Polymorphism of larvae of the genus Aploparaksis Clerc, 1903 (Hymenolepididae)

The larvae of 12 cestode species of the genus Aploparaksis have been studied. In order to confirm the determination, the definitive hosts, birds, were experimentally infected with 5 species and the intermediate hosts, oligochaetes, with 6 species of cestodes. A great variability was observed in the morphology of tail appendix of cysticercoids belonging to five types of larvae. It is assumed that the polymorphism of larvae of the genus Aploparaksis results from the morphological adaptation to the development under arctic conditions.