[Clonal variability in longevity of the cercariae of Himasthla elongata (Trematoda: Echinostomatidae)].

The study was carried out on Himasthla elongata cercariae shed by infected Littorina littorea snails. The infected periwinkles were collected from the settlement with the low prevalence of H. elongata. As shown earlier with the use of AFLP (Amplified Fragment Length Polymorphisms) method, rediae groups in all the infected periwinkles of this settlement arise from the infection of a mollusc with a single miracidium. Therefore, the cercariae shed by an infected mollusc have the same genotype or, in other words, represent a clone. The LT50 (the time during which 50% of cercariae perish in the experimental dish) were measured experimentally for cercariae Himasthla elongata belong to different clones. The investigated parameter demonstrated a high level of interclonal variability. Two groups of cercarial clones were identified: one of them was characterized by the high level of intraclonal variability in LT50 and the second, by the low one. It is assumed that the observed heterogeneity may be stipulated by different degrees of mitotic recombinations during formation of different cercarial clones.