In recent years, bisphenol AF (BPAF) in aquatic environments has drawn attention to its ecological risks. This study aims to investigate the toxic effects of BPAF (188.33 μg/L) exposure for 30 days on female marine medaka (Oryzias melastigma). On the 10th and 30th day of exposure, the toxicity was evaluated using histological analysis of the liver and ovaries and the transcription levels of genes related to the antioxidant system, immune system, and hypothalamic-pituitary-gonadal (HPG) axis. Findings revealed that (1) BPAF exposure caused vacuolation, karyopyknosis and karyolysis in the liver of marine medaka, and the toxic impact augmented with duration; (2) exposure to BPAF for 10 days facilitated the growth and maturation of primary ova, and this exposure had a comparatively inhibitory effect after 30 days; (3) exposure to BPAF resulted in a biphasic regulation of the transcriptional abundance of genes involved in antioxidant and inflammatory response (e.g., il-8, cat), with an initial up-regulation followed by down-regulation. Additionally, it disrupted the transcriptional pattern of HPG axis-related genes (e.g., 3βhsd, arα). In conclusion, 188.33 μg/L BPAF can alter the expression levels of functionally related genes, impair the structural integrity of marine organisms, and pose a threat to their overall health.

The Naozhou stock of large yellow croakers (Larimichthys crocea) exhibits unique phenotypic traits and high genetic diversity, making it a valuable resource for selective breeding and genetic conservation in aquaculture. Despite its importance, simple sequence repeat (SSR) markers have not been developed for this stock, which limits efforts in genetic evaluation, breeding optimization, and sustainable utilization of this commercially important species. In this study, 195,263 SSRs were identified from the genome of the Naozhou stock of large yellow croaker, covering a total length of 16,578,990 bp with a density of 288 bp/Mb. Dinucleotide repeats were the most common, with the AC motif being the most prevalent. The frequency of SSR markers ranged from 245.63 to 346.60 per Mb. A total of 30 primer pairs were synthesized, of which 28 pairs (93.3%) successfully amplified clear and reproducible bands in PCR assays. Among these, 28 SSR markers exhibited distinct and reproducible bands following gel electrophoresis. For eight SSR loci, the number of alleles (Na) ranged from 4 to 22 (mean = 11.375), while the effective number of alleles (Ne) ranged from 1.5401 to 10.4727 (mean = 5.6475). The assembled mitochondrial genome (mtDNA) was 16,467 bp in length and comprised 37 genes, including 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The total sequence length of the PCGs was 11,431 bp, accounting for 69.4% of the mtDNA. A large portion of the PCGs (5) used incomplete stop codons (e.g., nad2, nad3, cox2), while others used TAA stop codons (e.g., nad6, nad5, TrnT). The mtDNA encoded a total of 3808 codons, with UAA showing the highest relative synonymous codon usage value. The SSR markers and mtDNA data generated in this study provide valuable tools for future genetic breeding and genomic research on the Naozhou stock of large yellow croakers.

This study examined the digestive and metabolic responses of Naozhou (NZ) stock large yellow croaker (Larimichthys crocea) larvae and juveniles under five developmental feeding stages (DAH3, DAH7, DAH12, DAH19, DAH49) to clarify mechanisms of early nutritional adaptation. Digestive enzyme assays, transcriptome sequencing, and metabolomics were integrated to compare physiological changes across diets. Protease activity increased sharply from DAH7–19 with the introduction of rotifers, Artemia, and copepods, while amylase and lipase activities rose at DAH19–49, reflecting enhanced carbohydrate and lipid utilization during transition to formulated feeds. Transcriptomic analysis showed that differentially expressed genes were enriched in pathways involving protein digestion, lipid and energy metabolism, and cell cycle regulation. The metabolomic analysis further highlighted dynamic changes in amino acid, lipid, carbohydrate, and vitamin metabolism, consistent with transcriptomic findings. The integrated analysis suggests that the coordinated modulation of digestive enzyme activities, gene expression, and metabolite profiles enabled a smooth transition from yolk dependency to live prey feeding and a subsequent use of artificial diets. These findings provide new insights into the early nutritional development of NZ large yellow croaker and provide a scientific basis for the improvement of artificial aquaculture seed production.

Nitrite accumulation in aquaculture environments poses a critical threat to fish health, particularly affecting sensitive physiological systems such as the gut. This study investigated the intestinal stress response of juvenile four‐finger threadfin ( Eleutheronema tetradactylum ) under nitrite exposure through integrated analyses of intestinal microbiota and metabolomics. Acute toxicity tests revealed that nitrite has a time‐ and dose‐dependent effect, with a 96‐h LC ₅₀ of 4.95 mg/L and a safe concentration estimated at 0.50 mg/L. Under nitrite stress, significant alterations were observed in the intestinal microbial community structure, notably a shift in the abundance of dominant genera such as Vibrio , Photobacterium and Bacillus . Although alpha diversity indices did not show significant variation, beta diversity analyses highlighted distinct microbial compositions among control, stress and recovery groups. Functional prediction using FAPROTAX suggested that nitrite stress altered microbial activities related to chemoheterotrophy and nitrate reduction. Metabolomic profiling identified substantial shifts in metabolite levels, with key enrichments in ABC transporter and aminoacyl‐tRNA biosynthesis pathways during stress and recovery, respectively. Enzyme assays further revealed that nitrite stress caused dynamic changes in intestinal amylase, lipase and trypsin activities, with partial recovery post‐exposure. The integration of microbial and metabolic data demonstrated strong correlations between specific microbial taxa and metabolites, suggesting coordinated host–microbe responses under nitrite‐induced oxidative and metabolic stress. These findings provide comprehensive insights into the gut‐level impact of nitrite toxicity and identify key microbial and metabolic biomarkers involved in stress adaptation and recovery. The study underscores the importance of nitrite monitoring and management to ensure intestinal health and sustainable aquaculture of E. tetradactylum .