Transcriptomic Analysis on the Effects of Altered Water Temperature Regime on the Fish Ovarian Development of Coreius guichenoti under the Impact of River Damming

Field investigation indicated that the reduction in fish spawning was associated with the alteration in water temperatures, even a 2-3 degrees C monthly difference due to reservoir operations. However, the physiological mechanism that influences the development of fish ovary (DFO) remains unclear. Thus, experiments of Coreius guichenoti were conducted at three different temperatures, optimal temperature (similar to 20 degrees C, N) for fish spawning, lower (similar to 17 degrees C, L), and higher (similar to 23 degrees C, H), to reveal the effects of altered water temperature on the DFO. Comparisons were made between the L and N (LvsN) conditions and H and N (HvsN) conditions. Transcriptomic analysis differentially expressed transcripts (DETs) related to heat stress were observed only in LvsN conditions, indicating that the DFO showed a stronger response to changes in LvsN than in HvsN conditions. Upregulation of DETs of vitellogenin receptors in N temperature showed that normal temperature was conducive to vitellogenin entry into the oocytes. Other temperature-sensitive DETs, including microtubule, kinesin, dynein, and actin, were closely associated with cell division and material transport. LvsN significantly impacted cell division and nutrient accumulation in the yolk, whereas HvsN only influenced cell division. Our results highlight the impact of altered water temperature on the DFO, thereby providing insights for future reservoir operations regarding river damming and climate change and establishing fish conservation measures.

Automated summary

Field investigation revealed that alterations in water temperatures, even as little as a 2-3 degrees C difference due to reservoir operations, were associated with a reduction in fish spawning. However, the underlying physiological mechanism remains unclear. In order to investigate the effects of altered water temperature on fish ovary development, experiments were conducted on Coreius guichenoti at three different temperatures. The results showed that the DFO had a stronger response to changes in lower temperature conditions compared to higher temperature conditions. Upregulation of certain genes related to vitellogenin receptors was observed at the normal temperature, indicating that it facilitated the development of fish ovary. Other temperature-sensitive genes were found to be associated with cell division and material transport. The findings provide valuable insights for reservoir operations and fish conservation measures in the face of river damming and climate change.