Metabolomic analysis of coelomic fluids reveals the physiological mechanisms underlying evisceration behavior in the sea cucumber Apostichopus japonicus

Evisceration is a peculiar behavior that happens frequently in the processes of aquaculture and transportation of sea cucumbers. This behavior involves a complex physiological process and results in the expulsion of the digestive tract and other viscera. However, studies on evisceration are insufficient, and the identification of the internal regulatory metabolites and potential pathways of evisceration in the sea cucumber are therefore likely to provide a scientific basis for this specific behavior. In this study, ultraperformance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was performed on the coelomic fluids that ejected by evisceration Apostichopus japonicus and in the coeloms of normal A. japonicus to detect changes in metabolites and metabolic pathways in the process of evisceration behavior. In total, nine metabolites were found to have increased and eleven to have decreased in the ejected coelomic fluids of evisceration sea cucumbers. These metabolites included phosphatidylethanolamine, glucosylceramide, L-tryptophan, carbamic acid, and cyclohexylamine. In addition, enrichment of metabolic pathway analyses revealed five significantly changed signaling pathways: Glycosyl-phosphatidyl-inositol (GPI)-anchor biosynthesis, regulation of autophagy, sphingolipid metabolism, nitrogen metabolism, and phenylalanine, tyrosine and tryptophan biosynthesis. These results contribute valuable data on the potential physiological mechanisms underlying evisceration behavior of A. japonicus, which could have important implications for the aquaculture and transportation of sea cucumbers.