Two new species of Phoreiobothrium Linton, 1889 (Cestoda: Onchoproteocephalidea) off southern Iran, completing the puzzle of Phoreiobothrium faunas in Rhizoprionodon acutus species complex.

It has been shown that the milk shark, Rhizoprionodon acutus (Rüppell), is probably a complex of four narrowly distributed cryptic species. To confirm this hypothesis, the oioxenous species of the onchoproteocephalid genus Phoreiobothrium Linton, 1889 was recently used to recognize each shark species of this species complex so that P. nadiae Caira and Jensen, 2015, P. swaki Caira and Jensen, 2015, and P. jahki Caira and Jensen, 2015 were described respectively from Rhizoprionodon cf. acutus 1 off Senegal, R. cf. acutus 2 off northern Australia, and R. cf. acutus 3 off Borneo. Nonetheless, the Phoreiobothrium fauna of R. acutus sensu stricto extending around the Arabian Peninsula remained unknown. In the present study, P. golchini n. sp. is described from the fourth type of this shark species complex, i.e. R. acutus sensu stricto, from the Persian Gulf. Given the oioxeny of the Phoreiobothrium species and the recent phylogeny of the milk shark species complex, if the hypothesis of the allopatric cospeciation of the members of the milk shark species complex and their cestodes is considered, it seems that scolex in Phoreiobothrium can diverge more rapidly in size and morphology than strobila. Furthermore, P. rozatii n. sp. was described from one of the members of the hardnose shark species complex, i.e. Carcharhinus macloti (Müller and Henle), in the Gulf of Oman. This study provides the first data on the occurrence of the species of Phoreiobothrium in the Persian Gulf and the Gulf of Oman.