The experiment was conducted to investigate the effects of feeding rates on growth performance, liver glycolysis, gluconeogenesis, glycogen synthesis, and glycogen decomposition in juvenile largemouth bronze gudgeon (Coreius guichenoti). A total number of 600 fish were randomly distributed into 12 cylindrical plastic tanks with 50 fish per tank and triplicate tanks per treatment. Fish were fed with 2%, 3%, 4%, and 5% feeding rates (body weight per day) three times day⁻¹ for 8 w. The results indicated that the feeding rates significantly increased the body weight, weight gain rate, and specific growth rate (p < 0.05), while showing no significant effects on the condition factor and survival rate (p > 0.05). The feed conversion ratio was significantly enhanced by the feeding rate (p < 0.05), although no significant differences were observed when the feeding rate exceeded 3% (p > 0.05). The plasma glucose levels in the 4% and 5% groups were significantly higher than those in the 2% and 3% groups. Compared with other groups, the 5% group significantly increased the crucial rate-limiting enzyme activities and mRNA levels of glycolysis (PFKL and PK) (p < 0.05), while showing no significant differences on enzyme activities (PC, PEPCK, and G6P) and mRNA (pepck and g6p) levels of gluconeogenesis (p > 0.05). In addition, the mRNA levels of hepatic glut2 and glut4 in the 5% group reached the highest levels (p < 0.05). When the feeding rate exceeded 3%, hepatic glycogen and lipid accumulation were significantly increased, leading to a fatty liver phenotype. Meanwhile, the mRNA level of liver glycogen synthetase (gysl) was significantly increased (p < 0.05), while no significant difference was observed in glycogen phosphorylase (pygl) (p > 0.05). In summary, under the conditions of this study, a feeding rate exceeding 3% significantly accelerated hepatic glycogen and lipid accumulation, which ultimately induced fatty liver formation.

This study investigated the effects of dietary vitamin E (DL-α-tocopherol acetate) supplementation on growth performance, biochemical indices, antioxidant capacity, and ovarian development in female Chinese sturgeon (Acipenser sinensis) broodstock. A total of 180 healthy second-generation individuals (initial weight: 72.63 ± 3.64 kg) were randomly distributed into three groups and fed isonitrogenous and isolipidic diets supplemented with 0 (V0), 1 (V1), or 2 (V2) g/kg vitamin E for 14 months. At the end of the trial, fish in the V2 group exhibited significantly higher final body weight, body length, and girth, demonstrating superior growth performance compared to the V0 and V1 groups (p < 0.05). Plasma antioxidant capacity was significantly enhanced in the V2 group, as indicated by elevated activities of catalase, superoxide dismutase, and total antioxidant capacity, alongside reduced levels of reactive oxygen species and malondialdehyde (p < 0.05). Biochemical analysis revealed that vitamin E supplementation significantly decreased plasma glucose, urea nitrogen, and alkaline phosphatase levels (p < 0.05), with the V2 group showing a notable increase in high-density lipoprotein cholesterol (p < 0.05). Ultrasonographic examination demonstrated that ovarian thickness in both transverse and longitudinal sections was significantly increased in the V2 group (p < 0.05). This morphological improvement was corroborated by significantly higher plasma levels of estradiol and vitellogenin in the supplemented groups, particularly in the V2 group. In conclusion, the current study revealed that dietary 2 g/kg vitamin E supplementation not only promoted growth performance and enhanced antioxidant capacity but also effectively stimulated ovarian development by modulating key reproductive hormones in female Chinese sturgeon broodstock.

Understanding the early life history of the endangered largemouth bronze gudgeon (C. guichenoti) is crucial for optimizing artificial rearing and conservation strategies. To provide a unified scientific basis for these efforts, this study characterized the ontogeny of C. guichenoti larvae from hatching to 30 days post-hatch (dph) by integrating analyses of allometric growth, digestive histology, and enzyme activities. Morphometric analysis revealed that total length increased exponentially with age. Positive allometric growth was observed in swimming organs (pectoral, dorsal, and caudal fins) and eye diameter, indicating a priority in developing locomotion and sensory capabilities for survival in lotic environments. Histological examination showed that the digestive tract became patent by 4 dph, and functional structures were established by 5 dph, coinciding with yolk sac absorption and the initiation of exogenous feeding. The digestive system reached near-adult maturity by 20 dph. Enzyme activity profiles showed that trypsin activity increased continuously, peaking at 30 dph, while amylase and alkaline phosphatase peaked at 20 dph. Lipase activity remained low until a slight increase at 30 dph. These results indicate that C. guichenoti larvae adopt a “locomotion-first” strategy, with the digestive system becoming functional at 5 dph and maturing by 20 dph. These findings collectively define the critical windows for artificial propagation, specifically guiding the timing of initial feeding and feed formulation.

Understanding yolk nutrient utilization during embryogenesis is critical for improving artificial propagation of endangered fish. Here, we integrated targeted metabolomics and transcriptomics to profile nutrient dynamics and molecular regulation in embryos of the endangered largemouth bronze gudgeon (Coreius guichenoti) at three key stages: fertilized egg, neurula, and tail bud. Egg membrane diameter showed a unique biphasic change (5.50 mm → 8.81 mm → 6.43 mm), which appears to reflect the large pelagic-egg strategy. Total amino acids declined during development, while essential amino acids (leucine, arginine) peaked at neurula, suggesting a critical period for protein synthesis and neural formation which is supported by up-regulation of ribosome biogenesis and Wnt/Hippo/Hedgehog pathways. Saturated fatty acids (particularly C16:0) decreased, consistent with preferential β-oxidation for energy in early embryos, whereas docosahexaenoic acid (DHA) and arachidonic acid (ARA) increased continuously (reaching 53.9% and 6.00% of total fatty acids at tail bud), with a parallel up-regulation of the elongase gene elovl2, marking a shift from energy production to structural accumulation for neural and retinal development. Transcriptomics identified 22,228 differentially expressed genes (DEGs) at neurula (vs. fertilized egg) and 9,796 DEGs at tail bud (vs. neurula); the tail bud stage was marked by enrichment of cardiac muscle contraction and multiple metabolic pathways, aligning with the onset of organogenesis. Notably, expression patterns of key metabolic genes (glud1, phgdh, fasn, elovl2) corresponded with changes in their associated metabolites (glutamate, serine, DHA), offering supporting evidence for metabolic reprogramming. These findings provide a theoretical basis for optimizing broodstock diets (particularly DHA/ARA and essential amino acid supplementation), thereby supporting conservation aquaculture of Coreius guichenoti.

The stagnation of ovarian development at stage II in most captive broodstock hinders the artificial propagation of Chinese sturgeon (Acipenser sinensis). This study investigated the effects of dietary protein level and quality on ovarian development and the underlying metabolic mechanisms. Two experimental diets containing 42% (CP42) and 48% (CP48) crude protein, formulated with white fishmeal, and a commercial 48% protein diet (Control) were fed to 11+-year-old females with stage II ovaries for 12 months. After 12 months, fish fed CP48 showed greater ovarian thickness, body weight and girth, higher serum estradiol, total antioxidant capacity, superoxide dismutase activity and total protein, and lower triglyceride, glucose and malondialdehyde levels than the control (P < 0.05). Serum metabolomics showed that, compared with CP42, CP48 up-regulated eicosanoids (thromboxane B2 and 14-prostaglandin J2) in the arachidonic acid pathway; compared with the control, amino acids, peptides and analogues constituted the largest category of differential metabolites, and phosphatidylcholines and progesterone derivatives in the glycerophospholipid, α-linolenic acid and steroid hormone biosynthesis pathways were up-regulated. These findings indicate that a 48% protein diet with an amino acid profile balanced against stage II ovaries promotes steroidogenesis and nutrient accumulation, facilitating the ovarian development of Chinese sturgeon broodstock.