Forked Tail of the Cercaria of Schistosoma mansoni—a Rowing Device

Abstract

THE swimming motions of the cercaria of Schistosoma mansoni have been analysed by high-speed photography, at a rate of 500–800 pictures/sec. When cercariae swim backwards the two branches of the forked tail are spread out (Fig. 1a and b), while in forward-swimming cercariae the branches are close together (Fig. 1c and d). Without significantly altering the stroke rate of the tail, cercariae can change from backward swimming to forward swimming, or the reverse, depending on how they align the branches of the tail. When changing from backward swimming to forward swimming the cercaria lengthens its body by 30–40 per cent (Fig. 1c and d) and at the same time makes itself narrower.