Search Results (1,464)

Largemouth bass (Micropterus salmoides) is a major freshwater farmed species in China, making substantial economic contributions owing to its desirable flesh quality, rapid growth, and strong acceptance of formulated feeds. This study assessed the effects of dietary supplementation (intermittent and continuous feeding group, n = 3) with the probiotic Bacillus velezensis (1.0 × 10⁹ CFU/g) on growth performance, intestinal morphology, digestive enzyme activities, and gut microbial diversity in this fish. The results indicated that continuous B. velezensis administration significantly increased percentage weight gain, specific growth rate, and survival, while concurrently reducing feed conversion ratio relative to the basal diet (p < 0.05). Intermittent feeding also resulted in a markedly higher survival rate and a lower FCR. Histological examination of intestinal sections revealed elevated villus height, villus width, and muscularis thickness in the B. velezensis supplemented groups, with the intermittent regimen producing more pronounced effects. Compared with the control, the intermittent group exhibited substantially decreased the pepsin and lipase activities of the serum. In the continuous group, serum globulin levels rose noticeably, accompanied by significant declines in total complement and superoxide dismutase. Moreover, continuous B. velezensis supplementation markedly upregulated the expression levels of TGFβ, myd88, IL34, IL8, and TNFα in the head-kidney of the largemouth bass, whereas intermittent supplementation significantly increased TGFβ, Gpx, Nrf2, and Acp transcript levels. Dietary inclusion of B. velezensis was also found to enhance intestinal microbial richness and greatly increase the abundance of potentially beneficial bacteria. Collectively, these results indicate that B. velezensis supplementation exerts beneficial effects on intestinal digestive capacity, growth, and innate immunity, thereby lowering disease susceptibility in largemouth bass. Full article

The northern margin of the East Asian tropics harbors exceptional endemism, yet its freshwater fish fauna remains poorly characterized. Tachysurus virgatus, long considered a single widespread species in this region, exemplifies this taxonomic gap. Through integrative taxonomic analyses combining morphological and molecular evidence, we uncovered remarkable cryptic diversity within this species. Phylogenetic reconstructions reveal that true T. virgatus is restricted to the Wanquan River basin on Hainan Island, whereas nine additional lineages from other drainages represent previously unrecognized species described in this study. Together with two known congeners (T. spilotus and T. kyphus), these form the monophyletic T. virgatus species group for which we provide morphological diagnoses. Pronounced incongruence between morphological and molecular divergence characterizes this group, underscoring the necessity of integrative approaches for species delimitation in morphologically conserved lineages. Moreover, distinct habitat specialization patterns were identified within the group, with species exhibiting adaptations to three ecological niches: mainstem river, montane streams, and generalist habitats occupying both. Correlations between habitat preferences and functional morphology were preliminarily discussed. Using our revised taxonomic framework, we evaluated the conservation status of all species under IUCN Red List criteria, with several newly described taxa warranting threatened status due to extremely limited distributions. This study highlights the pervasive cryptic diversity of freshwater fishes in the north margin of East Asian tropics and emphasizes the critical importance of rigorous taxonomic resolution to guide effective conservation in this biogeographically complex region. Full article

Advances in biotechnological tools have accelerated the genomic characterization of non-model organisms, providing insights for broader bioprospecting efforts. In this context, Hyphessobrycon, one of the most species-rich and widely distributed genera in the family Characidae, remains largely unexplored at the mitogenomic level. We sequenced the complete mitogenomes of three Hyphessobrycon species, compared them with those of other Hyphessobrycon species, and conducted a phylogenetic analysis. We found that Hyphessobrycon mitogenomes are similar in terms of structure and size, codons with relative synonymous codon usage >1 usually end with A or T, and the genus Hyphessobrycon is polyphyletic. Our study provides additional evidence for the phylogenetic relationships in Characidae; however, mitogenomes of more Hyphessobrycon species need to be characterized in future studies. Full article

Anthropogenic particles (APs), including suspected microplastics, are increasingly reported in freshwater ecosystems; however, baseline data remain limited for culturally important freshwater fish in the Mississippi River Headwaters. This study assessed the occurrence and morphology of APs in Ogaa (walleye; Sander vitreus) and Asaawe (yellow perch; Perca flavescens) collected from five northern Minnesota lakes. Gastrointestinal tract, liver, and fillet tissues from 49 fish were processed using a modified hydrogen peroxide digestion protocol and examined by stereomicroscopy. Because polymer confirmation was not conducted, visually identified particles are conservatively reported as anthropogenic particles rather than confirmed microplastics. Forty-one APs were identified across all tissues, with 43% of fish containing at least one particle ($0.83\pm 1.$ particles per fish). Fibers were the predominant morphology, followed by fragments, and walleye exhibited greater AP prevalence and abundance than yellow perch. Although descriptive differences were observed among lakes and tissues, statistical analyses did not detect significant relationships among the variables examined. These findings establish baseline information on AP occurrence in culturally important freshwater fish from the Mississippi River Headwaters and provide a foundation for future investigations incorporating polymer confirmation and expanded spatial and temporal sampling. Full article

Overwintering represents a critical bottleneck for farmed fish, during which low temperature and starvation stress frequently co-occur, yet their synergistic effects on fish health remain poorly understood. Here, we exposed Pelteobagrus vachelli, a cold-sensitive freshwater species, to four conditions for 10 days: control (25 °C, feeding), starvation alone (25 °C, starvation), cold alone (11 °C, feeding), and combined cold–starvation (11 °C, starvation). Hepatic histopathology, antioxidant and liver function indices, gut microbiota (16S rRNA sequencing), and untargeted metabolomics (LC–MS) were integrated to elucidate gut–liver axis mechanisms underlying synergistic injury. Combined stress synergistically aggravated liver injury, as evidenced by hepatocellular vacuolation and necrosis, elevated aspartate aminotransferase (AST), alanine transaminase (ALT), malondialdehyde (MDA), and suppressed total superoxide dismutase (T–SOD), glutathione (GSH), catalase (CAT), and total antioxidant capacity (T–AOC). Two-way ANOVA confirmed significant interactive effects between cold and starvation stress (p < 0.05). Multi-omics revealed that dual stress uniquely activated multiple cell death pathways (FoxO, autophagy, ferroptosis, apoptosis), with marked oxidative phosphorylation (OXPHOS) activation and glutathione depletion—a signature absent under single stressors. Gut microbiota restructuring showed beneficial commensals (Cetobacterium, Prevotella, Lactobacillus) depleted and opportunistic pathogens (Plesiomonas, Pseudomonas, Flavobacterium) enriched, with Plesiomonas identified as the dominant biomarker (LDA score = 5.32). Integrative networks identified these pathogenic genera as hubs linking metabolic dysregulation to liver damage. Collectively, combined cold–starvation induces synergistic liver injury via gut–liver axis disruption, driving metabolic reprogramming and oxidative damage. These findings provide candidate biomarkers for overwintering stress monitoring and inform management strategies to mitigate cold–starvation-induced hepatic injury in aquaculture. Full article

Dietary patterns increasingly influence research on neurodegenerative diseases, with attention shifting from isolated nutrients to integrative nutritional models. The Amazonian Diet, a biodiversity-based dietary pattern rich in native fruits, seeds, freshwater fish, and cassava-derived foods, is naturally enriched in bioactive compounds including polyphenols, anthocyanins, carotenoids, methylxanthines, selenium, vitamins, and unsaturated fatty acids. This review aimed to investigate the potential relevance of key foods derived from the Amazonian Diet to Parkinson’s disease (PD) by integrating compositional nutritional analysis, multivariate analytical approaches, and mechanistic evidence synthesis. In Stage 1, the composition of 36 Amazonian foods was analyzed using TBCA and FAO data, followed by hierarchical clustering analysis (Ward’s linkage, Euclidean distance). Distinct compositional patterns were identified, highlighting foods with high bioactive diversity, relevant lipid composition, and dietary fiber. In Stage 2, an integrative literature review (PubMed/MEDLINE, SciELO) of in vitro, in vivo, observational, and clinical studies suggested that açaí berry, guaraná, cocoa/cacao, camu-camu, and Brazil nuts contain nutrients and bioactive compounds that intersect with biological pathways implicated in PD, including oxidative stress, mitochondrial dysfunction, and neuroinflammation. However, this review does not evaluate the effects of the Amazonian Diet on PD incidence, progression, symptoms, levodopa response, or biomarkers. Full article

Reintroduction programmes are increasingly used to restore threatened freshwater fishes, yet evaluating their success remains challenging during the early stages of population establishment. Genetic monitoring is commonly used to assess diversity but rarely provides direct evidence of natural reproduction. Here, we investigated natural reproduction following reintroduction in the endangered Zingel asper, a benthic fish endemic to the Rhône River basin. Between 2006 and 2015, more than 25,000 captive-bred individuals from two source populations were released into the Drôme River (France). Using 54 microsatellite loci, we assessed genetic diversity, effective population size, relatedness and inbreeding, reconstructed parentage relationships, and evaluated admixture among source lineages through hybrid assignment analyses. Wild source populations differed markedly in genetic diversity and effective population size, whereas captive propagation reduced genetic diversity and increased relatedness and inbreeding. Despite these effects, the reintroduced population exhibited higher allelic richness than any captive cohort. Parentage analyses provided direct genetic evidence of natural reproduction by identifying individuals whose genetic origin could not be explained by the captive breeding pedigree. Hybrid assignment analyses independently confirmed admixture between source lineages. These results show how complementary genetic approaches can provide early evidence of reintroduction success and support adaptive management of threatened fish populations. Full article

To understand the adaptive evolution of endangered plateau freshwater fishes to environmental stress and to better explore the underlying mechanisms in Aspiorhynchus laticeps—a critically endangered fish endemic to the Tarim Basin, Xinjiang, China—a combination of ecological experiments and transcriptome sequencing (RNA-seq) technology was used to study the differences in gene expression patterns among individuals under different salinities and flow conditions. This experiment included four treatment groups (CON, H-SA-S, L-SA, L-SA-S). A. laticeps specimens with an average weight of 2.92 ± 0.62 g and a body length of 58.22 ± 5.10 mm were selected, with three biological replicates for a 96 h combined stress treatment. Moreover, the relationships between these differences and the aquatic environment were analyzed. A total of 1847 differentially expressed genes (DEGs), including 935 upregulated genes and 912 downregulated genes, were identified under different aquatic environment stress modes. GO and KEGG enrichment analyses revealed that TNF signal transduction, the NF-κB pathway, and metabolic regulation were significantly enriched among the DEGs (p < 0.05). High salinity–alkali stress significantly activates the TNF/NF-κB pathway, regulates MST1, LOC107702867, LOC113110979 and other genes to enhance the body’s resistance; water flow changes mainly regulate energy metabolism through genes such as NEHOM01_1600 and gptl. These findings provide an important scientific basis for the ecological adaptability, protection, and proliferation of endemic and endangered fish in China, as well as for germplasm innovation to address ecological deterioration in plateau fishes in alpine and arid areas. This study provides a molecular-level theoretical foundation for artificial habitat regulation and the conservation of endangered Aspiorhynchus laticeps populations in the Tarim River. Full article

Fish gut microbiota is essential for maintaining host physiological health but is constantly threatened by environmental chemicals. Diphenyl phosphate (DPhP), a major degradation product of organophosphate flame retardants and an environmental pollutant widely detected in aquatic ecosystems, is a chemical of emerging concern; however, few studies have addressed its effects on the gut microbiota. In this study, zebrafish were exposed to environmentally relevant concentrations of DPhP (0.8, 3.9, or 35.6 μg/L) from the embryonic stage to adulthood over 120 days. Using V3-V4 region 16S rRNA gene sequencing and functional gene prediction, we systematically analyzed the sex-specific responses of the gut microbiota. The results showed that life-cycle DPhP exposure exerts markedly different effects on the gut microbiota of male and female zebrafish. In females, DPhP induced concentration-dependent, stepwise Tax4Fun2 predicted functional shifts suggestive of compensation: at the low concentration (0.8 μg/L), energy metabolism and cofactor/vitamin metabolism functions were predicted to be enhanced; at the medium concentration (3.9 μg/L), Fusobacteria (mainly Cetobacterium ceti) became dominant, accompanied by structural remodeling; at the high concentration (35.6 μg/L), genetic information processing and amino acid biosynthesis pathways were upregulated, suggesting active substance synthesis. In contrast, the gut microbiota of male zebrafish did not exhibit significant changes in diversity but showed widespread predicted functional impairment. Core energy metabolism and cofactor/vitamin metabolism functions were significantly suppressed, while taxa associated with pro-inflammatory phyla (Proteobacteria, Verrucomicrobia) expanded. Functional compensation in males was limited to xenobiotic degradation and fatty acid metabolism, suggesting a potential pathological shift. These findings suggest a sex-differential response of DPhP from the perspective of the gut microbiota, providing new evidence for the environmental risk assessment of organophosphorus flame retardants. Full article

Microplastic pollution is an increasingly important environmental concern, especially in aquatic ecosystems. However, research on microplastics has historically been skewed towards marine systems and large freshwater systems, leading to an incomplete picture of the potential prevalence and scope of this type of pollution. In order to understand the potentially ubiquitous nature of freshwater microplastics, our study focused on 11 small headwater streams in north–central Massachusetts (USA) and a small freshwater fish species, the Blacknose dace (Rhinichthys atratulus). Microplastics were found in all sampled streams. Considerable variation in the number of stream microplastics existed, with concentrations ranging from 0.3 to 45.1 pieces per cubic meter of water. Microplastics were assessed in 14–20 fish from each of five of these streams. The vast majority of all fish had microplastics, with some individuals having over 200 pieces in their digestive tract. The number of fish microplastics was not found to be statistically related to the amount of water microplastics, the length of the fish, or the land use surrounding the streams. Together, these results illustrate that microplastics are prevalent and that small freshwater ecosystems need to be considered when assessing the full impact this source of pollution may have on ecosystems. Full article

Gold nanoparticles (AuNPs) are widely used in aptasensors because of their high extinction coefficient and aggregation-dependent color differences. However, recent studies have indicated that nonspecific interactions between target molecules and AuNPs may dominate the detection signal rather than aptamer–target specific binding. This study systematically investigated the interactions between 13 aminoglycoside antibiotics and AuNPs. We found that all aminoglycoside antibiotics interacted strongly with AuNPs, considerably reducing their salt stability. Furthermore, methoxy polyethylene glycol thiol reversed AuNP aggregation induced by aminoglycoside antibiotics, indicating that it occurs at the secondary minimum. Using density functional theory, we analyzed the molecular structures and charge distribution characteristics of the aminoglycoside antibiotics, elucidating that they replace citrate ions on AuNP surfaces via a ligand exchange mechanism, thereby inducing aggregation. Additionally, both aptamer targets and complementary DNA struggled to desorb the aptamer (KAN6-1) from the AuNP surfaces. Our study demonstrates that the label-free colorimetric assay based on aggregation of unmodified citrate–AuNPs is neither suitable for characterizing the binding affinity of aminoglycoside aptamers nor viable for constructing corresponding colorimetric sensors to detect this class of antibiotics. Thus, researchers should incorporate mechanistic verification and rigorous controls when employing this system to ensure reliable results. Full article

Seasonal variability and reproductive investment influence oxidative metabolism in fish; however, the relationship between reproductive dynamics and antioxidant responses in freshwater cyprinids remains insufficiently understood. This study investigated seasonal and biological factors affecting antioxidant biomarkers in the gonads of Capoeta umbla and Capoeta trutta inhabiting the Karasu River (Türkiye). A total of 152 individuals were examined between April 2023 and March 2024, and reproductive indices (total body weight, gonad weight, and gonadosomatic index) were evaluated together with oxidative stress biomarkers, including malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx). Multivariate analyses (PERMANOVA, SIMPER, and principal coordinate analysis) were used to determine the factors shaping oxidative responses. Females exhibited higher reproductive investment, while reproductive activity increased during spring and summer, accompanied by elevated MDA levels and antioxidant enzyme activities. PERMANOVA identified season as the primary factor explaining variation in oxidative biomarkers (p = 0.001), followed by reproductive parameters, and PCO revealed clear seasonal separation among groups. These findings indicate that oxidative balance in gonadal tissues is strongly associated with seasonal reproductive cycles and environmental variability in wild freshwater cyprinids. Full article

The genus Hemiculter includes closely related freshwater fishes widely distributed across East Asia, and several species are difficult to distinguish using external morphology alone. Mitochondrial markers have been widely used for species identification and phylogenetic inference in fishes, but single-gene approaches may be insufficient when nominal species show recent divergence, mitochondrial introgression, or taxonomic inconsistency. In this study, we newly assembled and characterized three complete mitogenomes of Hemiculter: H. leucisculus from Korea, H. leucisculus from Mongolia, and H. eigenmanni from Korea. The three mitogenomes contained the typical 37 mitochondrial genes and showed conserved genome organization, base composition, codon usage, and tRNA structures. Comparative analysis of concatenated 13 protein-coding genes revealed uneven sequence variability, with relatively high nucleotide diversity in ND2, ND1, ND6, and ND5. Pairwise K2P distances and phylogenetic analyses showed that the Korean and Mongolian H. leucisculus mitogenomes formed a distinct clade, evidencing that sequences assigned to H. leucisculus did not form a single consensus mitochondrial lineage. Barcode-gap overlap appeared to reflect discordance between current species assignments and mitogenomic relationships rather than the absence of informative barcode genes. These results indicate that Hemiculter mitogenomes are structurally conserved but informative for detecting lineage-level divergence and taxonomic inconsistency. Our findings suggest that the H. leucisculus–H. eigenmanni complex requires further integrative reassessment using broader sampling, voucher-based morphology, and nuclear genomic evidence. Full article

This study aimed to investigate the effects of salinity changes on serum biochemistry, hormonal profiles, splenic immune function, hepatic lipid metabolism and intestinal microbiota of the F₂ generation of Chinese sturgeon (Acipenser sinensis) under freshwater and seawater acclimation (15–23.2 psu) conditions. A 30-day indoor culture experiment showed that seawater acclimation only induced a declining trend in juvenile growth without statistical significance compared to the freshwater group (p > 0.05). The levels of triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), alkaline phosphatase (ALP) and albumin II (ALBII) in the freshwater group were markedly lower than those in the seawater group (p < 0.05), while alanine aminotransferase (ALT), aspartate aminotransferase (AST), high-density lipoprotein cholesterol (HDL-C) and total protein (TPII) showed no significant differences (p > 0.05). The serum triiodothyronine (T3) concentration was significantly higher, and chloride ion (Cl⁻) was lower in freshwater individuals (p < 0.05). Cortisol, testosterone, K⁺, Na⁺, Ca²⁺, thyroid-stimulating hormone and T4 remained unchanged between the two salinity environments (p > 0.05). In gill tissues, lipase (LPS) and fatty acid synthase (FAS) activities were lower, whereas lipoprotein lipase (LPL) activity was higher in the freshwater group (p < 0.05), and no obvious difference was observed in hepatic metabolic enzymes. The splenic complement C4 content was significantly decreased in freshwater sturgeon (p < 0.05), while splenic C3, IgM and serum immune indices showed no statistical differences. All alpha-diversity indices of intestinal microbiota were significantly higher in the seawater group (p < 0.05). At the phylum level, the intestinal flora in the seawater group was dominated by Proteobacteria (69.6%) and Fusobacteriota (14.9%), whereas Fusobacteriota accounted for 81.5% in the freshwater group. At the genus level, seawater samples exhibited richer microbial composition including Sphingomonas, Cupriavidus and Cetobacterium, while the freshwater microbiota was overwhelmingly dominated by Cetobacterium (81.5%). In conclusion, salinity significantly regulates serum biochemistry, hormone secretion, lipid metabolism, splenic immunity and intestinal microbiota of the F₂ generation of Chinese sturgeon. The freshwater environment benefits lipid metabolism, thyroid hormone levels, and growth performance, with a simplified intestinal microbial structure. Seawater acclimation maintains higher gut microbial diversity and immune homeostasis, but induces osmotic stress, restricts thyroid hormone secretion and redistributes energy supply, thereby inhibiting fish growth. This study provides a theoretical basis for salinity domestication and scientific culture management of Chinese sturgeon. Full article

Genome editing by the CRISPR/Cas9 system is widely used for production of gene-modified animals, including fish. However, efficient gene editing in fish cultured cells, in particular germline stem cells (GSCs), is challenging, likely due to the difficulty in transfecting these cells. The ricefield eel (Monopterus albus), a sequential hermaphroditic species, is a freshwater fish of significant economic value in China. In this work, we report a simple method that can achieve high gene editing efficiency in primary GSCs of fish species, including ricefield eel. High transfection efficiency (50–95%) is achieved in fish GSCs by using a microchannel-based cell transfection system. Gene editing efficiency of up to 60% in primary ricefield eel GSCs is achieved using an integrated CRISPR/Cas9 vector strategy. High gene editing efficiency is also achieved in gibel carp (Carassius gibelio) GSCs and the medaka spermatogonial stem cell line SG3, demonstrating the general applicability of our method. Our data suggest that efficient transfection is key to high gene editing efficiency in fish cultured GSCs. This study establishes an efficient and reliable gene editing system for fish GSCs, which may facilitate the creation of new germplasm of genetically difficult-to-breed fish by combining GSC transplantation with gene editing techniques. Full article