Comparative LC-MS based non-targeted metabolite profiling of the Chinese mitten crab Eriocheir sinensis suffering from hepatopancreatic necrosis disease (HPND)

Hepatopancreatic necrosis disease (HPND) is a newly emerged disease in the Chinese mitten crab, and has caused significant economic damage to crab farmers. However, the exact pathogenesis of crab HPND has not been elucidated. To understand the metabolic shifts in the pathogenesis of the disease, we used LC-MS for metabolite profiling of the hepatopancreas of crabs with HPND. Diseased (DC) and healthy crabs (HC) from the ponds with disease occurrence, and healthy crabs (HHC) from adjacent ponds free from HPND, were analyzed. Histopathologic characteristics and potential pathogens in the hepatopancreas of the healthy and diseased crabs were preliminary investigated. Cellular damage or necrosis, including cell swelling, rupturing, vacuole formation and nuclear fragmentation were observed in diseased crabs. Pathogen screening revealed that, Hepatospora eriocheir, a parasite which was ever deemed to be the agent of the disease before, was unlikely the cause of HPND. Partial least squares discriminant analysis (PLS-DA) score plots revealed a significant metabolic difference between DC and HC in positive ionization modes (R2 = 0.96807, Q2 = 0.74558), while HC and HHC were grouped closely together. Fourty-five differential metabolites were identified and used for further functional pathway analyses. Two potential pathogenic factors, including fatty acid metabolic abnormalities and high concentrations of propamocarb (a widely used pesticide in vegetables), were found to be likely associated with HPND in the Chinese mitten crab. The identified metabolites and regulation pathways, and screening of potential pathogens in diseased crabs, should provide useful information for the prevention of the disease in the future.