On the role of paratenic hosts in the life cycle of the nematode Anguillicola crassus in the Vistula Lagoon, Poland

Anguillicola crassus is an Asian nematode accidentally introduced to Europe and parasitising the swimbladder of European eels. Planktonic copepods are the major intermediate hosts but the success of this parasites depends on small fishes, acting as paratenic hosts and transmitting the nematode to eels. The role played by cyprinids and percids in the life cycle of A. crassus in the Vistula Lagoon was analysed. A total of 2398 fish specimens (1091 percids and 1307 cyprinids) were examined within December 1994-March 1997. The presence of the nematode was recorded in zander (Sander lucioperca), European perch (Perca fluviatilis), ruffe (Gymnocephalus cernuus), carp bream (Abramis brama), ziege (Pelecus cultratus), and roach (Rutilus rutilus), the ruffe being the most heavily infected fish species. The present findings advance our knowledge on the biology A. crassus and will help to predict its spread to other bodies of water.