Assessing the effects of elevated temperature on the expression of hsp70, hsp90, igf1, igf2, gh and ghrelin in Nile tilapia (Oreochromis niloticus)

Abstract

Global climate change significantly influences environmental temperature, affecting fish growth, feeding patterns, and overall health. Understanding how fish respond to thermal changes is crucial, particularly for stress response, metabolism and growth in aquaculture. This study examines the effects of different acclimation temperatures on stress response and growth-related gene expression in Nile tilapia (Oreochromis niloticus). The research focused on the expression of heat shock proteins (hsp70 and hsp90), insulin-like growth factors (igf1 and igf2), growth hormone (gh) and ghrelin in juvenile Nile tilapia (O. niloticus) acclimated to 31°C (control), 34°C, and 37°C over 14 days. The results revealed that expression of hsp70 and hsp90 were significantly upregulated at 37°C in both male and female fish, indicating a pronounced stress response. In contrast, the expression of igf1, igf2 and gh was highest at 34°C, stimulating metabolic processes and promoting somatic growth. In comparison, significantly lower levels were observed at 37°C, suggesting an inhibitory effect of higher temperatures on growth-related processes. Expression of ghrelin followed a similar pattern to that of IGF and GH with higher levels at 34°C correlating with increased appetite and growth, but a decreased expression at 37°C, indicating reduced feeding activity due to thermal stress. These findings underscore the critical role of maintaining optimal temperatures in aquaculture settings and provide valuable insights into the physiological mechanisms underlying thermal adaptation in Nile tilapia, with implications for improving aquaculture practices and ensuring the health and productivity of farmed fish under varying environmental conditions.