Two New Species of Echinobothrium (Cestoda: Diphyllidea) from Batoids off South Africa

Examination of the bycatch from a hake survey off the coast of South Africa in 2010 yielded new diphyllidean tapeworms from 2 species of batoids not previously examined for this cestode order. The spotted skate, Raja straeleni (Rajidae), was found to host Echinobothrium dorothyae n. sp., which differs in hook formula from 37 of its 43 congeners, and can be distinguished from the 6 remaining species in features such as length, number and arrangement of testes, and number of cephalic peduncle spines. The second new species, Echinobothrium dougbermani n. sp., was collected from the lesser guitarfish, Rhinobatos annulatus (Rhinobatidae). This species differs from all but 6 of its congeners in hook formula. With respect to these 6 species, it differs in numbers of cephalic peduncle spines, testes and proglottids, overall size, and ovary shape. Furthermore, it bears lateral hooklets that are more posterior in position relative to the apical hooks than is seen in most of its congeners. Scanning electron microscopy of these 2 species highlights ultrastructural differences that exist among diphyllideans, which, although their complete taxonomic distribution and function(s) are not yet understood, are interesting to consider. These are: the presence or absence of a spinithrix-lacking “V” shaped region on the medial distal bothrial surface, variation in spinithrix form from anterior to posterior on the proximal bothrial surface, and surface elaborations in the form of tiny, ridgelike structures of varying length that may or may not anastomose with one another. The relatively random nature of the selection of the skates and guitarfish hosts sampled here supports the notion that the small percentage of species in these genera that are currently known to host diphyllideans, and likely also their respective families Rajidae and Rhinobatidae, are likely a result of a lack of sampling.