To analyze growth trait differences and genetic characteristics of Siniperca chuatsi from distinct geographic populations, whole-genome resequencing was performed on 90 samples from Heilongjiang (HLJ), Hubei (HB), Hunan (HN), and Anhui (AH), and for the first time, population-unique growth-related loci were detected. Population structure analysis indicated that the four populations were genetically distinct (K = 4). A preliminary Genome-Wide Association Study (GWAS) revealed 26 significant growth-related SNPs linked to 158 potential functional genes, which were primarily enriched in Metabolic pathways, the NOD-like receptor signaling pathway, and Necroptosis, suggesting their possible roles in growth regulation. Non-tag SNP capture within functional genes yielded 24 known significant loci and 118 potentially linked loci. On this basis, one-way ANOVA ultimately identified 13 SNPs significantly associated with growth, and their advantageous genotypes were characterized. Notably, this study revealed, for the first time, that the HLJ population possesses six population-unique genotypes significantly linked to superior growth traits, which may represent population-restricted candidate markers associated with growth-related variation. The results of this study provide new candidate molecular markers and supporting data that may inform future breeding strategies pending further validation.

Onychostoma lini is an ecologically and economically important cyprinid species endemic to the mountain rivers of southern China. Wild populations have sharply declined due to habitat fragmentation, hydropower development, and overexploitation, yet genomic information remains unavailable, hindering studies on its diversity, adaptation, and conservation. Here, we assembled the first chromosome-level genome of O. lini using PacBio HiFi long-read sequencing, Illumina short-read polishing, and Hi-C scaffolding. The 907.5 Mb assembly achieved a contig N50 of 32.83 Mb and a scaffold N50 of 34.89 Mb, with 99.93% of sequences anchored to 25 chromosomes. Repetitive elements occupied 387.36 Mb, representing 42.69% of the genome. We predicted 28,597 protein-coding genes, 99.05% of which were functionally annotated in NR, KEGG, InterPro, SwissProt, and GO databases. BUSCO analysis identified 97.9% complete orthologs, confirming assembly completeness and annotation accuracy. This high-quality reference genome provides a foundational resource for investigating cyprinid evolution, environmental adaptation, and molecular breeding, and supports the conservation of O. lini.

This study aimed to investigate the response mechanisms of liver and gill tissues in mandarin fish (Siniperca chuatsi) at the histological, apoptotic, and gene expression levels during the weaning process from live prey to artificial feed. By analyzing fish samples at different domestication stages (D0, D7, D14), the results revealed that: (1) Histologically, the gill filaments exhibited shortening and thickening post-domestication, while the liver showed increased vacuolation; (2) apoptosis detection (TUNEL assay) and analysis of apoptosis-related gene (Bax/Bcl-2) expression indicated that the gill tissue experienced a significant increase in apoptosis at the mid-domestication stage (D7), which returned to baseline levels later (D14), whereas hepatic apoptosis showed no significant changes throughout the process; (3) transcriptome sequencing identified 3405 and 881 differentially expressed genes (DEGs) in the liver and gill tissues, respectively, and the significantly enriched pathways were steroid biosynthesis in the liver and alanine, aspartate, and glutamate metabolism in the gills. The apoptosis pathway was also significantly enriched in both tissues. GO analysis further indicated that the DEGs were primarily associated with metabolic processes, oxidative stress, and cell apoptosis. In conclusion, artificial feed domestication induces adaptive changes in the tissue structure and molecular profiles of the gill and liver in mandarin fish. The gill response to dietary transition is more rapid and characterized by a reversible apoptotic process, providing a theoretical foundation for understanding the stress mechanisms associated with domestication and promoting healthy aquaculture practices for this species.

Glufosinate (GLUF) and glyphosate (GLY) are nonselective phosphorus-containing amino acid herbicides that are widely used in agricultural gardens and noncultivated areas. These herbicides give rise to a number of key metabolites, with 3-methyl phosphinicopropionic acid (MPPA), N-acetyl glufosinate (N-acetyl GLUF), aminomethyl phosphonic acid (AMPA), N-acetyl aminomethyl phosphonic acid (N-acetyl AMPA), N-acetyl glyphosate (N-acetyl GLY), N-methyl glyphosate (N-methyl GLY) as the major metabolites obtained from GLUF and GLY. Extensive use of these herbicides may lead to their increased presence in the environment, especially aquatic ecosystems. An increasing number of research studies into the toxicities of GLUF, GLY, and their metabolites have shown that these herbicides are potentially toxic to aquatic biota. GLUF and GLY, as well as their metabolites, are extremely polar and water-soluble, and they lack chromogenic and fluorescent groups; therefore, their concentrations are difficult to determine using conventional methods. Most analytical methods used to date have largely depended on derivatization procedures, leading to overall determination processes that are tedious and time-consuming. Therefore, establishing a quick and sensitive method that does not require derivatives for determining GLUF, GLY, and their metabolites in water environments, including surface water, sediments, and aquatic organisms, is an important endeavor. In this study, a new approach was developed based on pass-through solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine GLUF, GLY, and their metabolites, including MPPA, N-acetyl GLUF, AMPA, N-acetyl AMPA, N-acetyl GLY, and N-methyl GLY, in sediments. Samples were extracted with 4% (v/v) ammonia water and purified using PRiME HLB pass-through solid-phase extraction columns. The extracts were filtered through a polyethersulfone microfiltration membrane and analyzed by UHPLC-MS/MS. Compounds were separated on a Metrosep A Supp 5 column (150 mm×4.0 mm, 5 μm) using gradient elution with water and 200 mmol/L ammonium hydrogen carbonate solution containing 0.05% (v/v) ammonia water as the mobile phases. Analytes were detected using MS/MS with a negative electrospray ionization (ESI-) source in the multiple reaction monitoring (MRM) mode. A matrix-matched external-standard approach was used for quantitative analysis. GLUF, GLY, and their metabolites were detected within 15 min with good peak shapes and high responses. Calibration curves were linear in the range of 2.0-200 μg/L, with correlation coefficients exceeding 0.995. This method delivered limits of detection (LODs) and limits of quantification (LOQs) of 5 μg/kg and 20 μg/kg, respectively, for GLUF, MPPA, N-acetyl-GLUF, N-acetyl AMPA, N-acetyl GLY, and N-methyl GLY, and 10 μg/kg and 30 μg/kg, for GLY and AMPA, respectively. Average spiked recoveries at three levels (LOQ, 5LOQ, 10LOQ) in sediment with low organic matter content were in the range of 78.5%-107%, and the relative standard deviations (RSDs) were in the range of 1.32%-14.7% (n=6). Average spiked recoveries of 76.4%-113% were determined for three levels (LOQ, 5LOQ, and 10LOQ) in sediments with high organic matter contents, with RSDs of 2.60%-11.2% (n=6). The developed method was used to analyze GLUF, GLY, and their metabolites in ponds, lakes, reservoirs, and river sediments. No target compounds were detected in any sediment sample obtained from a lake, reservoir, or river; however, GLY and AMPA were detected in one pond-sediment sample at levels of 31.7 and 52.3 μg/kg, respectively. The developed approach is simple, fast, and green; moreover, it offers advantages, including high accuracies, high sensitivities, and good reproducibilities. Accordingly, the developed method is suitable for determining GLUF, GLY, and their metabolites in sediments and can provide technical support for studying residue characteristics and environmental behavior in sediments.

Decorus tungting is a vulnerable, endemic cyprinid species of conservation significance, historically abundant in Dongting Lake but now suffering severe population declines due to overfishing and river modifications. However, no genome assembly has been reported for D. tungting, limiting insights into its genetic diversity, adaptive potential, and effective conservation management. Here, we assembled the first chromosome-level genome of D.tungting using PacBio HiFi long-read sequencing, Illumina short-read polishing, and Hi-C chromatin interaction mapping. The 1.14 Gb assembly has a contig N50 of 6.04 Mb and a scaffold N50 of 44.81 Mb, with 99.31% of sequences anchored to 25 chromosomes. Repetitive elements span 574.36 Mb, accounting for 50.28% of the genome. We annotated 24,835 protein-coding genes and 7,312 non-coding RNAs, with BUSCO completeness score of 97.1% in genome mode and 92.7% in protein mode, supporting assembly accuracy and annotation integrity. This high-quality genome assembly of Decorus tungting provides a foundational resource for genetic diversity, adaptive evolution, and evidence-based conservation.

This study aimed to determine the optimal dietary lipid requirement and assess gut microbiota composition in juvenile Spinibarbus caldwelli. Five iso-nitrogenous diets containing graded lipid levels (L1: 2.29 %, L2: 4.54 %, L3: 6.35 %, L4: 8.07 %, L5: 10.04 %) were formulated and fed to S. caldwelli (initial body weight: 2.70 +/- 0.01 g) for 56 days. A total of 450 fish were randomly allocated into 15 tanks (3 replicates per group, 30 fish per tank). The results revealed that: 1) Although no significant differences (P > 0.05) were observed in WG, SGR, and SR, these parameters exhibited a declining trend with increasing dietary lipid levels. 2) Muscle crude protein content in the L2 group was significantly higher than that in other groups (P < 0.05), accompanied by distinct variations in lipid and moisture contents. 3) The L2 group displayed markedly elevated concentrations of SFAs and PUFAs in muscle tissue compared to other dietary treatments (P < 0.05). 4) Hepatic and intestinal enzyme activities were significantly enhanced in the L2 and L3 groups (P < 0.05), with optimal performance observed at moderate lipid levels. 5) Intestinal microbiota analysis indicated that the L2 group exhibited significantly higher Shannon, Pielou E, and Simpson indices than other groups (P < 0.05). In conclusion, the L2 group demonstrated superior hepatic antioxidant capacity, enhanced intestinal digestive and lipid metabolic enzyme activities (P < 0.05), and a more diverse and abundant gut microbial community. The analysis results suggested that a 4.54 % dietary lipid level is optimal for juvenile S. caldwelli under the experimental conditions, providing critical insights for formulating species-specific aquafeeds.

Calmodulin (Calm), a crucial Ca2+ sensor, plays an important role in calcium-dependent signal transduction cascades. However, the expression and the relevance of Calm in stress and immune response have not been characterized in Megalobrama amblycephala. In this study, we identified the full-length cDNA of Calm (termed MaCalm) in blunt snout bream M. amblycephala, and analyzed MaCalm expression patterns in response to cadmium and Aeromonas hydrophila challenges. MaCalm was 1603 bp long, including a 5′-terminal untranslated region (UTR) of 97 bp, a 3′-terminal UTR of 1056 bp and an open reading frame (ORF) of 450 bp encoding a polypeptide of 149 amino acids with a calculated molecular weight (MW) of 16.84 kDa and an isoelectric point (pI) of 4.09. Usually, MaCalm contains four conservative EF hand motifs. The phylogenetic tree analysis indicated that the nucleotide sequence of MaCalm specifically clustered with Ctenopharyngodon idella with high identity (98.33%). Tissue distribution analysis demonstrated that the ubiquitous expression of MaCalm mRNA was found in all tested tissues, with the highest expression in the brain and the lowest expression in muscle. MaCalm showed significant upregulation at 14 d and 28 d post exposure to varying concentrations of cadmium in the liver; HSP70 transcripts in the liver significantly upregulated at 14 d post exposure to different concentrations of cadmium. Moreover, in response to the A. hydrophila challenge in vivo, MaCalm transcripts in the liver first increased and then decreased, but MaCalm transcripts in the kidney declined gradually with prolonged infection. After the A. hydrophila challenge, the expression level of HSP70 was significantly downregulated at 24 h in the liver and its expression level was notably downregulated at 12 h and at 24 h in the kidney. Collectively, our results suggest that MaCalm possesses vital roles in stress and immune response in M. amblycephala.

Niclosamide (NIC) is a commonly used insecticide and molluscicide in the prevention and treatment of parasitic diseases in fish. The utilization of NIC has the potential to disrupt the microbial community present on the mucosal tissue of fish, leading to localized inflammatory responses. The objective of this study was to evaluate the impact of NIC on the immune system and bacterial populations within the gill and gut of Mylopharyngodon piceus. Fish were subjected to varying concentrations of NIC, including a control group (0 μg/L), a low NIC group (15% 96 h LC50, LNG, 9.8 μg/L), and a high NIC group (80% 96 h LC50, HNG, 52.5 μg/L). Gill and gut samples were collected 28 days post-exposure for analysis. The findings revealed that the 96-h LC50 for NIC was determined to be 65.7 μg/L, and histopathological examination demonstrated that exposure to NIC resulted in gill filament subepithelial edema, exfoliation, degeneration, and a decrease in gill filament length. Furthermore, the gut exhibited apical enterocyte degeneration and leucocyte infiltration following NIC exposure. Additionally, NIC exposure led to a significant elevation in the levels of immunoglobulin M (IgM), complement component 3 (C3), and complement component 4 (C4) in both gill and gut tissues. Moreover, the activity of lysozyme (LYZ) was enhanced in the gill, while the activities of peroxidase (POD) and immunoglobulin T (IgT) were increased in gut tissue. The exposure to NIC resulted in enhanced mRNA expression of c3, c9, tnfα, il6, il8, and il11 in the gill tissue, while decreasing c3 and il8 expression in the gut tissue. Furthermore, the natural resistance-associated macrophage protein (nramp) mRNA increased, and liver-expressed antimicrobial peptide 2 (leap2) mRNA decreased in gill and gut tissues. And hepcidin (hepc) mRNA levels rose in gill but fell in gut tissue. NIC exposure also led to a decrease in gill bacterial richness and diversity, which significantly differed from the control group, although this separation was not significant in the gut tissue. In conclusion, the administration of NIC resulted in alterations in both the immune response and mucosal microbiota of fish. Furthermore, it was noted that gills displayed a heightened vulnerability to sublethal effects of NIC in comparison to gut tissues.

ABSTRACTFreshwater ecosystems face unprecedented challenges as the cumulative impact of human activities intensifies. While protected areas and species‐specific conservation policies are widely implemented, their effectiveness remains difficult to gauge using traditional catch‐based surveys. This research employed environmental DNA (eDNA) technology to assess the distribution of the endangered fish, Bangana tungting, within the Yuanshui Unique Fish Species National Aquatic Germplasm Resources Reserve (YUFRR) in Hunan, China. Over a 2‐year period, we conducted comprehensive eDNA survey multiple sites within the YUFRR, confirming the species' continued existence in the area. In September 2022, B. tungting eDNA was detected at 8 of 60 sampling locations, while a follow‐up survey in May 2023 identified its presence at 4 of 44 sites. Further analysis revealed critical environmental factors influencing B. tungting distribution, primarily dissolved oxygen concentration and the presence of physical barriers such as hydroelectric stations. Our data suggest a minimum dissolved oxygen tolerance threshold of 4 mg/L for this species. Moreover, we observed an inverse relationship between B. tungting detection rates and both the number of hydroelectric stations and their distance to sampling sites. This case study demonstrates the effectiveness of eDNA technology in mapping the distribution of endangered fish species like B. tungting and guiding conservation strategies. Our findings emphasize the crucial need to enhance environmental conditions, particularly water quality and habitat suitability, to ensure the effective conservation of B. tungting within the YUFRR.

Niclosamide (NIC) is a potent salicylanilide molluscicide/helminthicide commonly utilized for parasite and mollusc control in aquatic environments. Due to its persistent presence in water bodies, there is growing concern regarding its impact on aquatic organisms, yet this remains inadequately elucidated. Consequently, this study aims to assess the hepatotoxic effects and detoxification capacity of black carp (Mylopharyngodon piceus) in a semi-static system, employing various parameters for analysis. NIC was applied to juvenile black carp at three different concentrations (0, 10 and 50 μg/L) for 28 days in an environmentally realistic manner. Exposure to 50 μg/L NIC resulted in an increase in hepatic lysozyme (LYZ), alkaline phosphatase (ALP), and complement 4 (C4) levels while simultaneously causing a decrease in peroxidase (POD) activity. Additionally, NIC exposure exhibited a dose-dependent effect on elevating serum levels of LYZ, ALP, complement 3 (C3), C4, and immunoglobulin T (IgT). Notably, the mRNA levels of immune-related genes tnfα, il8, and il6, as well as nramp and leap2, were upregulated in fish exposed to NIC. RNA-Seq analysis identified 219 differentially expressed genes (DEGs) in M. piceus after NIC exposure, with 94 upregulated and 125 downregulated genes. KEGG and GO analyses showed enrichment in drug metabolism pathways and activities related to oxidoreductase, lip oprotein particles, and cholesterol transport at 50 μg/L NIC. Additionally, numerous genes associated with lipid metabolism, oxidative stress, and innate immunity were upregulated in NIC-exposed M. piceus. Taken together, these findings indicate that NIC has the potential to cause hepatotoxicity and immunotoxicity in M. piceus. This research offers important insights for further understanding the impact of molluscicide/helminthicide aquatic toxicity in ecosystems.

To clarify the allometric growth pattern and hunger tolerance of Hemibarbus maculatus Bleeker larvae, the morphological lengths of their functional organs were measured continuously and their primary feeding rates under a state of starvation were studied. A control group and starvation group were set up for this study, and 10 larvae were sampled from each group every day in order to study their allometric growth pattern and starvation tolerance. The results indicated that the Hemibarbus maculatus larvae opened their mouths for feeding at 4 days after hatching, and that the yolk sac disappeared completely at 11 days after hatching. The Hemibarbus maculatus larvae preferentially developed their heads, fins, and eyes, related to the functions of feeding, balancing, and swimming, in order to cope with complex environments. The growth inflection points for the head length, pectoral fin length, dorsal fin length, eye diameter, eye spacing, snout length, and body height were characterized by total lengths of 10.93 mm, 11.67 mm, 11.67 mm, 13.17 mm, 16.53 mm, 15.13 mm, and 15.13 mm, respectively. Prior to and following the inflection point, positive allometric growth was observed in all organs. After the inflection point, the dorsal fin continued to maintain positive allometric growth, while the others changed to isometric allometric growth. A growth inflection point was not observed for trunk length or the lengths of the tail and anal fins. The trunk length always maintained negative allometry, while the tail and anal fin lengths were reversed. The growth inflection point of the tail length was at a total length of 13.68 mm. Before and after the growth inflection point, negative and isometric allometric growths were observed, respectively. According to the relationship between the total length and number of days after hatching, the growth inflection point of the Hemibarbus maculatus larvae was concentrated at TL = 10.93–16.53 mm, which was observed 14–20 days after hatching. The point of no return for the Hemibarbus maculatus larvae was 12–13 days after hatching, and the ratio of days after hatching in the mixed trophic period to the endotrophic period was 1.75, indicating that the larvae had strong hunger tolerance. Therefore, when considering a water temperature of 22.66 ± 1.56 °C, 4–5 days after hatching is the best time to cultivate in the pond, and it should not be carried out later than 12 days after hatching.

To investigate whether Mandarin fish developed oxidative stress after being domesticated with artificial feed, we conducted a series of experiments. Oxidative stress is an important factor leading to diseases and aging in the body. The liver integrates functions such as digestion, metabolism, detoxification, coagulation, and immune regulation, while the gills are important respiratory organs that are sensitive to changes in the water environment. Therefore, we used the liver and gills of Mandarin fish as research materials. The aim of this study was to investigate the effects of short-term artificial feed domestication on the expression of oxidative stress genes and the changes in oxidative-stress-related enzyme activity in the liver and gills of Mandarin fish. We divided the Mandarin fish into two groups for treatment. The control group was fed with live bait continuously for 14 days, while the experimental group was fed with half artificial feed and half live bait from 0 to 7 days (T-7 d), followed by solely artificial feed from 7 to 14 days (T-14 d). The experimental results showed that there was no difference in the body weight, length, and standard growth rate of the Mandarin fish between the two groups of treatments; after two treatments, there were differences in the expression of genes related to oxidative stress in the gills (keap1, kappa, gsta, gstt1, gstk1, SOD, and CAT) and in the liver (GPx, keap1, kappa, gsta, gstt1, gr, and SOD). In the liver, GPx activity and the content of MDA were significantly upregulated after 7 days of domestication, while in the gills, SOD activity was significantly upregulated after 7 days of domestication and GPx activity was significantly downregulated after 14 days of domestication. These results suggest that artificial feed domestication is associated with oxidative stress. Moreover, these results provide experimental basic data for increasing the production of aquaculture feed for Mandarin fish.

Efficient and safe extraction of microRNAs (miRNAs) from biological samples is pivotal for genetic regulation studies and biotechnological applications. This study focuses on optimizing the microRNA extraction process from the plasma of common carp, a significant species in aquaculture. Recognizing the limitations and hazards of commercial extraction kits, which often employ toxic chemicals like phenol and chloroform, we sought to develop a safer and more effective alternative. Our optimized protocol utilizes guanidinium isothiocyanate (GITC) and sarkosyl, omitting hazardous substances. We explored several parameters including GITC concentration, the addition of sarkosyl, and the role of sodium chloride in enhancing miRNA yield. Our findings demonstrate that optimal conditions involve a GITC concentration of 4.2 M, a 3% sarkosyl concentration, and the use of sodium chloride at 0.5 M. We also investigated the utility of glycogen as a nucleic acid carrier, finding 160 mu g to be the optimal concentration. Comparative analysis with commercial kits indicated our method provides higher miRNA yields with reduced cycle threshold values, underscoring the effectiveness of our custom protocol. This optimized approach not only enhances miRNA recovery but also emphasizes safety and cost-effectiveness, making it a valuable method for both research and practical applications in aquaculture.

TBK1 is an important IFN antiviral signalling factor, and in previous work black carp TBK1 (bcTBK1) and black carp IRF5 (bcIRF5) together promoted cell death in GCRV-infected cells. In this research, bcTBK1 and bcIRF5 were investigated both in vivo and in vitro to delineate their individual and combined functions. This study demonstrated that both bcTBK1 and bcIRF5 expressions were modulated in response to GCRV infection across the intestine, gill, kidney and spleen. In bcgill cells, overexpression of bcTBK1 and bcIRF5 initially suppressed the expression of cell death-related genes, including RIPK1, caspase1, caspase3 and bax, but this suppression was negated upon GCRV infection. In vivo, mRNA expression levels of RIPK1 and related genes varied by tissue following bcTBK1 or bcIRF5 overexpression and GCRV infection. Notably, intracellular co-overexpression of bcTBK1 and bcIRF5 led to significant upregulation of caspase3, caspase1, bax, and IL1β, along with enhanced caspase3 activity post-GCRV infection. This co-expression correlated with higher survival rates in black carp during GCRV infection and increased caspase3 mRNA in the spleen and gills. Hematoxylin-eosin (HE) staining indicated disorganized spleen tissue and edematous, hyperplastic gill changes in co-transfected groups after infection. TUNEL staining of tissue sections showed that DNA breakage was significantly stronger in the co-transfected group than in the other groups during GCRV infection. Further phosphorylation experiments showed that bcIRF5 promoted phosphorylation modification of bcTBK1. Thus, these data suggest that bcIRF5 activates bcTBK1 by enhancing its phosphorylation and promotes PANoptosis in GCRV-infected cells.

In this study, juvenile crayfish hatched from the same population were cultured in different growing environments: pond (D1), paddy field (D2), and aquaculture barrel (D3), and fed for 60 days. Crayfishes were selected randomly, females and males, 50 tails each from six groups (D1-♀, D1-♂, D2-♀, D2-♂, D3-♀, D3-♂) to measure the following morphological traits: full length (X1), body length (X2), chelicerae length (X3), chelicerae weight (X4), cephalothorax length (X5), cephalothorax width (X6), cephalothorax height (X7), eye spacing (X8), caudal peduncle length (X9), and caudal peduncle weight (X10). We found that the coefficient of variation (CV) of X4 was the largest in each culture mode, and males (28.58%~38.67%) were larger than females (37.76%~66.74%). The CV of X4 of crayfish cultured in D1 and D2 was larger than that of D3. All traits except X8 were positively correlated with body weight (p < 0.05). After pathway analysis, we found that X4, X5, X7, and X10 were significantly correlated with the body weight of D1-♀; the equation was YD1-♀ = −29.803 + 1.249X4 + 0.505X5 + 0.701X7 + 1.483X10 (R2 = 0.947). However, X2, X4, and X6 were significantly correlated with the body weight of D1-♂; the equation was YD1-♂ = −40.881 + 0.39X2 + 0.845X4 + 1.142X6 (R2 = 0.927). In D2-♀, X1, X4, X5, and X10 were significantly correlated with body weight; the equation was YD2-♀ = −12.248 + 0.088X1 + 1.098X4 + 0.275X5 + 0.904X10 (R2 = 0.977). X4 and X5 played a major role in the body weight of D2-♂ with the equation: YD2-♂ = −24.871 + 1.177X4 + 0.902X5 (R2 = 0.973). X3 and X10 mainly contributed to the body weight of D3-♀ with the equation: YD3-♀ = −22.476 + 0.432X3 + 3.153X10 (R2 = 0.976). X1 and X4 mainly contributed to the body weight of D3-♂ with the equation: YD3-♂ = −34.434 + 0.363X1 + 0.669X4 (R2 = 0.918). Comparing the pathway analysis with the gray relation analysis, we could conclude that the traits most correlated with body weight in D1-♀ were X10 and X7; in D1-♂, X6; in D2-♀, X10, X1, and X5; in D2-♂, X5; in D3-♀, X10; and in D3-♂, X4 and X1.

Parasitic infestations present significant threats to the physiological health and ecological stability of aquatic species, frequently compromising immune defenses and elevating mortality rates. This study was conducted to elucidate the non-specific immune responses induced by Pallisentis (Neosentis) celatus infection in Monopterus albus, with a focus on intestinal histopathology and transcriptome gene expression. A histopathological examination revealed minor alterations in intestinal villi under low-level infection. A transcriptome analysis, performed using Illumina sequencing technology, identified 347 upregulated and 298 downregulated genes involved in critical biological pathways, such as lipid metabolism, immune responses, and the regulation of inflammatory processes. GO and KEGG analyses indicated the upregulation of immune-related pathways, including the RIG-I-like and IL-17 signaling pathways, highlighting a robust intestinal immune response. Conversely, the complement pathway was found to be downregulated, with significant suppression of C9, suggesting that the parasite may engage in immune evasion. Fluorescein-labeled C9 antibody assays confirmed reduced complement C9 levels in the infected tissues. A real-time PCR analysis identified the differential expression of eight genes, including C5, maats1, CFI, and gmnc, which were consistent with the sequencing results. These findings suggest that Pallisentis (Neosentis) celatus infection compromises intestinal health, induces inflammation, and activates non-specific immune responses in Monopterus albus. However, Pallisentis (Neosentis) celatus appears to evade the host immune response by suppressing the activation of complement components, thereby facilitating its reproductive parasitism.

Deltamethrin (Del), a widely administered pyrethroid insecticide, has been established as a common contaminant of the freshwater environment and detected in many freshwater ecosystems. In this study, we investigated the changes in brain transcriptome and metabolome of crucian carp after exposure to 0.6 μg/L Del for 28 days. Elevated MDA levels and inhibition of SOD activity indicate damage to the antioxidant system. Moreover, a total of 70 differential metabolites (DMs) were identified using the liquid chromatography-mass spectrometry, including 32 upregulated and 38 downregulated DMs in the Del-exposed group. The DMs associated with chronic Del exposure were enriched in steroid hormone biosynthesis, fatty acid metabolism, and glycerophospholipid metabolism for prostaglandin G2, 5-oxoeicosatetraenoic acid, progesterone, androsterone, etiocholanolone, and hydrocortisone. Transcriptomics analysis revealed that chronic Del exposure caused lipid metabolism disorder, endocrine disruption, and proinflammatory immune response by upregulating the pla2g4, cox2, log5, ptgis, lcn, and cbr expression. Importantly, the integrative analysis of transcriptomics and metabolomics indicated that the arachidonic acid metabolism pathway and steroid hormone biosynthesis were decisive processes in the brain tissue of crucian carp after Del exposure. Furthermore, Del exposure perturbed the tight junction, HIF-1 signaling pathway, and thyroid hormone signaling pathway. Overall, transcriptome and metabolome data of our study offer a new insight to assess the risk of chronic Del exposure in fish brains.