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.

Abstract

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