Trypanorhynch cestodes from elasmobranchs from the Gulf of Oman, with the description of Prochristianella garshaspi n. sp. (Eutetrarhynchidae).

In a study on the order Trypanorhyncha Diesing, 1863, a total of 35 specimens belonging to nine species of elasmobranch in the Gulf of Oman, was examined. The following trypanorhynch species were identified: Pterobothrium lesteri Campbell & Beveridge, 1996, Otobothrium carcharidis (Shipley & Hornell, 1906), Eutetrarhynchus platycephali Palm, 2004, Parachristianella indonesiensis Palm, 2004, Pa. monomegacantha Kruse, 1959 and Prochristianella mooreae Beveridge, 1990. Prochristianella garshaspi n. sp. is described from Pastinachus sephen (Forsskål) and Rhinoptera sp. The new species is allocated to the genus Prochristianella Dollfus, 1946 on the basis of the presence of two bothria, prebulbar organs, and a heteroacanthous typical tentacular armature with relatively few hooks in each principal row, hollow hooks increasing in size from antibothrial and then decreasing towards the bothrial surface of the tentacle, hooks 1 and 1' being separated, and a basal swelling with characteristic billhooks increasing in size towards the bothrial surface. The lack of microscopically visible microtriches on the scolex distinguishes the new species from P. hispida (Linton, 1890), P. clarkeae Beveridge, 1990, P. thalassia (Kovaks & Schmidt, 1980), P. multidum Friggens & Duszynski, 2005 and P. cairae Schaeffner & Beveridge, 2012. Prochristianella garshaspi n. sp. can be distinguished from the remaining species within the genus by a combination of the following morphological features: the presence of numerous gland-cells within the tentacular bulbs, the number of rows on the basal swelling, the number of hooks per half spiral row, the size of the principal hooks, the number of the testes and the presence of an external seminal vesicle.