First adult cyclophyllidean tapeworm (Cestoda) from teleost fishes: host switching beyond tetrapods in Africa.

Tapeworms (Cestoda) of the order Cyclophyllidea include over 3,000 species of intestinal parasites of tetrapods, especially birds and mammals including humans. However, adults of cyclophyllideans have never been found in bony fishes, even though hundreds of thousands of these hosts have been examined for parasites globally over more than 250 years. In the present paper, we report on a unique example of host switching of a tapeworm from birds to teleost fish in Africa. A new genus, Ichthyolepis (Cyclophyllidea: Dilepididae), is erected to accommodate Ichthyolepis africana n. sp., which is the first cyclophyllidean tapeworm that sexually matures in teleost fishes. The new species parasitises several freshwater elephantfishes (Mormyriformes: Mormyridae) including Marcusenius macrolepidotus (type host) in South Africa, Marcusenius senegalensis in Senegal, Mormyrus caschive, M. niloticus and Pollimyrus isodori in the Sudan, and Mormyrus kannume in Egypt. Ichthyolepis n. gen. is typified by a large musculo-glandular apical apparatus with rostellar pouch and a rostellum armed with robust hooks similar in size, but different in shape, deep, sandglass-shaped genital atrium, vaginal atrium and cirrus armed with tiny spines, thick-walled, subspherical cirrus sac, large, lobulated ovary occupying a large part of the median pre-equatorial field of mature proglottids, numerous testes filling almost entirely the postequatorial median field of proglottids, long and narrow, sleeve-like lateral uterine diverticula, and spindle-shaped eggs. Molecular phylogenetics considers Ichthyolepis as a member of the lineage consisting of dilepidids from swifts (Apodidae) in Africa. All fish hosts of the new tapeworm are bottom feeders, live in muddy biotopes and are insectivorous, which indicates that its intermediate hosts may be insect larvae.