Effects of different salinity reduction intervals on osmoregulation, anti-oxidation and apoptosis of Eriocheir sinensis megalopa.

Eriocheir sinensis megalopa has a special life history of migrating from seawater to freshwater. In order to investigate how the megalopa adapt themselves to the freshwater environment, we designed an experiment to reduce the salinity of water from 30 ppt to 0 at rates of 30 ppt, 15 ppt, 10 ppt, and 5 ppt per 24 h to evaluate the effects of different degrees of hyposaline stress on the osmotic regulation ability and antioxidant system of the megalopa. Experimental results related to osmotic pressure regulation show that the gill tissue of megalopa in the treatment group of 30 ppt/24 h rapid reduction of salinity was damaged, while in the treatment group of 5 ppt/24 h it was intact. At the same time, the experiment also found that in each treatment group with different salinity reduction rates, compared with the control salinity, the NKA activity of megalopa increased significantly after the salinity was reduced to 20 ppt (p < 0.05). In addition, two genes involved in chloride ion transmembrane absorption have different expression patterns in the treatment groups with different salinity reduction rates. Among them, Clcn2 was significantly highly expressed only in the rapid salinity reduction intervals of 30 ppt/24 h and 15 ppt/24 h (p < 0.05). Slc26a6 was significantly highly expressed only in the slow salinity reduction intervals of 10 ppt/24 h and 5 ppt/24 h (p < 0.05). On the other hand, the results of antioxidant and apoptosis related experiments showed that in all treatment groups with different rates of salinity reduction, the activities of T-AOC, GSH-PX, and CAT basically increased significantly after salinity reduction compared to the control salinity. Moreover, the activities of T-AOC and CAT were significantly higher in the 10 ppt/24 h and 5 ppt/24 h treatment groups than in the 30 ppt/24 h and 15 ppt/24 h treatment groups. Finally, the experimental results related to apoptosis showed that the expression trends of Capase3 and Bax-2 were basically the same in the treatment groups with different salinity reduction rates, and their expressions were significantly higher in the 10 ppt/24 h and 5 ppt/24 h treatment groups than in the 30 ppt/24 h and 15 ppt/24 h treatment groups. In summary, the present study found that megalopa had strong hyposaline tolerance and were able to regulate osmolality at different rates of salinity reduction, but the antioxidant capacity differed significantly between treatment groups, with rapid salinity reduction leading to oxidative damage in the anterior gills and reduced antioxidant enzyme activity and apoptosis levels.

Effects of Different Sources of Culture Substrate on the Growth and Immune Performance of the Red Swamp Crayfish (Procambarus clarkii).

The substrate in the aquatic environment plays a crucial role in nutrient deposition and recovery for the growth of aquatic organisms. In order to optimize the culture medium of Procambarus Clarkii, culture media from different sources were selected in this study to explore their effects on the growth and immune performance of red swamp crayfish. The results showed that the weight gain rate (WGR), body length growth rate (BLGR) and specific growth rate (SGR) in group I2 were the highest, followed by group I1 and group I3. The WGR and SGR of crayfish in the I1 and I2 groups were significantly higher than those in the I3 group (p < 0.05). The activities of acid phosphatase (ACP), alkaline phosphatase (AKP) and superoxide dismutase (SOD) were the highest in group I2, followed by group I3, and the lowest in group I1. The expression trends in growth-related genes, nuclear hormone receptor (E75), molt-inhibiting hormone (MIH) and chitinase genes were similar, and the expression levels in the I2 group were higher than those in the I1 and I3 groups. It was noted that the expression levels of E75 and MIH genes in the I2 group were significantly higher than those in the I3 group (p < 0.05). α diversity analysis of 16S rRNA data showed that there was no statistically significant difference in the abundance of intestinal flora among the three culture substrate groups. The ß diversity in the Xitangni group, crayfish Tangni group and Shuitangni group was significantly different. These changes in microbiota suggest that using different substrates to culture crayfish leads to differences in gut microbiota diversity. To sum up, the growth in crayfish and immune performance influenced by the culture substrate condition and aquatic breeding sediment substrates, rather than crab pool and paddy field pond sediment substrates, showed a better effect.

Changes in aggression and locomotor behaviors in response to zinc is accompanied by brain cell heterogeneity and metabolic and circadian dysregulation of the brain-liver axis.

Zinc is an essential nutrient for life, but over-accumulation can result in toxicity. Anthropogenic activities can increase zinc concentrations in aquatic environments (e.g., to ∼0.46-1.00 mg/L), which are above the safe level of 0.1 mg/L. We investigated the behavior and physiology of zebrafish (Danio rerio) in response to environment-related exposure to zinc chloride at 0.0 (Ctrl), 1.0 (ZnCl2-low) and 1.5 (ZnCl2-high) mg/L for 6 weeks (the zinc conversion ratio of zinc chloride is ∼0.48 and the nominal (measured) values were: Ctrl, 0 (∼0.01); ZnCl2-low, 0.48 (∼0.51); ZnCl2-high, 0.72 (∼0.69) mg/L). Low-zinc exposure resulted in significantly increased locomotion and fast moving behaviors, while high-zinc exposure resulted in significantly increased aggression and freezing frequency. Single cell RNA-seq of neurons, astrocytes, and oligodendrocytes of the brain revealed expression of genes related to ion transport, neuron generation, and immunomodulation that were heterogeneously regulated by zinc exposure. Astrocyte-induced central nervous system inflammation potentially integrated neurotoxicity and behavior. Integrated analyses of brain and hepatic transcriptional signatures showed that genes (and pathways) dysregulated by zinc were associated with sensory functions, circadian rhythm, glucose and lipid metabolism, and amyloid ß-protein clearance. Our results showed that environment-related zinc contamination can be heterogeneously toxic to brain cells and can disturb coordination of brain-liver physiology. This may disrupt neurobehavior and cause a neurodegeneration-like syndrome in adult zebrafish.

Dynamic changes in microbial community structure in farming pond water and their effect on the intestinal microbial community profile in juvenile common carp (Cyprinus carpio L.).

Water quality parameter dynamics, gut, sediment and water bacteria communities were studied to understand the environmental influence on the gut microbial community of a new strain of Huanghe common carp. A total of 3,384,078 raw tags and 5105 OTUs were obtained for the gut, water and sediment bacteria. The water quality had a stronger influence on the water bacteria community than gut and sediment bacteria communities. The ambient water quality parameters also significantly influenced the water and sediment bacteria communities. Comparing the gut, sediment, and water microbial communities, a relationship was found among them. However, gut bacteria were more closely related to sediment bacterial communities than to water bacteria communities. The results showed that the top three bacterial taxa were identical in gut and sediment samples in the early days of rearing. Interestingly, bacterial communities in the carp gut, water, and sediment had different adaptabilities to variations in environmental factors.

Identification, expression and pro-inflammatory effect of interleukin-17 N in common carp (Cyprinus carpio L.).

Two interleukin (IL)-17 N genes (CcIL-17Na and b) present on different linkage groups were identified in the common carp (Cyprinus carpio) genome and confirmed by polymerase chain reaction (PCR) and real time (RT)-PCR in this experiment. Synteny analysis revealed that IL-17 N is transcribed by the complement sequence of TOP3B's intron 2. It is flanked by SDF2L and PPM1F in all fish studied to date, except fugu (Takifugu rubripes). The open reading frames of the two CcIL-17Ns are 411 base pairs long and encode 136 amino acids. The amino acid identity/similarity between CcIL-17Na and b is 91.2%/97.1%. The CcIL-17Ns share identity (46.8-90.4%) with their orthologs from other teleosts. Identities/similarities to other members of the IL-17 family in common carp were low at 21.4-30.2%/31.4-51.4%. In the phylogenetic tree, IL-17Ns from spotted gar (Lepisosteus oculatus, the ancestor of teleosts) and coelacanth (Latimeria chalumnae, the ancestor of tetrapods) were grouped within the same branch with a high bootstrap value of 97%, which indicates that IL-17 N is an ancient and conserved gene. Quantitative RT-PCR results showed that CcIL-17Ns were most highly expressed in the brain of healthy individuals. The expression in brain was significantly induced at 6 h post Aeromonas hydrophila infection; at 1 day post infection, expression in liver, muscle, skin, spleen, and head kidney was up-regulated. In addition, the upregulated expression of proinflammatory cytokines IL-1ß, IFN-γ, IL-6, chemokine CCL20, NF - κ B and TRAF6 in kidney tissue by ccIL-17 N recombinant protein also indicate that IL-17 N can promote inflammation through NF-κB pathway and induce the expression of chemokines and inflammatory factors.

Molecular insights into information processing and developmental and immune regulation of Eriocheir sinensis megalopa under hyposaline stress.

Eriocheir sinensis is an important euryhaline catadromous crustacean of the Yangtze River and an important commercial species for breeding in China. However, wild E. sinensis have suffered serious damage attributed to overfishing, climate change, etc. The Ministry of Agriculture of China issued a notice banning the commercial fishing of wild E. sinensis. E. sinensis megalopa migrates upriver into fresh water for growth and fattening, which creates optimal conditions to experimentally explore its hyposaline osmoregulation mechanism. We performed comparative transcriptome analyses of E. sinensis megalopae under hyposaline stress. The results suggest that KEGG pathways and genes related to genetic information processing, developmental regulation, immune and anti-stress responses were differentially expressed. The present study reveals the most significantly enriched pathways and functional gene groups, and explores the hyposaline osmoregulation mode of E. sinensis megalopae. This study lays a theoretical foundation for further studies on the osmoregulation and developmental mechanisms of E. sinensis.

Molecular insights into the sex-differential regulation of signal transduction in the cerebral ganglion and metabolism in the hepatopancreas of Eriocheir sinensis during reproduction.

The Chinese mitten crab (Eriocheir sinensis), an economically valuable crustacean that is popular for its flavor, exhibits catadromous spawning migration. Overfishing and environmental pollution have inflicted serious damage on wild E. sinensis populations, and the Chinese government has banned the commercial fishing of this species in the Yangtze River. Studies have examined the sexual dimorphism in the body size and morphology of crabs, but there are few reports on the molecular regulatory mechanisms that occur during the reproduction of E. sinensis. In this study, we performed the first comparative transcriptome analyses of the cerebral ganglion and hepatopancreas of E. sinensis during reproduction. The results indicate that E. sinensis has significant sexual dimorphism in signal transduction, metabolism, substance transportation, and cellular protection. This study aims to provide information that can be used as a basis for further research on the molecular mechanisms that underlie sexual dimorphism in E. sinensis during reproduction. Furthermore, the results can be used to support the development of the E. sinensis breeding industry and the restoration of wild E. sinensis.

Identification, expression and enzyme activity of the group III sPLA2 s in Cyprinus carpio L.

Five group III secreted phospholipase (pla2g3s) homologous genes located on different linkage groups were identified from common carp (Cyprinus carpio), which we named Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3b, Ccpla2g3c1 and Ccpla2g3c2. The five genes encode 530, 525, 461, 752 and 753 amino acids, respectively. Sequence analysis showed that the Ccpla2g3as contain seven exons and the others contain four exons. Synteny analysis of fish pla2g3s indicated that pla2g3a and pla2g3b were from the same ancestor gene, and Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3c1 and Ccpla2g3c2 were from the specific genome duplication of common carp. Due to the significant variation of the pla2g3bs from common carp and zebrafish (Danio rerio), they formed a separate group in the phylogenetic tree. The tissue distributions of Ccpla2g3s coincided with their expression profiles during the embryo stages. The expression levels of Ccpla2g3as and Ccpla2g3cs were low at the embryo stages, and they were abundant in the liver and brain, respectively, whereas the expression of Ccpla2g3b was high at 0.5 h after fertilization and in the ovary. We obtained three soluble recombinant proteins of the bee venom-like PLA2 (BVLP) from Ccpla2g3 and evaluated their PLA2 enzyme properties. The optimum pHs of MBP-a1-BVLP, MBP-b-BVLP and MBP-c1-BVLP were 7.5, 7.0 and 8.0, respectively, and specific activities were 7.68 ± 0.66, 4.155 ± 0.158 and 1.93 ± 0.05 U µmol-1 , respectively. The Kd for Ca2+ of MBP-b-BVLP was the lowest (2.6 µM), whereas the values for both MBP-a1-BVLP and MBP-c1-BVLP were about 15 µM. The Km values of three proteins ranged from 31.9 to 41.91 µM.

Transcriptome analysis of the brain provides insights into the regulatory mechanism for Coilia nasus migration.

BACKGROUND: Coilia nasus (C. nasus) is an important anadromous fish species that resides in the Yangtze River of China, and has high ecological and economical value. However, wild resources have suffered from a serious reduction in population, attributed to the over-construction of water conservancy projects, overfishing, and environmental pollution. The Ministry of Agriculture and Rural Affairs of the People's Republic of China has issued a notice banning the commercial fishing of wild C. nasus in the Yangtze River. Wild C. nasus populations urgently need to recover. A better understanding of C. nasus migration patterns is necessary to maximize the efficiency of conservation efforts. Juvenile C. nasus experience a simultaneous effect of increasing salinity and cold stress during seaward migration, and the brain plays a comprehensive regulatory role during this process. Therefore, to explore the early seaward migration regulation mechanism of juvenile C. nasus, we performed a comparative transcriptome analysis on the brain of juvenile C. nasus under salinity and cold stress simultaneously. RESULTS: Relevant neurotransmitters, receptors, and regulatory proteins from three categories of regulatory pathway play synergistic regulatory roles during the migration process: neuronal signaling, the sensory system, and environmental adaptation. The significant differential expression of growth-related hormones, thyroid receptors, haptoglobin, and prolactin receptors was similar to the results of relevant research on salmonids and steelhead trout. CONCLUSIONS: This study revealed a regulatory network that the brain of juvenile C. nasus constructs during migration, thereby providing basic knowledge on further studies could build on. This study also revealed key regulatory genes similar to salmonids and steelhead trout, thus, this study will lay a theoretical foundation for further study on migration regulation mechanism of anadromous fish species.

Cloning, expression analysis, and antibacterial propertiesof three serum amyloid A in common carp (Cyprinus carpio).

Three serum amyloid A (SAA) genes were identified from the common carp (Cyprinus carpio) by PCR and RT-PCR. Considering both direction and sequence similarity with mammal's orthologs, they were named CcSAA3a, CcSAA3b and CcSAA1. CcSAA3b and CcSAA1 are adjacent on contig LHQP01017858, suggesting that the prototype of or the simplest SAA multigene family have occurred in common carp. A phylogenetic analysis of the SAAs indicated that the fish SAAs were closer to those of invertebrates and Ornithorhynchus anatinus, a primitive mammal, than to mammalian SAAs. Quantitative real-time RT-PCR results displayed different expression profiles of three CcSAAs. The CcSAA3a was detected in all tested tissues, and was most abundant in the muscle; CcSAA3b was predominately expressed in the intestine and liver, and CcSAA1 in the skin. The expression level of CcSAA3a was higher than that of CcSAA3b and CcSAA1 in most tissues. Stimulation with Aeromonas hydrophila dramatically induced the expression of the three CcSAAs in all examined tissues, especially in the liver. Like Epinephelus coioides SAA, all of three rCcSAA fusion proteins could bind to both Gram-negative bacteria (A. hydrophila and E. coli) and Gram-positive bacterium (S. aureus), playing a role in the identification of bacteria. However, only rCcSAA3a showed significantly anti-A. hydrophila and anti-E. coli in vitro antibacterial activity assays. These results suggested that the three CcSAAs were in functional differentiation and play significant roles in the innate immunity of common carp.

Cloning and characterization of two duplicated interleukin-17A/F2 genes in common carp (Cyprinus carpio L.): Transcripts expression and bioactivity of recombinant IL-17A/F2.

Interleukin-17 (IL-17) plays an important role in inflammation and host defense in mammals. In this study, we identified two duplicated IL-17A/F2 genes in the common carp (Cyprinus carpio) (ccIL-17A/F2a and ccIL-17A/F2b), putative encoded proteins contain 140 amino acids (aa) with conserved IL-17 family motifs. Expression analysis revealed high constitutive expression of ccIL-17A/F2s in mucosal tissues, including gill, skin and intestine, their expression could be induced by Aeromonas hydrophila, suggesting a potential role in mucosal immunity. Recombinant ccIL-17A/F2a protein (rccIL-17A/F2a) produced in Escherichia coli could induce the expression of proinflammatory cytokines (IL-1ß) and the antimicrobial peptides S100A1, S100A10a and S100A10b in the primary kidney in a dose- and time-dependent manner. Above findings suggest that ccIL-17A/F2 plays an important role in both proinflammatory and innate immunity. Two duplicated ccIL-17A/F2s showed different expression level with ccIL-17A/F2a higher than b, comparison of two 5' regulatory regions indicated the length from anticipated promoter to transcriptional start site (TSS) and putative transcription factor binding site (TFBS) were different. Promoter activity of ccIL-17A/F2a was 2.5 times of ccIL-17A/F2b which consistent with expression results of two genes. These suggest mutations in 5'regulatory region contributed to the differentiation of duplicated genes. To our knowledge, this is the first report to analyze 5'regulatory region of piscine IL-17 family genes.

Transcriptome analysis reveals that insulin is an immunomodulatory hormone in common carp.

Common carp (Cyprinus carpio) is a widespread freshwater fish and economically important species in China and other East Asian countries. Recent studies suggest that insulin can alter the expression of immune genes and, thus, can be regarded as an immunomodulatory hormone. To understand the mechanism of the immune response to insulin, we performed a comparative RNA-seq transcriptome analysis using livers from common carp injected with insulin (5 µg/g bodyweight) or saline as a control. After filtering the low-quality reads and removing the adaptors, the clean raw reads were assembled into 60,421 unigenes with mean length of 746.81 bp. Furthermore, 37,107 unigenes were annotated based on homology after blast search in public databases. Differentially expressed genes were identified using the fragments per kb per million fragments method and EdgeR software. In total, 782 differentially expressed genes were found. Thereinto, 444 and 338 genes were upregulated and downregulated, respectively, in the insulin-injected group. A Gene Ontology analysis indicated that these genes were concentrated in glucose metabolism, hormone secretion, andimmune system processes. Moreover, 153 enriched KEGG pathways were associated with the differentially expressed genes, including the Toll-like receptor (TLR) and nuclear factor kappa beta (NF-κB) signaling pathways. Signal transducer and activator of transcription 1 (10.56-fold), TLR3 (0.089-fold), activator protein-1 (0.007-fold), tumor necrosis factor-α (0.139-fold), and macrophage inflammatory protein-1ß (0.038-fold) expression were significantly changed after the insulin injection. This study characterized the profile of genes expression response to insulin in common carp liver for the first time and provided new insight into understanding the molecular mechanism of insulin as an immunomodulatory hormone.

Characterization and expression analysis of two distinct neuropeptide Ya paralogues in Jian carp (Cyprinus carpio var. Jian).

Two distinct neuropeptide Ya paralogues (jlNPYa1 and jlNPYa2) were cloned and characterized in Jian carp (Cyprinus carpio var. Jian), with a highly conserved organization encoded by four exons and three introns. The cDNAs for jlNPYa1 and jlNPYa2 were 693 and 730 bp in size, respectively. jlNPYa1 and jlNPYa2 both encoded a 96-amino acid protein, which shared 97.9 % identity. Phylogenetic tree showed that it has two NPYa genes, called jlNPYa1 and jlNPYa2, that presumably resulted from the tetraploidization event in the carp lineage. Analysis of expression profiles of jlNPYa1 and jlNPYa2 showed that the two NPY genes had a broad tissue distribution but expressed primarily in the forebrain, hypothalamus, testis and liver. The expression pattern was different in juvenile and adult (female and male) Jian carp. In juvenile, the highest expression level of jlNPYa1 and jlNPYa2 was detected in the testis. In adult, it was detected in the forebrain. In female hypothalamus, the expression level of jlNPYa1 was significantly higher than that of jlNPYa2. However, the opposite was true in male hypothalamus. The differing distribution patterns of the two NPY genes suggested that jlNPYa1 and jlNPYa2 might play different roles in Jian carp.

H2O2-Induced Oxidative Stress Responses in Eriocheir sinensis: Antioxidant Defense and Immune Gene Expression Dynamics.

Eriocheir sinensis, a key species in China's freshwater aquaculture, is threatened by various diseases, which were verified to be closely associated with oxidative stress. This study aimed to investigate the response of E. sinensis to hydrogen peroxide (H2O2)-induced oxidative stress to understand the biological processes behind these diseases. Crabs were exposed to different concentrations of H2O2 and their antioxidant enzyme activities and gene expressions for defense and immunity were measured. Results showed that activities of antioxidant enzymes-specificallysuperoxide dismutase (SOD), catalase (CAT), total antioxidant capacity(T-AOC), glutathione (GSH), and glutathione peroxidase (GSH-Px)-varied with exposure concentration and duration, initially increasing then decreasing. Notably, SOD, GSH-Px, and T-AOC activities dropped below control levels at 96 h. Concurrently, oxidative damage markers, including malondialdehyde (MDA), H2O2, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, increased with exposure duration. The mRNA expression of SOD, CAT, and GSH-Px also showed an initial increase followed by a decrease, peaking at 72 h. The upregulation of phenoloxidaseloxidase (proPO) and peroxinectin (PX) was also detected, but proPO was suppressed under high levels of H2O2. Heat shock protein 70 (HSP70) expression gradually increased with higher H2O2 concentrations, whereas induced nitrogen monoxide synthase (iNOS) was upregulated but decreased at 96 h. These findings emphasize H2O2's significant impact on the crab's oxidative and immune responses, highlighting the importance of understanding cellular stress responses for disease prevention and therapy development.

Transcriptomic analysis of hydrogen peroxide-induced liver dysfunction in Cyprinus carpio: Insights into protein synthesis and metabolism.

Hydrogen peroxide (H2O2), a prevalent reactive oxygen species (ROS) found in natural aquatic environments, has garnered significant attention for its potential toxicity in fish. However, the molecular mechanisms underlying this toxicity are not yet comprehensively understood. This study aimed to assess H2O2-induced liver dysfunction in common carp (Cyprinus carpio) and elucidate the underlying molecular mechanisms via biochemical and transcriptomic analyses. Common carp were divided into normal control (NC) and H2O2-treated groups (1 mM H2O2), the latter of which was exposed to H2O2 for 1 h per day over a period of 14 days. Serum biochemical analyses indicated that exposure to H2O2 resulted in moderate liver damage, characterized by elevated alanine aminotransferase (ALT) activity and lowered albumin (Alb) level. Concurrently, H2O2 exposure induced oxidative stress and modified the hepatic metabolic enzyme levels. Transcriptome analysis highlighted that 1358 and 1188 genes were significantly downregulated and upregulated, respectively, in the H2O2-treated group. These differentially expressed genes (DEGs) were significantly enriched in protein synthesis and a variety of metabolic functions such as peptide biosynthetic processes, protein transport, ribonucleoprotein complex biogenesis, oxoacid metabolic processes, and tricarboxylic acid metabolic processes. Dysregulation of protein synthesis is principally associated with the downregulation of three specific pathways: ribosome biogenesis, protein export, and protein processing in the endoplasmic reticulum (ER). Furthermore, metabolic abnormalities were primarily characterized by inhibition of the citrate cycle (TCA) and fatty acid biosynthesis. Significantly, anomalies in both protein synthesis and metabolic function may be linked to aberrant regulation of the insulin signaling pathway. These findings offer innovative insights into the mechanisms underlying H2O2 toxicity in aquatic animals, contributing to the assessment of ecological risks.

Genetic diversity of the common carp black strain population based on mtDNA (D-loop and cytb).

The common strain black carp (Cyprinus carpio var. baisenensis) is a culturally important carp strain that is raised and cultured in Guangxi Province, China. Its color reflects the interactions between the Burau people and their surrounding environment. The population of the common carp black strain was isolated and cultured in a rice-fish integration system. To explore the genetic diversity and protection of germplasm resources, we analyzed mitochondrial DNA (mtDNA) sequences, specifically the displacement loop (D-loop) and cytochrome b (Cytb), using single-nucleotide polymorphisms (SNP). We compared these sequences with those from four other local common carp populations. The study included a total of 136 adult common carps from five strain populations: the common black carp strain (HJ = 31), Jian (F = 30), Heilongjiang (H = 10), Songpu (S = 31), and Saijiang (SJ = 34). The results of the Cytb and D-loop analyses showed that the Heilongjiang carp (H) and Saijiang (SJ) populations had the highest levels of haplotype diversity (0.867 ± 0.034785) and nucleotide diversity (π = 0.0063 ± 0.000137 and 0.0093 ± 0.000411), respectively. On the other hand, the Common carp black strain population (HJ) exhibited the lowest haplotype diversity in both Cytb and D-loop, with haplotype 2 being the most commonly observed among the populations. Private haplotypes dominated the five common carp populations, which were significantly different at P<0.001. Furthermore, analyzing the coefficient of genetic differentiation (Fst), the highest genetic difference was observed between Saijiang (SJ) and Heilongjiang (H) (Fst = 0.963), whereas the lowest was observed between Songpu (S) and the Common carp black strain population (HJ) (Fst = 0.019) for the Cytb gene sequences. For the D-loop, the Common carp black strain population (HJ) and Songpu (S) (Fst = 0.7) had the highest values, and Heilongjiang (H) and Common black carp strain (HJ) had an Fst of 0.125. Additionally, the AMOVA analysis revealed a higher level of variance for the Cytb and D-loop genes, indicating lower genetic diversity within the local carp community. On the other hand, the phylogenetic tree analysis showed that the five carp populations were closely related and formed a distinct cluster. The distinct cluster of populations suggests a common ancestor or recent gene flow, possibly due to geographic proximity or migration history, and unique genetic characteristics, possibly due to adaptations or selective pressures. The results of this study provide valuable insights into the genetic diversity of the common strain black carp, which can have implications for conservation, breeding programs, evolutionary studies, and fisheries management.

[Sequences analysis of jlFABP2 and the correlation between polymorphisms and body weight gain in Cyprinus carpio var. jian].

Two replicate intestine fatty acid binding protein genes (jlFABP2a and jlFABP2b) were cloned from Cyprinus carpio var. jian using PCR. Both ORFs were 399 bp in length sharing 92.2% similarity with each other, and 88.0% and 90.5% with their counterpart in zebrafish, respectively. The gene structure of jlFABP2s was same as other FABPs, which contained four exons and three introns. Sequences and lengths of introns between 2a and 2b. were obviously different Phylogenetic tree displayed that two jlFABP2s corresponded to one zebrafish FABP2 which matches the fact that the chromosome number of common carp was twice of zebrafish. Real time-PCR showed that jlFABP2 genes mainly expressed in intestine and the expression level was very significantly higher than other tissues such as brain, liver, muscle, kidney, and gonad (P<0.01). The expression level of jlFABP2a was significantly (male, P<0.05) or very significantly (females, P<0.01) higher than 2b in intestine; and 2b was expressed slightly higher than 2a in other tissues. It seemed that 2a expressed specifically in intestine, while 2b expressed ubiquitously. Twelve and four SNP loci were found at jlFABP2a and 2b introns through comparison sequences from 8 individuals, respectively. Genotypes of I1-A15G, I1-A99G, I2-C487T, and I3-A27T on jlFABP2a were detected using PCR-RFLP in selection population of C. carpio var. jian. The SNP genotypes and individual weight gain correlation indicated that four SNPs were significantly (P<0.05 or P<0.01) associated with adult weight gain. Diplotype analysis displayed that individuals with genotype AGGGCCXX or AGGGXXAT grew faster than other individuals by 15%. The individuals with these two genotypes only occupied 9% in total selection populations, indicating the presence of large selection space. The 4 SNPs detected in this experiment can be used in C. carpio var. Jian growth selection breeding plan.

Alteration of antioxidant status, glucose metabolism, and hypoxia signal pathway in Eirocheir sinensis after acute hypoxic stress and reoxygenation.

Dissolved oxygen (DO) is crucial for the survival of Chinese mitten crab (Eirocheir sinensis); low DO levels adversely affect the health of these crabs. In this study, we evaluated the underlying response mechanism of E. sinensis to acute hypoxic stress by analyzing antioxidant parameters, glycolytic indicators, and hypoxia signaling factors. The crabs were exposed to hypoxia for 0, 3, 6, 12, and 24 h and reoxygenated for 1, 3, 6, 12, and 24 h. The hepatopancreas, muscle, gill, and hemolymph were sampled at different exposure times to detect the biochemical parameters and gene expression. The results showed that the activity of catalase, antioxidants, and malondialdehyde in tissues significantly increased under acute hypoxia and gradually decreased during the reoxygenation phase. Under acute hypoxic stress, glycolysis indices, including hexokinase (HK), phosphofructokinase, pyruvate kinase (PK), pyruvic acid (PA), lactate dehydrogenase (LDH), lactic acid (LA), succinate dehydrogenase (SDH), glucose, and glycogen in the hepatopancreas, hemolymph, and gills increased to varying degrees but recovered to the control levels after reoxygenation. Gene expression data showed that hypoxia signaling pathway-related genes, including hypoxia-inducible factor-1α/ß (HIF1α/ß), prolyl hydroxylase (PHD), factor inhibiting hypoxia-inducible factor (FIH), and glycolysis-related factors (HK and PK) were upregulated, showing that the HIF signaling pathway was activated under hypoxic conditions. In conclusion, acute hypoxic exposure activated the antioxidant defense system, glycolysis, and HIF pathway to respond to adverse conditions. These data contribute to elucidating the defense and adaptive mechanisms of crustaceans to acute hypoxic stress and reoxygenation.

Comparative Analysis of Transposable Elements Reveals the Diversity of Transposable Elements in Decapoda and Their Effects on Genomic Evolution.

Transposable elements (TEs) are mobile genetic elements that exist in the host genome and exert considerable influence on the evolution of the host genome. Since crustaceans, including decapoda, are considered ideal models for studying the relationship between adaptive evolution and TEs, TEs were identified and classified in the genomes of eight decapoda species and one diplostraca species (as the outgroup) using two strategies, namely homology-based annotation and de novo annotation. The statistics and classification of TEs showed that their proportion in the genome and their taxonomic composition in decapoda were different. Moreover, correlation analysis and transcriptome data demonstrated that there were more PIF-Harbinger TEs in the genomes of Eriocheir sinensis and Scylla paramamosain, and the expression patterns of PIF-Harbingers were significantly altered under air exposure stress conditions. These results signaled that PIF-Harbingers expanded in the genome of E. sinensis and S. paramamosain and might be related to their air exposure tolerance levels. Meanwhile, sequence alignment revealed that some Jockey-like sequences (JLSs) with high similarity to specific regions of the White spot syndrome virus (WSSV) genome existed in all eight decapod species. At the same time, phylogenetic comparison exposed that the phylogenetic tree constructed by JLSs was not in agreement with that of the species tree, and the distribution of each branch was significantly different. The abovementioned results signaled that these WSSV-specific JLSs might transfer horizontally and contribute to the emergence of WSSV. This study accumulated data for expanding research on TEs in decapod species and also provided new insights and future direction for the breeding of stress-resistant and disease-resistant crab breeds.

Effects of different temperatures on growth and intestinal microbial composition of juvenile Eriocheir sinensis.

The change in temperature will change the composition of intestinal microorganisms of juvenile Eriocheir sinensis, and the composition of intestinal microorganisms will affect the growth and development of juvenile crabs. In order to explore the relationship between intestinal microorganisms and growth of E. sinensis at different temperatures, the status of growth and intestinal microflora of juvenile E. sinensis reared at different water temperatures (15 °C, 23 °C, and 30 °C) were compared in this study. The results showed that the respective survival rate of juvenile E. sinensis in the three water temperature groups was 100%, 87.5%, and 64.44%. Moreover, the molting rate increased with an increase in water temperature, which was at 0%, 10%, and 71.11% for the three respective temperature groups. The average weight gain rate showed an overall increasing trend with the increase of water temperature. Moreover, the final fatness of the crabs in the 30 °C water temperature group was significantly lower than that in the 15 °C and 23 °C groups (p < 0.05); there was no significant difference in the liver-to-body ratio among the three groups. The results of the alpha diversity analysis of the 16S rRNA data revealed that there was no significant difference in the intestinal microbial abundance among the three water temperature groups; however, the intestinal microbial diversity in the 23 °C water temperature group was significantly lower than that in the 15 °C and 30 °C groups. At the phylum level, the dominant flora of the three groups was Firmicutes, Proteobacteria, and Bacteroidota. At the genus level, the abundance of Parabacteroides and Aeromonas in the intestine of the crabs in the 30 °C water temperature group was significantly higher than that in the 15 °C and 23 °C groups (p < 0.05). The function prediction showed that the main functional diversity of intestinal microflora of juvenile E. sinensis in the three water temperature groups was similar and mainly involved in metabolic-related functions, but there were still differences in the effects of water temperature on functional pathways such as metabolism, immunity, and growth among each group, either promoting or inhibiting. In conclusion, different water temperatures can affect the composition and function of intestinal flora of E. sinensis, and 23 °C-30 °C is the optimal water temperature for the growth of juvenile E. sinensis.