Position, structure and function of pulsatile vesicles in parasitic leeches Codonobdella truncata Grube, 1873 and Caspiobdella fadejewi Epshtein, 1961 [Hirudinea, Piscicolidae, Piscicolinae]

Histological analysis of frontal section through the body of parasitic leeches (Codonobdella truncata, Caspiobdella fadejewi) of the subfamily Piscicolinae revealed the presence of 11pairs of subepidermal pulsatile vesicles. The vesicles of C. truncata are poorly visible on the body surface, contrary to those of C. fadejewi, which results from the fact that in the former species the vesicles are located in a layet of subepidermal connective tissue thicker (82.82 μm) than in C.fadejewi (20.6 μm). In the studied species the pulsatile vesicles have a club-like shape, are surronded by a muscular tunicle and connected with a short canal that penetrates the body wall. Some of the sections show that the vesicles are divided in two chambers (lower and upper) with an incomplete membrane.