Single-Cell Transcriptomic Landscape of the Gill in Hypoxia-Stressed Tachysurus vachellii (Richardson, 1846): Insights into Cell-Type-Specific Responses of Different Epithelial Cells and Erythrocytes

The study aims to construct a single-cell atlas of the gill of yellow catfish Tachysurus vachellii (Richardson, 1846) and to explore the response patterns of gill cells under acute hypoxia stress. In this study, we performed single-cell sequencing and histological observations of T. vachellii, gills. A total of 37,090 cells and 33 cell clusters were collected, and 18 cell types were identified. We found that three clusters of NECs have different functions, and in the gene enrichment results of MC differential expression during hypoxia and reoxygenation, we observed that MC may be regulated by non-neuronal neurotransmitter signals during hypoxia stress. There are also differences in cellular communication and transcription factors between different NECs and MCs. After acute hypoxia, the expression of tjp2 and lima1 in PVC was significantly upregulated, and there was no significant change in the number of erythrocytes. Observation of the organizational structure revealed that muscle, skin, and gill tissues were affected after hypoxia, resulting in changes in the flattened epithelial cells and MRC ultrastructure of the gill. This study provides single-cell atlas and data support for the acute hypoxia and reoxygenation model of fish gill tissue.