A New Onchoproteocephalidean Cestode Species from the Spot-Tail Shark, Carcharhinus sorrah (Müller et Henle), in the Persian Gulf

A new species of Phoreiobothrium Linton, 1889 (Cestoda: Onchoproteocephalidea) from the spinner shark, Carcharhinus brevipinna (Valenciennes) off the coast of KwaZulu-Natal, South Africa

The extreme sparsity of collection efforts in many parts of the word, including southern Africa, leaves a vast hidden diversity of marine cestode species, such as species of Phoreiobothrium. The examination of a common South African coastal-pelagic shark species, Carcharhinus brevipinna (Valenciennes), resulted in the discovery of a new species of Phoreiobothrium Linton, 1889. Phoreiobothrium martini sp. n. is undoubtedly different from all other congeners in several morphological characteristics, however, it is most easily distinguished from other species by its total length, the size of its hooks, and the number of post vaginal testes. The addition of P. martini sp. n. increases the total number of valid species of Phoreiobothrium to 20 worldwide. Furthermore, P. martini sp. n. marks the description of representatives of only the second onchoproteocephalidean genus from southern Africa, therefore expanding the generic biogeographical representation and introducing new host associations. Apart from the description of this new species of cestode, the discovery of additional species of Phoreiobothrium will be beneficial regarding future ecological investigations. With the high degree of host-specificity found amongst species of Phoreiobothrium, species such as P. martini sp. n. could be used as sentinel species for the accurate identification, separation and diagnosis of commonly misidentified shark species.

Two New Cestode Species of Phoreiobothrium (Onchoproteocephalidea) from Two Carcharhinid Sharks of the Persian Gulf, with the First Report of Variation in Distribution of Vitelline Follicles of the Genus

PURPOSE

The aim of this work was the morphological study of the onchoproteocephalidean cestodes from two shark species of the Persian Gulf.

METHODS

Several specimens of Rhizoprionodon oligolinx, as well as of Carcharhinus dussumieri, were collected from the Persian Gulf, and the isolated cestodes from them were studied morphologically by light and scanning electron microscopy.

RESULTS

Phoreiobothrium sarahae n. sp. and Phoreiobothrium iraniense n. sp. were isolated, respectively, from Rhizoprionodon oligolinx Springer and Carcharhinus dussumieri (Müller & Henle). Both species are quite distinct from their congeners, except for P. sorrahcola Masoumi Ganjgah & Haseli, 2020, in the distribution of the vitelline follicles (i.e., having more than two columns of vitelline follicles in each lateral band in the proglottids) and are distinguished from each other based on measurement, e.g., by the length of the cephalic peduncle, the width of the scolex at the level of hooks, and some measures related to the hooks. Phoreiobothrium iraniense n. sp. most closely resembles P. sorrahcola, earlier described from C. sorrah (Müller & Henle) from the Persian Gulf, with which it has an extensive overlap in the ranges of measurements and morphology. Nonetheless, it differs from P. sorrahcola in the length of the cephalic peduncle and possessing, rather than lacking, the gladiate spinitriches on the proximal bothridial surfaces.

CONCLUSION

Along with the description of the two new species increasing the number of members of the genus in the Iranian coastal waters from three to five, for the first time a variation in distribution of the vitelline follicles is reported for Phoreiobothrium in this paper.