Studies on the Functional morphology of the Scolex and of the Genitalia in Echinobothrium brachysoma Pintner and E. affine Diesing from Raja clavata L.

Abstract

1. Echinobothrium brachysoma Pintner and E. affine Diesing have been found in the spiral valve of Raja clavata L. off the coast of Britain.2. The spiral valve is lined by tubular crypts into which the scolices of the worms are thrust, the strobila, with one gravid proglottid, being free in the lumen.3. The functional morphology of the scolex of E. brachysoma has been described. That of E. affine appears to be similar.4. The scolex adheres, mainly, by the apical hooks which can be raised by inner and outer elevator muscles attached to their roots and closely associated with the rostellum.5. The rostellum can be protruded by the contraction of a dorsal and a ventral protractor muscle. Movements of the rostellum elongate the scolex in a dorsoventral direction, forcing the apical hooks against the crypt wall and supporting them.6. The peduncle hooks are not often embedded in the epithelium. Both series of hooks damage the epithelial lining of the crypt.7. The remaining musculature, excretory and nervous systems are described.8. The genitalia are essentially the same in both species. The number of testes varies from one proglottid to another in the same worm. In E. brachysoma the mid-ventral genital atrium is near the posterior end which affects the course of the vagina. The eggs in both species include two yolk cells which are similar to those of the Digenea and Pseudophyllidea.