The oncomiracidia of the monocotylid monogeneans Dictyocotyle coeliaca and Calicotyle kroyeri

Abstract

The eggs of D. coeliaca have been cultured successfully and the free-swimming larva has been studied for the first time. The eggs have an incubation period which for monogeneans is exceptionally long (4–5 months at 10 °C). Apart from maintenance at a low temperature no other special conditions such as high hydrostatic pressure or washing to remove host body fluid are necessary for development. It is not necessary for the eggs to come into contact with host body fluid before development can begin.The oncomiracidium of D. coeliaca has no eyes, a well-developed pair of anterior median gland cells and a pair of hamuli. The oncomiracidium of C. kroyeri is similar to that of D. coeliaca except for the presence of two pairs of conspicuous pigmented eyes, poorly developed anterior median gland cells, the presence of an extra pair of gland cells at the posterior end of the body and the absence of hamuli.A comparison of the larval features of D. coeliaca and C. kroyeri has confirmed that these parasites belong to quite distinct species.