Seussapex, a new genus of lecanicephalidean tapeworm (Platyhelminthes: Cestoda) from the stingray genus Himantura (Myliobatiformes: Dasyatidae) in the Indo-West Pacific with investigation of mode of attachment.

A new lecanicephalidean genus, Seussapex gen. n., is erected for specimens collected from stingrays from the Indo-West Pacific resembling the little known species Tenia [sic] narinari MacCallum, 1917 from the spotted eagle ray, Aetobatus narinari (Euphrasen). Members of this new genus are unique in their possession of a multi-tiered apical structure comprising a bipartite apical modification of the scolex proper, and an externally bipartite apical organ with anterior and posterior glandular compartments internally. The appearance of the scolex varies dramatically depending on state of protrusion and/or evagination of these different parts which appear to be able to function independently. Seussapex karybares sp. n. parasitizing Himantura uarnak 2 (sensu Naylor et al., 2012) in northern Australia is described as the type species and Tenia [sic] narinari is transferred to the new genus. The two species differ in scolex length and width of the posterior dome-shaped portion of the apical organ. Histological sections of scoleces stained using the periodic acid-Schiff(PAS) reaction showed the surface of the anterior part of the apical organ and the anterior glandular compartment to stain PAS positive, suggesting a chemical mode of attachment to the host's intestinal mucosal surface. Extensive collecting efforts of stingrays in the Indo-West Pacific shows Seussapex gen. n. to be restricted to species of Himantura Miller et Henle and suggests additional diversity in this group of hosts. In addition, the host identity of Seussapex narinari (MacCallum, 1917) comb. n. is called into question.