Artificial Infection of the European Eel with Third-Stage Larvae of the NematodeAnguillicola crassus

Abstract

We conducted an experiment on the migration of larvae of the nematode Anguillicola crassus in European eels Anguilla anguilla during an artificial infection. Three hundred young (1-g) elvers were fed the copepod Paracyclops fimbriatus infected with nematode larvae. At different time intervals, groups of 10 eels were sampled and preserved in Bouin Hollande for histological survey. The last sampling took place six months after the infection. The nematodes used a direct migration route through the intestinal wall and body cavity into the swim bladder. Within 17 h after infection, migrating larvae had already reached the swim bladder. Within 3 months after infection, the next larval stage was found. Preadult larvae were found within 4 months after infection. Our experimental results generally agree with findings on the life cycle of Anguillicola spp. in Japanese eels Anguilla japonica. However, the parasite can show aberrant migration paths in European eels. The pathological phenomena after this single experimental infection appeared less severe than after natural infections.