Impacts of light on gut microbiota in Chinese mitten crab (Eriocheir sinensis)

Photoperiod is an essential environmental factor that affects physiological activity and feeding behavior in crustaceans. The current study aimed to investigate the mechanism by which photoperiod influences gut bacterial community composition in the Chinese mitten crab (Eriocheir sinensis). In this study, high-throughput 16S rRNA sequencing was used to identify variations in E. sinensis gut bacteria under three different light: dark conditions (24 L:0 D, 0 L:24 D, and 12 L:12 D). Shannon and Chao1 indexes of community richness and diversity differed significantly between the complete light group and complete dark group on day 4, but these differences disappeared by day 6, suggesting that the gut bacterial community became disrupted on day 4, but adjusted to the new environment by day 6. Tenericutes and Proteobacteria were the dominant phyla under all conditions. Clostridium abundance increased significantly on day 6 under conditions of complete light and complete darkness. These data suggest that the biological clock of E. sinensis minimized changes in gut bacterial community composition under different light conditions. Considering that the gut bacterial community has profound effects on the host, understanding various mechanisms of its influence (including interactions with photoperiod) should be useful for improving E. sinensis aquaculture.