Effects of Light and Feeding on Expressions of Clock Genes and Metabolic Genes in the Ridgetail Shrimp, Exopalaemon carinicauda

Abstract

The changes of the circadian clock genes expression, growth, and muscle composition in Exopalaemon carinicauda under different photoperiods and feeding time were investigated by real-time fluorescence quantitative PCR and muscle biochemical composition analysis, respectively. Results showed that four clock genes of Clock, Cry1, Tim, and Per2 showed significant circadian rhythms in both eyestalk and hepatopancreas. Their expression rhythms were highly correlated with the photoperiod in the eyestalk, but in the hepatopancreas, it was significantly correlated with the feeding time. Moreover, the expressions of several metabolic genes were also variable; adipose triglyceride lipase (ATGL) and amyloglucosidase (AGL) changed significantly with the shift of feeding time, whereas methionine synthase (MS) and succinate dehydrogenase (SDH) changed significantly with the photoperiod. This reflected the close relationship between the metabolic and circadian clock in E. carinicauda; Alterations in photoperiod or feeding time lead to changes in the biological clock systems, which affects the daily expression of metabolic genes at the downstream metabolic pathway and closely correlates their expression rhythms with epi-environmental factors such as feeding. It can be seen from the results that the feeding was also a significant factor that affected the crude protein and crude fat contents in muscle tissue of E. carinicauda; their highest values (18.69% ± 0.13%, 1.81% ± 0.02%) were also occurred in the treatment with feeding at 19:00. Differences in muscle composition through a similar mechanism of action, i.e., the biological clock system are affected by the feeding and then regulated changes in downstream metabolic processes. As a result, the optimized conditions for the cultivation of E. carinicauda were a short light-phase photoperiod (8L : 16D) with feeding after sunset (19:00).