Description of Branchiobdella bulgariensis sp. n. (Branchiobdellida) from Bulgaria.

Branchiobdella bulgariensis sp. n. is described from the River Topolnitza near the village of Dushantzi, Bulgaria. The main morphological character distinguishing the new species from Branchiobdella parasita (Braun, 1805) is the form of the spermatheca with spermathecal ampulla consisting of almost spherical proximal part and a narrower cylindrical or bulb-like distal part. In contrast, B. parasita is characterised by oval spermatheca. Another feature distinguishing these two species from one another is the form of peristomium: in B. bulgariensis, the dorsal lip of peristomium has four lobes while, in B. parasita, the peristomium is "simple, thin-skinned" (Braun, 1805) and "bears eight micro-tentacles" (Henle, 1835). The only known host of B. bulgariensis sp. n. is Austropotamobius torrentium. The new species has been found so far at several sites in Bulgaria and unknown locality in Slovakia. An unusual character for the order Branchiobdellida is described, i.e. ontogenetic development of jaws of B. bulgariensis resulting in a different shape of these structures in specimens of different age. [ABSTRACT FROM AUTHOR]