MORPHOLOGY AND CHAETOTAXY OF ECHINOCHASMUS SP CERCARIA (TREMATODA, ECHINOCHASMIDAE)

Gymnocephalous zygocercous cercariae were shed by naturally infected snail prosobranch Hydrobiidae: Bithynia tentaculata, collected in Lithuania. Their morphology is described; they are closely related to that of several species of Echinochasmus, mainly displaying two subegal spiny suckers, excretory ducts with 15-20 large granulations, a double excretory vesicle, 16 flame cells and allow the generic determination as Echinochasmus sp. The chaetotaxy is completely carried out and shows a peculiar disposition in C(II), C(IV), S and U levels; in C(II), C(IV)5 and S levels the sensillae reveal a relationship with Psilostomidae, in U level, the sensillae are different. Echinochasmus genus seems to belong to a valid family Echinochasmidae, as proposed by Sudarikov and Karmanova (1977). This family appears more closely related to Psilostomidae than to Echinostomatidae.