Hepatospora eriocheir infection affects the fitness of adult Chinese mitten crabs in their non-native range

Abstract

For many invasive crustaceans, including the Chinese mitten crab (Eriocheir sinensis), the prevalence and impact of parasites in their introduced range remain largely unexplored. The microsporidium Hepatospora eriocheir was recently detected in mitten crabs across Europe, yet little is known about its physiological effects on its host. In this study, the influence of H. eriocheir infection on physiological biomarkers in adult mitten crabs collected from rivers in Germany and Belgium was experimentally investigated. We assessed metabolic rates (routine and maximum metabolic rate, aerobic scope), haemolymph glucose and lactate levels, and lipid content in the hepatopancreas. Infection prevalence reached 27% in adult mitten crabs from the Belgian population and 38% in individuals from the German population. Infected individuals showed a significantly reduced maximum metabolic rate and aerobic scope, while the routine metabolic rate remained unaffected. Glucose levels were lower in infected crabs both at rest and post-exercise, which indicates that energy reserves have dropped, whereas lactate levels showed no significant difference. The lipid content in the hepatopancreas was reduced, likely due to direct exploitation of host resources by the parasite and damage to hepatopancreatic tissue. Together, these patterns indicate an impaired energy metabolism, which may hamper energetically demanding activities such as migration and reproduction. The Chinese mitten crab is a catadromous species, and as the examined crabs were at the life stage when they commence a long-distance migration for their single reproductive event, infection by H. eriocheir may compromise their ability to complete this migration and successfully reproduce.