<i>Contramyzostoma bialatum</i> (Annelida: Myzostomida), a new genus and species of parasitic myzostome infesting comatulid crinoids

The external and internal morphology of a new genus and species of parasitic myzostome is described from the territorial waters of Singapore. Contramyzostoma bialatum, new genus and new species, infests the arms of the crinoid Comaster gracilis where it occurs in burrow-like integumental cavities. Contramyzostoma bialatum is characterized by a dorsal body field bearing all the external appendages (viz., five pairs of parapodia, four pairs of lateral organs, two pairs of cirri, and an ano-genital cone) and by two large wing-like body extensions. The digestive system comprises a pharynx included in an introvert, several salivary gland cells, a stomach from which originate two loop-shaped digestive tubules, and an intestine. All individuals examined were females possessing two ovaries and a branched oviduct. The infestation by C. bialatum produces significant modifications of the host epidermis and dermis