV supplementation did not affect total or progressive motility but modified sperm kinematic patterns, with increased linearity and straightness, indicating improved trajectory efficiency without induction of hyperactivated motility. No differences were detected in viability, ROS content, phosphorylation of proteins in residuous tyrosine (pY) or PKA or acrosome status. These results provide the first evidence that seminal plasma derived extracellular vesicles exert a protective effect during ram semen cryopreservation, preserving membrane organization and calcium homeostasis and improving sperm functional quality after thawing. Highlights- Seminal EVs protect ram sperm during cryopreservation. - EVs reduce membrane lipid disorder and intracellular Ca2+ levels. - EVs modify kinematics, increasing linearity and straightness. - No effects on viability, ROS, phosphorylation or acrosome status. - EVs improve post-thaw sperm functional quality and stability. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/732841v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@d1f8a9org.highwire.dtl.DTLVardef@11c3d6aorg.highwire.dtl.DTLVardef@104124forg.highwire.dtl.DTLVardef@4e355f_HPS_FORMAT_FIGEXP M_FIG C_FIG

Here, we report the first genetic confirmation of golden mussels (Limnoperna fortunei) in North America, and the subsequent development, optimization, and deployment of golden mussel eDNA monitoring procedures. Aquatic species invasions are economically costly, disrupt ecosystem functionality, and impact native aquatic communities. Early detection of new invasive species enables rapid response via implementation of effective eradication or control measures and is key for reducing harmful outcomes. Initial species detection and taxonomic identification can be aided by genetic methods that have high detection sensitivity and accuracy. Genetic methods such as environmental DNA (eDNA) sampling can be used to detect invasive species before they become established in new systems, providing an early alert system to inform resource managers. Golden mussels were first detected in North America in October 2024 near the Port of Stockton in the San Francisco Estuary (SFE). The SFE is particularly vulnerable to invasion due to the access and connectivity provided by the presence of engineering infrastructure and shipping lanes. Collaborative efforts between public agencies and academic institutions are underway to develop a coordinated detection and response plan. Early detection followed by a rapid response is the best defense against prolific invasive species, such as the golden mussel.

Climate-driven warming is challenging the physiological limits of aquatic ectotherms, with cardiac performance emerging as one of the key determinants of thermal tolerance. Cardiac function relies on mitochondrial ATP production, and mitochondrial dysfunction has been linked to cardiac failure at critical temperatures. However, mitochondria are plastic and may represent a target for interventions aimed at improving thermal tolerance in fish. Exercise training improves whole-animal performance in fish, including cardiac thermal performance, and improves mitochondrial function in other taxa. However, its effects on the thermal sensitivity of cardiac mitochondria remain unknown. This study investigated whether exercise-training alters cardiac mitochondrial performance at optimal and critical temperatures in rainbow trout Oncorhynchus mykiss. Farmed rainbow trout were subjected to a four-week exercise training regime, while control fish remained under standard rearing conditions. Cardiac mitochondrial respiration was assessed in permeabilised heart fibres at 16{degrees}C (optimal growth temperature) and 26{degrees}C (temperature associated with cardiac arrhythmia) and several biochemical and nuclear indicators were measured. No significant differences were detected between treatments for any measured variable. However, trained fish generally exhibited higher maximal respiratory capacities and respiratory control ratios, particularly at the elevated temperature, suggesting subtle improvements in mitochondrial function despite considerable inter-individual variation. Temperature influenced mitochondrial performance, increasing proton leak and reducing coupling efficiency. These findings demonstrate that cardiac mitochondrial function is thermally sensitive and represents a potential targeted for improving thermal resilience in aquaculture species.

Biofilms on aquaculture infrastructure harbor diverse microbial communities that may influence water quality and fish health, yet the temporal dynamics of these communities remain poorly characterized. Here, we used 16S rRNA gene amplicon sequencing to profile biofilm communities on concrete raceway surfaces across an 80-day rainbow trout (Oncorhynchus mykiss) indoor hatch-house production period. One hundred twenty-three wall swab samples from 19 raceways at six time points (9, 23, 38, 53, 65, and 80 days) were analyzed after stringent quality control. Beta diversity analyses revealed that biofilm communities at each time point were significantly distinct (PERMANOVA, p < 0.001 for all pairwise comparisons), with early communities exhibiting greater variability than late-stage biofilms. Total bacterial load increased approximately 2.5-fold from early to late stages (qPCR, p < 0.001). Differential abundance testing (ANCOM-BC) identified 57 differentially abundant genera between early-and late-stage biofilms, and random forest classification distinguished early from late communities with over 93% test accuracy. A clear successional trajectory emerged: early biofilms were dominated by pioneer taxa including Pseudomonas, Caulobacter, and Flavobacterium; mid-succession communities featured predatory Bdellovibrio and the methylotroph Methylotenera; and mature biofilms were enriched in saprophytic Saprospiraceae and Haliscomenobacter, polysaccharide-degrading Verrucomicrobiaceae, and cooperative predatory myxobacteria. Flavobacterium columnare, a pathogen of concern in aquaculture, was detected at low levels throughout the production period. These results demonstrate predictable ecological succession in freshwater built environment biofilms and provide a foundation for understanding the role of surface-associated microbial communities in hatchery management.

The recent shift in Bangladesh from tradition backyard rearing system to modern commercial layer farming has made the birds immune to infectious diseases. Pediculosis, however, continues to pose a challenge in modern production system due to its invasive nature, often going unnoticed and neglected as it is typically non-lethal, yet capable of causing significant production losses. Lice infestation is a persistent threat in poultry production; however, its implications in battery-caged commercial layer hens in Bangladesh remain insufficiently characterized. The study aimed to identify the causative louse species and evaluate its associations with clinical pathology, hematological alteration and productive performance in 30 white-feathered (15 infested + 15 non-infested) and 30 brown-feathered (15 infested + 15 non-infested) laying birds from two commercial farms in Tangail. Morphological characterization confirmed the parasite as Menacanthus stamineus, distinguished by a dorsoventrally flattened body, parabolicallly rounded head wider than long, concealed club-shaped antennae, an oblong-oval abdomen with fine setae and three pairs of short legs each bearing paired claws. Infested birds exhibited consistent clinical pathology, including pale combs, petechial hemorrhages around the vent, severe feather damage with alopecic and exudative areas and incidence of irregular and broken-shelled eggs. Production performance analysis revealed significant reduction in hen-day egg production, egg weight, and feed intake, accompanied by significantly increased feed conversion ratios. Hematological evaluation demonstrated significantly reduced hemoglobin concentration, hematocrit and erythrocyte counts in infested hens, indicating mild anemia and compromised oxygen-carrying capacity. Collectively, pediculosis was strongly associated with lice-induced self-inflicted injury and cannibalism, systemic physiological stress, impaired erythropoiesis, reduced production efficiency and compromised welfare in caged laying hens. To best of our knowledge, it was the first integrative reports from Bangladesh documenting M. stramineus infestation in battery-caged commercial layer system with concurrent evidence of hematological disruption and measurable productivity losses, underscoring its epidemiological and economic significance and urgent need for targeted, evidence-based ectoparasite control strategies.

Absorption of CO2 by global oceans is decreasing pH resulting in ocean acidification (OA). Impacts on shellfish have been documented in ecologically and commercially important species. We examined the influence of diet and OA between two populations of red abalone (Haliotis rufescens) a species of aquaculture importance and declining wild populations. Populations experience different exposure histories: strong upwelling (Van Damme, California [VD]) historically exposed to low-pH conditions and weak-intermittent upwelling (Santa Barbara, California [SB]). Abalone were cultured under control-pH or OA-conditions and fed crustose coralline algae (CCA) or diatoms used in aquaculture. We tested treatment effects of population, settlement diet, and OA-exposure on survival as influenced by larval-energy stores. Survival in both populations was enhanced by CCA when cultured under both treatment conditions; however, by later stages, this effect remained only for SB. SB had reduced post-settlement survival when cultured under OA-conditions, whereas post-settlement survival of VD was not. Diet affected the relationship between larval-energy and post-settlement survival; a positive relationship when fed diatoms and a negative relationship with CCA. The relationship between larval energy and post-settlement survival was stronger in VD. CCA enhanced juvenile growth in SB cultured abalone at both three-months and one-year post-settlement. Settlement diets can reduce the impacts of OA on early-life stages of abalone, but population differences driven by underlying energetics affect the consistency of this outcome. These findings illuminate the impacts from OA, suggesting populations may be at risk, and inform strategies for developing and sustaining shellfish aquaculture in the face of changing ocean conditions.

Turbot (Scophthalmus maximus) is an important aquaculture species, but the genomic organization and expressed diversity of its antibody repertoire remain incompletely characterized. In this study, we annotated the immunoglobulin heavy chain (IGH) locus using the haplotype resolved fScoMax1.1 genome assembly, and we used this as a reference to profile the expressed turbot IgM, IgD and IgT repertoires in skin and spleen. The primary IGH locus was located on chromosome 19, spanned approximately 72 kb, and contained 25 IGHV genes, including 24 functional genes and one pseudogene, together with three IGHD, seven IGHJ and three IGHC genes corresponding to IgT, IgM and IgD. Comparison with the alternate fScoMax1.1 haplotype and a second turbot genome assembly showed conserved IGHD, IGHJ and IGHC content, whereas IGHV gene number differed among assemblies. High throughput 5RACE repertoire sequencing revealed isotype and tissue associated differences in expressed IGH diversity. IgM represented the dominant productive repertoire in both skin and spleen and showed the highest clonotypic diversity, particularly in spleen. IgD displayed an intermediate profile, whereas IgT was more enriched in skin and exhibited the strongest clonal restriction. IGHV subgroup usage was dominated by IGHV3 in IgM and IgD, whereas IgT showed a distinct profile characterized by preferential use of IGHV4, especially in skin. Gene level analysis further showed broad IGHV-IGHJ pairing in IgM and IgD, with preferential use IGHJ3 segment, while IgT sequences paired exclusively with IGHJT. Clonotype sharing between skin and spleen was isotype dependent, being strongest for IgT, intermediate for IgM, and negligible for IgD, suggesting that clonal expansion did not necessarily predict inter tissue trafficking. Together, these results provide a curated genomic and expressed repertoire framework for turbot IGH genes and reveal isotype specific organization of antibody diversity, with IgT displaying a particular repertoire pattern.

The gut microbiome is increasingly recognized as a pivotal modulator of animal behaviour, yet its influence on wild fauna remains largely unexplored. We investigated the correlational relationship between gut microbiota, behavioural phenotypes, and management practices in 26 captive endangered Iberian lynxs (Lynx pardinus) maintained within the ex-situ Iberian breeding program facilities, in two geographically distant stations in SW Spain. Behavioural observations were intensively recorded over two years, and three personality profiles emerged, i.e., (i) anomalous (with the highest frequencies for stereotypies), and (ii) sedentary and (iii) active (with the highest frequencies for sedentarism and for locomotion and surveillance, respectively). Fecal samples were analyzed for biweekly periods by 16S rRNA gene amplicon sequencing to profile bacterial composition and predicted functional pathways, and significant associations were found for each of the behavioural phenotypes. Both breeding station and local environment influenced gut microbial communities and personality profiles, underscoring the influence of management practices and local habitat in shaping the microbiome-behaviour nexus. Specific bacterial taxa and metabolic pathways were consistently associated with each behavioural phenotype, suggesting that microbial fecal signatures could serve as non invasive biomarkers for individual personality monitoring. This work constitutes the first comprehensive, multi layered examination of the interplay among behaviour, gut microbiota, and environmental factors in a large, wild carnivore. This integrative approach may help conservation programmes to optimize management decisions and improve reintroduction success

Microorganisms are the key drivers of carbon cycling in coastal marine sediment ecosystems, significantly influencing carbon storage and release during Gracilariopsis lemaneiformis cultivation. This study employed 16S rRNA sequencing, a high-throughput qPCR chip, and carbon isotope labeling to assess the impact of G. lemaneiformis cultivation on carbon cycling processes in coastal sediments. A comparative analysis was conducted between cultivated zones (GZ) of G. lemaneiformis and adjacent control zones (CZ). The results indicated that macroalgae cultivation significantly modified sediment-seawater exchange dynamics and accelerated carbon cycling within coastal marine sediment ecosystems. Furthermore, G. lemaneiformis cultivation increased the abundance of genes linked to polysaccharide degradation and carbon fixation pathways, thereby enhancing carbon cycling efficiency. The ecosystem multifunctional index, calculated based on carbon fixation gene abundance, was significantly higher in GZ compared to CZ. Incubation experiments using 13C-NaHCO3 demonstrated that cultivation markedly elevated the carbon fixation rate of sediment, emphasizing a higher potential for carbon sequestration in sedimentary environments cultivated with macroalgae. Additionally, cultivation significantly altered sediment microbial communities, simplifying their structural complexity. Key microbial taxa identified via k-core species analysis--including Subgroup10 of Desulfobacterota and MBNT15, correlated strongly with carbon fixation rates, indicating their pivotal roles in sediment carbon cycling processes. This study provides critical insights into how large-scale macroalgae cultivation influences coastal carbon dynamics and informs strategies for optimizing carbon management in aquaculture ecosystems.

Compact poultry raising has turned poultry litter into an environmental problem, as it may all be packed with heavy metals and drug-resistant germs. Of all the metals, chromium contamination not only disturbs the general environment but is also a source of concern for public health. Poultry litters were taken from 14 farms in different places, and the bacteria characters from different places were tested for their capacity to tolerate Cr(VI). A total of 31 bacterial isolates were initially screened, and three of them (AH-2, AZ-1, and AMF-3) appeared to be very resistant to chromium. The isolates were able to survive at the highest concentration, 800 mg/L of the Cr(VI); however, AH-2 was the most resistant one (MIC: 900 mg/L; MBC: 1000 mg/L). Chromium reduction tests showed that AMF-3 at high concentration showed the maximum chromium reduction, while AH-2 achieved higher chromium reduction at medium concentration. Phenotypic and biochemical analysis showed that the isolates were Staphylococcus spp., which was confirmed by 16S rRNA gene sequencing as S. cohnii, S. saprophyticus, and S. gallinarum. Moreover, chromium was detected at higher levels in poultry litter compared to the feed, with the highest accumulation in AZ farm litter (4464.0 {micro}g/kg). The highlighting feature of our article is the presence of chromium-tolerant and reducing bacteria in poultry environments. Besides that, the level of chromium in poultry litter is really high, and it points to the need for better waste management.

Lake Constance is a pre-Alpine, monomictic, oligotrophic lake situated at the southern end of Germany composed of two main water bodies: deep, oligotrophic Upper Lake Constance (ULC) and the shallow, more mesotrophic Lower Lake Constance (LLC). To date, no sequencing-based study exists of the seasonal succession of the microbial plankton in Lake Constance. Over one-year, microbial plankton communities were sampled biweekly from the top 20 m of the water column in both sites and separated into nanoplankton (NP) and picoplankton (PP). Communities were analysed using rDNA amplicon sequencing: NP samples were analysed by 18S rDNA, and PP samples by 18S and 16S rDNA sequencing. Temporal community diversity was compared between sites and the effect of two major environmental perturbations, winter vertical mixing in ULC and oxygen depletion of the bottom-water layer in LLC, on the community was examined. Despite strong environmental contrasts, microbial plankton communities exhibited conserved seasonal temporal dynamics across basins. In contrast, pronounced compositional shifts occurred during mixing and oxygen depletion events. Approximately 20% of detected taxa were positively associated with these events, with log fold changes reaching 9.82, reflecting rare or undetectable taxa outside these periods. Taxa favoured by these perturbations commonly exhibited high metabolic flexibility, including mixotrophy, fermentation, or anaerobic respiration, or possessed functional traits conferring tolerance to altered redox and mixing regimes. Our results suggest that the temporal dynamics of freshwater microbial plankton communities are driven by deterministic processes and highlight the profound impact of large, and less known, environmental changes on these communities.

Anoxia is a major stress for most vertebrates and frequently accompanies harsh winter conditions, particularly in species that spend much of the season frozen solid. North American freeze-tolerant wood frogs (Rana sylvatica) can survive several months without oxygen and endure whole-body freezing for up to eight months of the year, with [~]70% of total body water frozen as extracellular ice, yet revive when temperatures rise in spring. Survival depends on multiple adaptations, including tolerance of prolonged oxygen deprivation while frozen, when breathing and circulation are halted. A key strategy involves hepatic glycogen mobilization, producing large amounts of glucose that are distributed to tissues where it functions both as a cryoprotectant and as a substrate for anaerobic ATP production. The present study examines the role of histone lysine methylation and demethylation in regulating liver proteins under anoxic conditions. Relative protein expression of seven histone methyltransferases (ASH2L-S, ASH2L-L, RBBP5, SETD8, SMYD2, ESET, SETD1), six lysine demethylases (KDM1A, KDM3B, KDM4A, KDM4B, KDM5A, KDM5C), and eight histone marks (H3K4me1, H3K4me2, H3K9me3, H3K27me3, H3K36me3, H3K79me3, H4K20me1, H4K20me3) were evaluated in wood frog liver under control, 4-hour, and 24-hour anoxia exposures. The data indicate that histone lysine methylation and demethylation contribute significantly to transcriptional regulation under anoxia. Specifically, H3K4, H3K36, and H3K79 methylation were associated with transcriptional activation, whereas H3K9, H3K27, and H4K20 methylation correlated with transcriptional repression. These findings highlight the dynamic role of epigenetic regulation in supporting hypometabolism and stress adaptation in freeze-tolerant wood frogs.

The European flat oyster (Ostrea edulis), like numerous other oyster species, has been exploited for millennia and cultivated and translocated for centuries. Following a severe population decline, and in the context of ongoing conservation and restoration programs, genetic considerations must now be addressed to avoid mistakes. The objective of our study was to complement population genetic studies conducted at various scales along European coasts. Our sampling primarily targeted the French Atlantic, English Channel, and Mediterranean coasts, aiming to provide a fine-scale genetic characterization of populations in these regions. By integrating SNP array and low-coverage sequencing datasets, we obtained a comprehensive overview of the population genetic structure of Ostrea edulis across western Europe. Most previously identified clusters in Western Europe were confirmed. In France, populations assigned to these clusters exhibited notable within-patch homogeneity. However, two key findings emerged: (1) an extensive overlap zone between the Atlantic and western Mediterranean clusters, spanning at least from southern Portugal to southern France, and (2) the detection of a novel, clearly distinct cryptic cluster east of the English Channel, whose geographic range remains to be better delineated. These insights are critical for informing management decisions, particularly as restoration and conservation plans are currently being implemented across the species range.

RNA interference (RNAi) is a widely exploited reverse-genetics tool with potential uses for disease control. Successful RNAi has been reported in trematode-vectoring snails, but the composition of RNAi effector-encoding gene complements, a key driver for RNAi efficiency, remain unstudied in these species. Using bioinformatics and comparative genomics, we searched for orthologues of 115 RNAi effector sequences in genomes or transcriptomes of four snail vectors: Biomphalaria glabrata, B. pfeifferi, Bulinus truncatus, and Lymnaea staginalis. Gene expression patterns of selected RNAi effectors were then examined across developmental stages and tissues of the model B. glabrata snail. At least 74 RNAi-related proteins were conserved across all four species, including core components known to be essential for gene silencing. Classical systemic RNAi-deficient (SID) genes that facilitate systemic RNAi in other systems were absent, suggesting that alternative pathways may compensate for dsRNA uptake and transport. Core effectors of secondary RNAi amplification and heritable RNAi were not detected. Expressions of Dicer-1, Argonaute-2, and the exonuclease Eri-1 did not vary significantly with snail size. A putative RNAi-inhibiting Staufen orthologue showed elevated expression in the ovotestis, while another putative cholesterol-interacting gene was overexpressed in the trunk tissue and may partly contribute to RNAi import. Altogether, our results present the most comprehensive overview of RNAi pathway effectors in major intermediate snail hosts for trematodes. The findings underscore the likely broad potential for RNAi use in trematode intermediate hosts as an experimental tool and potential control method.