Response of appetite-related genes in relation to the rearing water temperature in red spotted grouper (Epinephelus akaara)

Abstract

Growth of fish is controlled by various environmental factors, including water temperature (WT). WT is also a major factor that affects the eating behavior of fish. In this study, we studied the relationship between WT and expression profiles of factors involved in appetite regulation and digestion in red spotted grouper. Fish were divided into three groups with 30 fish per group and reared for 2 weeks in a recirculating system at three different WT (natural WT, 20 °C, and 25 °C). After 2 weeks, they were sacrificed immediately after food intake (+ 0 h), 3 h after (+ 3 h), 6 h after (+ 6 h), and 3 h before being fed the next day (- 3 h). Fish samples were obtained for analysis of mRNA expression levels of cholecystokinin (CCK), leptin A (LepA), leptin B (LepB), and neuropeptide Y (NPY) in the brain, liver, and intestine. Expression of CCK and NPY mRNA was significantly higher at 25 °C compared to that at natural WT and 20 °C, but no difference was observed for leptin. This suggests that the red spotted grouper shows characteristics typical of subtropical fish and has higher levels of feeding and digestion when reared at 25 °C water temperature condition.