Two new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) from Pastinachus cf. sephen (Myliobatiformes: Dasyatidae) from the Persian Gulf and Gulf of Oman.

Two new species of Acanthobothrium van Beneden, 1850 from the spiral intestine of Pastinachus cf. sephen Forsskål from the Iranian coast of the Persian Gulf and the Gulf of Oman are described. To analyse the surface ultrastructure the worms were studied using light and scanning electron microscopy. Acanthobothrium jalalii sp. n. belongs to the category 1 species of the genus so far including 43 species. This tiny new species differs from the other category 1 species by its small total length (2.18 +/- 0.49 mm), number of proglottids (4.7 +/- 0.9) and testes (24 +/- 3), terminal segments in an apolytic condition and the shape of the cirrus-sac. Acanthobothrium sphaera sp. n. is a small worm that belongs to the category 2 species of the genus so far including 36 species. A. sphaera sp. n. differs from the other category 2 species by its small total length (1.6 +/- 0.2 mm), number of proglottids (9.6 +/- 1.2) and testes (12 +/- 1), the presence of a vaginal sphincter and the shape of the ovary. This is the first report of Acanthobothrium from the cowtail stingray, P cf. sephen, from the Persian Gulf and Gulf of Oman. Pastinachus sephen sensu lato has been reported as a common host of species of Acanthobothrium. Most recently, the host genus Pastinachus Rüppell has been split into five nominal species and several Acanthobothrium species infect the newly described congeners but not P. sephen. The real identity of the host studied within the present study is still in question, since sequence data of three specimens from the Gulf of Oman do not correspond to P. sephen sensu stricto.