Vitellogenesis in fish represents a critical phase of oogenesis, significantly influencing the nutritional provisioning for oocyte maturation and subsequent offspring development. However, research on the physiological mechanisms governing vitellogenesis at the single-cell level remains limited. In this study, we performed single-nucleus RNA sequencing (snRNA-seq) on the ovaries of Sichuan bream (Sinibrama taeniatus). We first identified six distinct cell types (germ cells, follicular cells, immune cells, stromal cells, endothelial cells, and epithelial cells) in the ovaries based on typical functional marker genes. Subsequently, we reconstructed the developmental trajectory of germ cells using pseudotime analysis, which describes the transcriptional dynamics of germ cells at various developmental stages. Additionally, we identified transcription factors (TFs) specific to germ cells that exhibit high activity at each developmental stage. Furthermore, we analyzed the genetic functional heterogeneity of germ cells and follicular cells at different developmental stages to elucidate their contributions to vitellogenesis. Finally, cell interaction analysis revealed that germ cells communicate with somatic cells or with each other via multiple receptors and ligands to regulate growth, development, and yolk acquisition. These findings enhance our understanding of the physiological mechanisms underlying vitellogenesis in fish, providing a theoretical foundation for regulating ovarian development in farmed fish.

Background: The Fujiang River, a first-order branch of Jialing River, has for years been separated into six segments by six cascading hydropower stations in its downstream. However, the impact of cascading hydropower stations on its aquatic biota communities remains unclear. Methods: eDNA samples were collected in the upper, middle, and lower reaches of each river fragment during March, May, July, and December 2023, and after species identification, various statistical analyses including β-diversity, NMDS and MantelTest were performed using the R platform. Results: A total of 82 fish species belonging to 15 families were identified. The fish communities in the six fragments of the downstream Fujiang River showed a high degree of overlap, and a notable aggregation of fish communities between the upper, middle, and lower areas within each river section was also observed. Flow velocity (FV) and water temperature (TEMP) were found to be important factors in shaping fish distribution. Conclusion: Fish composition and distribution trend towards homogenization in the downstream of the Fujiang River.