Ultrastructure of the proglottid tegument (neodermis) of the cestode Echinophallus wageneri (Pseudophyllidea: Echinophallidae), a parasite of the bathypelagic fish Centrolophus niger

Abstract

Ultrastructural data are provided on the tegument (or neodermis) of proglottids of the cestode Echinophallus wageneri Monticelli, 1890, the first representative of the family Echinophallidae (Pseudophyllidea), parasites of bathypelagic fish, studied using transmission and scanning electron microscopy. The surface of the ventral concave side of proglottids is covered with filiform microtriches about 1.7 microm long. Their glycocalyx, although very thick, is less extensively developed compared to that on digitiform microtriches localized on the dorsal side of the proglottids, which is also covered with filiform microtriches. The digitiform microtriches of the convex dorsal side are about 0.6 microm long, with a very short, rounded spine and the extraordinarily extensive glycocalyx seen as flocculent material. Short digitiform microtriches of E. wageneri seem to differ from microthrix types previously reported in other cestodes by transmission electron microscopy. The posterodorsal margin of all proglottids is typical in possessing a transverse band of large spiniform, tusk-shaped microtriches with a very long spine (approximately 13 microm in length), merged with filiform microtriches. Marked regional differences found in the morphology and distribution of microtriches on the proglottids of E. wageneri may be related to the different functions of the individual parts of the strobila because of the curling of the tapeworm body within the intestine of its fish host.