Comparative metabolomic analysis of Chinese mitten crab (Eriocheir sinensis) during the daily cycle

The circadian rhythm of aquatic animals has been a subject of research in a diverse range of studies. However, research on the circadian rhythm of the economically important crustacean Eriocheir sinensis is scarce although this species exhibits an obvious circadian rhythm. In this study, we applied liquid chromatography–mass spectrometry‐based metabolomics to identify key metabolites in the hepatopancreas of E. sinensis under the 24‐h circadian rhythm. Through comparative analysis of the metabolites obtained at different time points (06:00 vs. 12:00 h, 06:00 vs. 18:00 h, and 06:00 vs. 24:00 h), 431 differentially expressed metabolites were identified and classified. The Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the differentially expressed metabolites were enriched in some circadian rhythm‐related pathways, especially metabolic pathways related to nutrient digestion and absorption. Moreover, several pathways with high impact factors such as “Intestinal immune network for IgA production” were identified, and their functions were mostly related to immunity. This is the first study to identify the metabolites in the hepatopancreas of a crustacean through metabolomic analysis. It provides novel insights into the circadian rhythm of E. sinensis, which could benefit its culture and further increase its economic value.