The bactericidal permeability-increasing protein (BPI) and lipopolysaccharide binding protein (LBP) are fundamental to innate immunity. However, their functional diversity and evolutionary conservation in ecologically crucial invertebrates, such as oysters, remain largely understudied. In this study, we identify and characterize a novel homolog of BPI/LBP, designated as ChBPI/LBP in the Hong Kong oyster (Crassostrea hongkongensis). Through structural and phylogenetic analysis, we identify ChBPI/LBP as a distinct member of the BPI protein family, with a high isoelectric point (pI of 9.26), indicating potent cationic BPI-like bactericidal function. We found that ChBPI/LBP is constitutively highly expressed at mucosal sites such as the gills and is rapidly upregulated in hemocytes following a challenge with Aeromonas hydrophila. Recombinant ChBPI/LBP demonstrated potent and specific bactericidal activity against Gram-negative pathogens. These findings suggest that ChBPI/LBP is an important antimicrobial peptide (AMP) effector in the oyster’s immune response. This work provides novel perspectives on the evolutionary mechanisms of innate immunity in bivalves and may have implications for disease management in aquaculture.

Heat Shock Proteins (HSPs) act as molecular chaperones, protecting cells by stabilizing and refolding damaged proteins under stress. While the induction of HSPs in fish under stress is well-documented, comprehensive genome-wide analyses of the entire HSP90 gene family in a comparative context remains limited. This study provides a systematic, comparative analysis of the HSP90 gene family in two economically important species with distinct thermal niches, Cyprinus carpio (common carp) and Oreochromis niloticus (Nile tilapia). Our investigation included phylogenetic relationships, motif patterns, physicochemical properties, positive selection, and expression profiles. Key findings include the identification of tandem duplications in both species and a higher number of transcription factor-binding sites (TFBSs) in tilapia compared to common carp. Positive selection analysis revealed significant evidence of adaptive evolution in the HSP90 proteins. qRT-PCR analysis revealed organ-specific responses and differing thermal tolerances, with O. niloticus exhibiting a more pronounced adaptive response to extreme heat (40 °C). These findings provide valuable insights into the evolutionary dynamics and functional divergence of the HSP90 gene family, offering a theoretical basis for understanding genetic adaptations to thermal stress. As global temperatures rise, such insights are essential for enhancing aquaculture sustainability by leveraging natural adaptive mechanisms.

The horseshoe crab Tachypleus tridentatus, listed as "Endangered" by the IUCN, is a keystone species in Asian coastal ecosystems and is critical for biomedical applications. This species currently faces multiple threats, including an emerging but overlooked hazard: botanical pesticide contamination in nursery habitats. Azadirachtin, a novel biopesticide, can trigger increased accumulation of reactive oxygen species. However, regulation of gene expression under environmental stress and their synergistic relationship with developmental processes in T. tridentatus remain unclear. We investigated the conservation implications of azadirachtin exposure in the most vulnerable life stages critical for population recruitment. Using embryonic (Stages IV-V) and first-instar larvae, we documented dose- and time-dependent mortality with heightened sensitivity in later developmental stages-periods crucial for successful recruitment. Azadirachtin induced oxidative stress through disruption of antioxidant defense systems, with rapid SOD activation (peaking at 12 h), elevated MDA levels indicating cellular damage, and biphasic T-AOC responses. Molecular analysis results revealed stage-specific expression patterns of key stress-responsive genes, including antioxidant enzymes (Mn-SOD, CAT), a Phase II detoxification enzyme (GST), and a neurotoxicity biomarker (AchE), suggesting limited adaptive capacity in early life stages. These findings challenge the assumption that plant-derived pesticides are environmentally benign and reveal a significant threat to horseshoe crab conservation. High sensitivity during embryonic development, when animals are confined to beach sediments, is particularly concerning given the overlap between agricultural runoff zones and spawning habitats. We recommend establishing pesticide-free buffer zones (minimum 500 m) around known spawning sites, implementing azadirachtin monitoring in horseshoe crab protection areas, and revising coastal pesticide regulations to account for endangered species vulnerability. Our results underscore the need to integrate emerging contaminant assessments into conservation strategies for this ecologically irreplaceable species.

Portunus pelagicus is an important marine economic species, widely distributed in coastal areas such as the Indian Ocean and the western Pacific Ocean. As a pathogenic bacterium, Vibrio parahaemolyticus poses a potential threat to marine life living in coastal areas. As key regulatory factors in the process of apoptosis, p53, Bax, Caspase-3 and AIF genes play an important role in removing infected cells and inhibiting the spread of pathogens. This study evaluated the acute toxicity, tissue damage, and induced apoptosis of V. parahaemolyticus infection in P. pelagicus through physiological and molecular responses, and analyzed the expression spectrum of p53, Bax, Caspase-3, and AIF genes. The results showed that the 48 h LD50 of V. parahaemolyticus infection in P. pelagicus was 1.72 × 107 CFU/mL. The toxic effect of this bacterium significantly affected the tissue morphology and apoptosis levels of P. pelagicus hepatopancreas and gill tissues. Through RT-PCR, p53, Bax, Caspase-3, and AIF genes were successfully cloned, with open reading frames (ORFs) of 885, 1509, 1074, and 1323 bp, respectively. Through RT-qPCR, it was found that p53, Bax, Caspase-3, and AIF genes were expressed in the stomach, epidermis, hepatopancreas, gill, heart, intestine, muscle, and eyes tissues. Among these, expression levels in the hepatopancreas and gill tissues were notably higher. Overall, V. parahaemolyticus activates immune responses in P. pelagicus, causing tissue structural damage and elevating apoptosis levels, thereby compromising normal growth and health.

Crassostrea hongkongensis is an economically important shellfish in coastal areas of the South China Sea. In recent years, large numbers of oysters have often died during high-salinity seasons, and this has caused serious economic losses to the oyster industry. Betaine is an important osmotic regulator that has osmoprotective effects in many aquatic animals. Here, we found that the survival rate of oysters could be increased by 58.33 % under a salinity of 35 %o by adding exogenous betaine. We cloned and analyzed ChCDH (choline dehydrogenase), ChBADH (betaine aldehyde dehydrogenase), and ChBHMT (betaine homocysteine methyltransferase) in C. hongkongensis, and characterized their structures and expression patterns. We used RNAi technology to interfere with the mRNA expression of ChBADH to clarify the molecular mechanism underlying the role of betaine in the osmoregulation of C. hongkongensis. We found that the expression of ChBADH and ChBHMT significantly decreased and the expression of ChCDH significantly increased from 0 h to 48 h under a salinity of 35 %o. The activities of ChCDH, ChBADH, and ChBHMT fluctuated after the expression of ChBADH was altered, but no significant differences in the expression of these enzymes were observed between groups (P > 0.05). Interference of ChBADH expression led to a significant decrease in the betaine content and the survival of oysters at 72 h, which indicated that oysters regulate the intracellular betaine content through the expression of ChCDH, ChBADH, and ChBHMT to maintain a stable osmotic pressure under high-salinity conditions. The results provide new insights into the mechanism of high-salt adaptation in oysters.

Metamorphosis, the crucial transition from planktonic to sessile life stages, marks a key developmental milestone in marine bivalves, particularly for commercially valuable species like Lutraria sieboldii. We conducted a comprehensive transcriptomic analysis using RNA sequencing (RNA-seq) during the larval settlement stage to elucidate the molecular mechanisms underlying this ecologically and economically significant process. Our study generated 89.64 Gb of high-quality clean data (≥6.20 Gb per sample, Q30 ≥ 92.7 %), ensuring robust and reliable insights into gene expression dynamics. Through weighted gene co-expression network analysis (WGCNA), we identified the turquoise module as a key regulatory network strongly associated with settlement-related traits. This module was significantly enriched in critical biological processes, including mRNA splicing via spliceosome, pathways related to cytoskeletal organization and calcium signaling, and C-type lectin receptor signaling, which are crucial for substrate interaction and tissue remodeling. Notably, hub genes within this module included essential components of the spliceosome (SF3B1, RBM8A), calcium signaling regulators (CALM3), and cytoskeletal modulators (ACTB, MFAP1). Furthermore, transcriptional profiling revealed a significant upregulation of genes involved in inorganic ion transport and metabolism, cytoskeletal dynamics, protein turnover, and energy production. These results offer strong evidence for the coordinated regulation of molecular mechanisms during substrate recognition and tissue restructuring in L. sieboldii metamorphosis. As the first comprehensive transcriptomic resource describing larval settlement in this species, our study advances our understanding of conserved developmental pathways and suggests potential aquaculture strategies, such as optimizing calcium signaling or spliceosome activity to enhance larval settlement efficiency in hatchery settings.

Nile tilapia has become one the most significant species in global aquaculture due to its exceptional adaptability, rapid growth and high reproductive capacity. Role of Sox genes in reproduction and development made attention to further investigate the role of these genes. Based on N. tilapia importance in aquaculture industry and role of Sox genes in the development of tissues and organs during embryogenesis, this study systematically analyzed Sox genes functionality in N. tilapia by using computational tools. In our study, phylogenetic analysis revealed that N. tilapia is most closely related to blue tilapia compared to other species. Sox genes are conserved in nature and share both acidic and basic properties as well as thermostable and hydrophobic in nature. The subcellular localization in N. tilapia indicated that majority of the Sox proteins are expressed in the Nucleus and Cytoplasm. Enrichment analysis explains the Sox genes' role in cell differentiation, and biosynthesis process and acts as a molecular functional regulator. Significant differences in transcription binding sites were observed, highlighting the potential role of these regulatory regions in the regulation of Sox genes in N. tilapia. First time it is reported that Sox genes in N. tilapia have four major recombinant breakpoints that revealed phylogenetic segregation across several recombination fragments. In this primer, we aim to provide the reader with a comprehensive overview of Sox gene family in N. tilapia and to provide the functional properties of Sox genes for better follow-up in upcoming experiments for futuristic research.

Tachypleus tridentatus is a rare and endangered marine organism with considerable scientific and economic value. It has existed on Earth for about 450 million years and its continuation to the present day may be related to its unique immune system. Owing to its drastic population decline, diverse technical approaches are required for its recovery, and the development and growth of its larvae are crucial in this context. Vibrio parahaemolyticus is a common marine pathogen that impairs the healthy growth of marine organisms. The peak period of V. parahaemolyticus occurrence is from May to November, which significantly overlaps with the T. tridentatus spawning period from April to September. However, the response mechanisms of juvenile T. tridentatus to V. parahaemolyticus stress remain unknown. Hence, in this study, we aimed to investigate these response mechanisms through acute toxicity assays, histological observations, and transcriptome analysis. The results showed that the 48 h LD50 of V. parahaemolyticus-infected T. tridentatus larvae was determined to be 1.31 × 108 CFU/g. Histological analysis showed that V. parahaemolyticus damaged the larval tissue. In addition, RNA sequencing (RNA-Seq) identified 2347 differentially expressed genes (DEGs; 1440 upregulated and 907 downregulated genes) and 243 enriched signaling pathways. Functional enrichment analysis revealed the enrichment of immunoregulatory pathways, including the Wnt signaling pathway, ECM-receptor interaction, aminoacyl-tRNA biosynthesis, and Toll and Imd signaling pathways. Seventeen DEGs were randomly selected for real-time RT-PCR (RT-qPCR) validation, and their expression patterns were consistent with those obtained via RNA-Seq. The study of the response mechanism of T. tridentatus larvae to V. parahaemolyticus stress provides scientific references for the protection of T. tridentatus habitats and the recovery of its population size.

Escherichia coli and Salmonella are significant foodborne zoonotic pathogens, causing serious human illness. The rising global prevalence of antimicrobial resistance (AMR) in these species exacerbates their public health risk, complicating the treatment of bacterial infection. This study investigates its prevalence, resistant genes, and treatment strategy against antibiotic-resistant bacteria, focusing on E. coli and Salmonella isolates from Nile tilapia. Prevalence of E. coli and Salmonella was found to be 32 and 22% respectively. Antibiotic susceptibility testing revealed resistance to five antibiotics in E. coli and four in Salmonella. Physiochemical properties of antibiotic resistance genes (ABRGs) indicated that the TetB gene has the highest aliphatic index in both bacteria, suggesting greater stability. All Bla proteins were hydrophobic as indicated by negative GRAVY values, which may contribute to antibiotic efflux or modification of antibiotic targets. Motif analysis identified functional domains, and cellular localization prediction showed that TetA and TetB genes are primarily expressed in the cell membrane. To combat this resistance, a checkerboard method was used to explore novel antibiotic combinations. For E. coli, one synergistic and two additive combinations were identified, while for Salmonella, two synergistic and one additive combination were effective. These results highlight the importance of regularly evaluating antibiotic combinations to combat resistance and preserve antibiotic efficacy.

Introduction:Rumen microbiota and host metabolites play a key role in regulating ruminant production performance and physiological adaptation. However, the interplay between host physiological status and rumen microbial-metabolite dynamics across lactation stages in buffaloes remains unclear. Methods:This study employed a multi-omics approach, integrating metagenomic and serum metabolomic analyses, to investigate microbial remodeling and metabolic adaptations in buffaloes during lactation and dry periods. Results:Metagenomic analysis revealed increased abundances of Anaerovibrio, Succiniclasticum, and Methanobrevibacter_A during lactation, associated with lipid hydrolysis, propionate production, and methanogenesis, respectively. Glycoside hydrolase families GH2, GH3, GH5, and GH13 were enriched, indicating elevated carbohydrate degradation potential. In contrast, Butyrivibrio, Fibrobacter, and Eubacterium_Q were predominant during the dry period, contributing to fiber degradation and butyrate synthesis. Functional pathways related to niacin metabolism, bicarbonate reabsorption, and neuroactive ligand-receptor interaction were significantly upregulated during lactation. Metabolomic profiling identified lactation-enriched metabolites such as indole-3-methylacetate, D-maltose, and gluconic acid, correlating with immune and metabolic indicators (e.g., IgA, glucose, LDL). Conversely, dry period metabolites such as 1-methylhistidine and 5-hydroxyindoleacetic acid indicated physiological shifts toward tissue repair and stress mitigation. Discussion:The integrative analysis revealed that host physiological demands during lactation coordinate rumen microbial restructuring to enhance triglyceride degradation, fatty acid biosynthesis, and energy mobilization, thereby supporting milk production. These findings provide novel insights into the host-driven microbiome-metabolite axis underlying lactation in buffaloes.

Buffaloes are mono-ovulating animals, with only about 5% of primordial follicles being fully capable of maturation into primary oocytes throughout their reproductive years. In vitro primordial follicle activation technology provides a new way to manipulate and utilize oocyte resources. However, in vitro activation of buffalo primordial follicles has not been reported. In this study, buffalo cortical strips were cultured in vitro and activated with PI3K and mTOR stimulators, and the proportion of activated and developed follicles was evaluated and compared between groups . Furthermore, the key genes involved in primordial follicle activation were screened using RNA sequencing. Results showed that buffalo ovarian cortex can be well preserved by being cultured in vitro for at least 7 days and maintain its tissue properties and follicular morphology. In vitro, treatment with PI3K and mTOR pathway stimulators significantly enhanced the activation efficiency of the primordial follicles. In addition, several differentially expressed genes related to follicular development, such as IDO1, CXCL10 and CXCL6 were significantly up-regulated after stimulation. Our findings demonstrate that PI3K and mTOR stimulators can significantly promote the activation and development of buffalo follicles, and providing technical support and a theoretical basis for the optimization of in vitro culture technology of buffalo preantral follicles .

Mauremys mutica is a widely cultured pond turtle in China that can hold its breath underwater for up to 7 h. However, the adaptive mechanism of this hypoxia-resistant phenotype remains unknown. In the present study, no M. mutica died until 6 h of hypoxic stress. Inflammation was observed in the lungs of dead individuals along with a lung cell apoptosis rate of 12.3% in the death group, which was about six times that of the survival group. Transcriptome sequencing produced 379,659,748 clean reads, and 38,981 genes were obtained. A total of 1566, 1555 and 756 differentially expressed genes (DEGs) were detected between the survival group and the death group, the survival group and the control group, and the death group and the control group, respectively. And the DEGs were enriched in the inflammation, apoptosis, sugar transport, antioxidant, fructose, and mannose metabolism, arginine and proline metabolism, glycosaminoglycan biosynthesis, P53, and MAPK signaling pathways. This study offers new insight into the molecular mechanisms occurring in the lungs of M. mutica during acute hypoxia, which may facilitate genetic selection for hypoxia-resistant lines in M. mutica.

Microcystin-LR (MC-LR), a cyanobacterial toxin, poses a considerable threat to aquatic organisms. Herein, we focused on the economically important crustacean Eriocheir hepuensis to examine the acute toxic effects of MC-LR stress and its molecular mechanisms. The half-lethal concentration (LD50) of MC-LR for the E. hepuensis was determined to be 64.78 μg/kg, with a calculated safety concentration of 6.48 μg/kg through a 96-h acute toxicity test (n = 240). Exposure to a sublethal concentration (60 μg/kg) for 48 h resulted in 56.7 % survival rate (n = 60) and caused substantial hepatopancreatic pathological damage, including cell vacuolation, chromatin condensation, and mitochondrial fragmentation. To elucidate the underlying mechanisms, further cloning and identification of the apoptosis-related genes p53 (open reading frame (ORF 1284 bp), Bax (ORF 1482 bp), and Bcl-2 (ORF 732 bp) showed that their expression levels were the highest in the hepatopancreas (2.9, 3.7, and 3.5 times that of the control group, respectively). Time-series analysis further showed that the p53 and Bax gene expression rapidly increased at stress onset but gradually declined, whereas the Bcl-2 gene expression was temporarily downregulated, and a substantial negative correlation was observed with Bax expression. These molecular dynamics reveal that MC-LR-induced hepatopancreatic damage and mortality in E. hepuensis are mediated through coordinated apoptotic gene regulation, with the p53-Bax-Bcl2 pathway orchestrating the cellular stress response. This study providing crucial scientific insights into the molecular responses of crustaceans to algal toxins.

Zinc is an essential micronutrient in fish that plays vital role in many biological functions. Optimal Zinc level is indispensable in fish feed due to its multifaceted roles specifically in growth, antioxidant capacity and overall aquaculture productivity. The impact of dietary supplementation with zinc methionine (ZM), zinc oxide nanoparticles (ZNPs) and zinc sulfate (ZS) was assessed in juvenile Cyprinus carpio. Fish were fed a basal diet (Control), ZM, ZNPs, and ZS based diets at levels of 10, 20, 30, and 40 mg/kg for 90 days. ZNPs at 20 mg/kg exhibited the maximum weight gain (137.46 +/- 1.74 %) and specific growth rate (1.44 +/- 0.01 %/day), with lowest feed conversion ratio (1.75 +/- 0.021) compared to the ZM and ZS diet groups. Fish fed 20 mg/kg ZNPs showed significantly higher superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) activity, along with reduced liver thiobarbituric acid reactive substances (TBARS). Glucose level was lower in ZNPs groups as compared to other zinc sources, while cortisol levels decreased dose-dependently (p < 0.001). The highest protein level was observed in fish fed 20 mg/kg ZNPs. Serum and muscle zinc concentrations increased in dose dependent manner in the all zinc supplemented dietary groups. Optimal dietary zinc levels were identified for ZM (30.95-35.29 mg/kg), ZNPs (24.13-27.70 mg/kg), and ZS (30.15-33.37 mg/kg) based on growth and health markers. In conclusion, ZNPs improved growth performance, antioxidant capacity, and overall health in C. carpio, making it a promising alternative to traditional zinc supplements.

Staphylococcus aureus is a major food-borne opportunistic pathogen that poses a significant public health threat, leading to severe tissue infections, bacteremia, and often life-threatening illness. While S. aureus has been extensively studied in livestock and poultry products in China, there is a notable lack of data regarding its presence and characteristics in aquatic products. This study investigates the prevalence, antibiotic resistance (ABR), its molecular profiling, and treatment regimens of S. aureus isolates from Oreochromis niloticus (Nile tilapia). A total of 300 tilapia samples from various fish markets showed an overall S. aureus prevalence of 31.67 %. ABR profiles revealed significant resistance to commonly used antibiotics, such as amoxicillin/clavulanic acid (65 %) and tetracycline (55 %), highlighting the widespread emergence of resistance. Phylogenetic analysis revealed strong clade support for resistance gene clusters, such as MecA/C, ErmA, and TetK. Motif analysis showed distinct motifs, indicating their role in ABR mechanisms. Physiochemical properties showed that β-lactams and macrolides have a hydrophilic nature, and the tetracycline class exhibited a hydrophobic nature. BlaZ and MecA exhibit the highest occurrence of GATA, potentially emphasizing the regulation by transcription factors in the resistance to β-lactams group, while TEM exhibited a high frequency of GATA, YY1, and OCT1, implying these factors may regulate β-lactamase production. Through synergy evolution, one synergistic and three additive interactions were identified, indicating its potential for novel combination therapies against multidrug-resistant (MDR) pathogens. Our study findings underscore the severity of ABR in aquaculture, highlighting the importance of effective antibiotic strategies. The comparative analysis of treatment efficacy also highlights the need for alternative strategies to control bacterial infections. Overall, our work offers valuable insights into resistance mechanisms and future management approaches for combating MDR pathogens in aquaculture settings.

The Fibroblast Growth Factor (FGF) gene family of Nile tilapia plays a central role in environmental adaptation and aquaculture resilience. This study integrated in silico analyses and molecular docking to comprehensively analyze the FGF gene family in Nile tilapia. Phylogenetic reconstruction identified three clades (A-C): In Group A, the subclade of genes (FGF19/21/23) revealed conserved endocrine and metabolic roles. Group B genes (FGF7/8a/8b/17/18/24) retained ancestral development functions linked to teleost-specific genome duplication. In Group C, the subclade of genes (FGF1/2/5) exhibiting sub-functionalization, such as FGF2 wound healing versus FGF5 mitogenic roles. The structural analysis highlighted the conserved β-trefoil domain, critical for receptor binding, alongside lineage-specific innovation like heparin-binding motifs in FGF. Physicochemical properties observed a high aliphatic index (AI) of 101.68 in FGF19, which is crucial for climate adaptation. Molecular docking revealed novel predicted interactions, such as FGF4/17 with androgen receptor (AR), potentially influencing male reproduction, while KLF5/DDBI binding expanded FGF roles to gill regeneration and oxidative damage mitigation. Glucocorticoid (GR) exhibited the most potent predicted interaction with a high docking score (− 233.99 to − 313.15), particularly for FGF4 (− 310.86), and FGF8a (− 313.15), suggesting conserved GR-mediated regulation for metabolism, inflammation, and tissue repair. This study pioneers the exploration of potential cross-talk between FGF proteins and nuclear receptors, and provides insights into the link between FGF structural evolution and aquaculture resilience. By bridging genomic features and environmental adaptation, this research contributes to a better understanding of Nile tilapia’s potential as a model for sustainable aquaculture.

IntroductionThe buffalo is an important domestic animal globally, providing milk, meat, and labor to more than 2 billion people in 67 countries. The rumen microorganisms of buffaloes play an indispensable role in enabling the healthy functionality and digestive function of buffalo organisms. Currently, there is a lack of clarity regarding the differences in the composition and function of rumen microorganisms among buffaloes at different growth stages.MethodsIn this study, metagenomics sequencing technology was applied to examine the compositional and functional differences of rumen microorganisms in adult and breastfed buffaloes.ResultsThe results revealed that the rumen of adult buffaloes had significantly higher levels of the following dominant genera: Prevotella, UBA1711, RF16, Saccharofermentans, F23-D06, UBA1777, RUG472, and Methanobrevibacter_A. Interestingly, the dominant genera specific to the rumen of adult buffaloes showed a significant positive correlation (correlation>0.5, p-value<0.05) with both lignocellulose degradation-related carbohydrate-active enzymes (CAZymes) and immune signaling pathways activated by antigenic stimulation. The rumen of breastfed buffaloes had significantly higher levels of the following dominant genera: UBA629, CAG- 791, Selenomonas_C, Treponema_D, Succinivibrio, and RC9. Simultaneously, the rumen-dominant genera specific to breastfed buffaloes were significantly positively correlated (correlation>0.5, p-value<0.05) with CAZymes associated with lactose degradation, amino acid synthesis pathways, and antibiotic-producing pathways.DiscussionThis indicates that rumen microorganisms in adult buffaloes are more engaged in lignocellulose degradation, whereas rumen microorganisms in breastfed buffaloes are more involved in lactose and amino acid degradation, as well as antibiotic production. In conclusion, these findings suggest a close relationship between differences in rumen microbes and the survival needs of buffaloes at different growth stages.

Sodium dichloroisocyanurate (NaDCC, C3Cl2N3NaO3) is a solid chlorine-containing product that is widely used as a disinfectant in living environments, which has potential toxic effects on human and rats. Phascolosoma esculenta is a species native to the southeast coast of China and can be used as an indicator organism. In the present study, 150 P. esculenta were used to determine the LC50 of NaDCC for P. esculenta, then 100 P. esculenta were used to analysis the change of histopathology, oxidative stress and transcriptome after NaDCC exposure. The results showed that the LC50 of NaDCC for 48 h was 50 mg/L. NaDCC stress induced pathological events in P. esculenta, including blisters, intestinal structural damage and epithelial cell ruptured or even loss. The highest and lowest intestinal activity of superoxide dismutase in individual survivors was detected at 12 h and 72 h, respectively. Malondialdehyde levels in the intestine declined gradually from 3 h and increased at 9 h, and peaked at 12 h. Total antioxidant capacity declined at 3 h and dropped below the levels of control group after 9 h. Transcriptome sequencing analysis yielded a total of 48.65 Gb of clean data. A total of 34,759 new genes were found including 957 differentially expressed genes (DEGs). The DEGs were significantly enriched in ferroptosis, response to chemicals, response to stress, immune system, ion transport, cell death, oxidation-reduction, cellular homeostasis, protein ubiquitination, and protein neddylation. Additionally, the levels of detoxification enzymes, such as glutathione-S-transferase, cytochrome P450, ABC, UDP-glycosyltransferase and SLC transporters of endogenous and exogenous solutes were significantly changed. Overall, the results provide reference for reasonable use of disinfectants during farming, and also provide insight into the mechanisms related to NaDCC toxicity in P. esculenta.

Background Tapes dorsatus is an economically important benthic animal in the Beibu Gulf of China. However, the deficiency of microsatellite markers has hindered the study of its genetics. The development of microsatellite markers will provide useful tools for genetic improvement, variety identification, phylogenetic analysis and resource conservation. Methods and results Within the genome sequence, 145,008 simple sequence repeats (SSRs) were identified, and 29,691 primer pairs were designed successfully. A total of 100 primer pairs were randomly synthesized for testing, and 93 primers yielded products. Sixty highly polymorphic primers were used to reveal the genetic diversity of 50 T. dorsatus individuals. The average number of alleles ( Na ) of the population was 10.40; the average number of effective alleles was 6.16, the average expected heterozygosity ( He ) was 0.82, and the average polymorphic information content was 0.80. The genetic structure of the population was detected, by which the population could be divided into three subpopulations. Conclusion We identified 145,008 SSRs in the genome of T. dorsatus and designed 29,691 primer pairs in this study. Of 100 synthesized primers, 60 were highly polymorphic and used to reveal the genetic diversity and structure of the population. The SSR markers identified here will provide useful tools and a foundation for genetic diversity, linkage mapping and molecular marker-aided breeding in T. dorsatus .

The Hong Kong oyster, Crassostrea hongkongensis, is a significant bivalve species with economic importance. It primarily inhabits the estuarine intertidal zones in southern China, making it susceptible to salinity fluctuations. Consequently, investigating the molecular mechanisms governing salinity regulation in C. hongkongensis is essential. In this study, we conducted miRNA-seq on C. hongkongensis to compare miRNA expression differences under varying salinities (5‰, 25‰, and 35‰). The miRNA sequencing revealed 51 known miRNAs and 95 novel miRNAs across nine small RNA libraries (S5, S25, and S35). Among these miRNAs, we identified 6 down-regulated differentially expressed (DE) miRNAs in response to hypo-salinity stress (5‰), while 1 up-regulated DE miRNA and 5 down-regulated DE miRNAs were associated with hyper-salinity stress (35‰). Additionally, we predicted 931 and 768 potential target genes for hypo- and hyper-salinity stress, respectively. Functional gene annotation indicated that the target genes under hypo-salinity stress were linked to vesicle-mediated transport and metal ion binding. Conversely, those under hyper-salinity stress were primarily involved in signal transduction and metabolic processes. These findings have provided insights into the regulatory role of miRNAs, their potential target genes and associated pathways in oyster hypo- and hyper-salinity stress, which establish a foundation for future studies on the roles of miRNAs in salinity acclimation mechanisms in C. hongkongensis.