[The effect of final host species on invasive activity of Sobolevicanthus gracilis (Cestoda, Hymenolepididae) oncospheres to intermediate hosts (Ostracoda)].

Two species of ostracods: Heterocypris incongruens and Cypridopsis vidua were used as experimental intermediate hosts for Sobolevicanthus gracilis, with Anas platyrhynchos dom. and Gallus gallus as the two experimental final hosts. Three series of fourth-fold passages: in hens, from hens to ducks, and back into hens--via ostracods--were accomplished. The fourth series of passages--in turn to ducks--was carried out for confirmation the results obtained. The index of infective activity was calculated for each experimental series. It has been stated that the infective activity of oncospheres to H. incongruens differed from final host species to species, being clearly higher in larvae from hens then from ducks. No differences of the index depended on final host species were noticed in relation to C. vidua. The possible explanations of the results are discussed.