Temperature‐Induced Expression Dynamics for the Stress, Appetite and Growth‐Related Genes in Nile Tilapia ( <i>Oreochromis niloticus</i> )

Global climate change significantly influences environmental temperature, affecting the feeding patterns, growth, and overall health of fish. Understanding how fish respond to thermal changes is crucial, particularly for growth and stress response in aquaculture. This study examines the effects of different acclimation temperatures on the expression of stress, appetite, and growth‐related genes in Nile tilapia ( Oreochromis niloticus ). Quantitative real‐time PCR method was employed to analyze the expression of genes for growth hormone ( gh ) from the pituitary, insulin‐like growth factors ( igf1 and igf2 ), ghrelin , and heat shock proteins ( hsp 70 and hsp90 ) from the liver of juvenile Nile tilapia acclimated to 31°C (control), 34°C, and 37°C for 14 days. Results revealed that the expression of hsp70 and hsp90 as well as the level of blood glucose were significantly upregulated at 37°C in both males and females, indicating a pronounced stress response due to higher acclimation temperature. Conversely, the expressions of gh , igf1 , and igf2 were highest at 34°C, stimulating metabolic processes and promoting somatic growth. In comparison, significantly lower expression of these genes was observed at 37°C, suggesting an inhibitory effect of higher temperatures on growth processes. Expression of ghrelin followed a similar pattern to that of GH and IGFs with higher levels at 34°C correlating with increased appetite and growth, but a decreased expression at 37°C, indicating reduced feeding activity resulting from 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 under varying environmental conditions.