A new genus of Phyllobothriidae (Cestoda: Tetraphyllidea) in carcharhiniform sharks from Iran and Australia

The collection of cestodes from the carcharhiniform shark Carcharhinus cf. dussumieri in the Persian Gulf off Iran resulted in the discovery of the new genus and species of tetraphyllidean tapeworm, Doliobothrium haselii n. gen. n. sp. Collections from the carcharhiniform shark Rhizoprionodon acutus in the Timor Sea off northern Australia resulted in material that is consistent with a species originally described as Pithophorus musculosus from this host species in India, but that appears to represent a second species in the new genus. This second species is redescribed and transferred to Doliobothrium n. gen. The two species differ from one another in total length, testis number and total number of proglottids, with the latter species generally being smaller in overall size than the former species. Histological sections and scanning electron microscopy confirm that this new genus differs from all other phyllobothriid genera in the possession of bothridia that both lack apical suckers and are tubular in form, bearing proximal and distal apertures. Despite differences in scolex morphology, the proglottids of the new genus are remarkably similar to those seen in Orectolobicestus, Paraorygmatobothrium and Ruhnkecestus, all of which also parasitize sharks. These four genera also share the presence of serrate gladiate spinitriches on their proximal bothridial surfaces. This is only the second report of a cestode from an elasmobranch from the Persian Gulf. Limited available data suggest that the fauna of this region resembles that of other regions of the Indo-Pacific. Furthermore, owing to the paucity of available information and specimens, it is recommended that Pithophorus and three of its remaining described species (i.e. P. pakistanensis, P. trygoni, P. yamagutii) be considered as a genus inquirendum and species inquirenda, respectively.