Redescription of Ptychobothrium belones (Dujardin, 1845) (Cestoda: Bothriocephalidea) from needlefishes (Beloniformes: Belonidae) in the Mediterranean Sea.

The bothriocephalidean tapeworm Ptychobothrium belones (Dujardin, 1845) Lönnberg, 1889 is redescribed on the basis of new materials collected from the intestine of the Mediterranean needlefish Tylosurus imperialis (Rafinesque) (Beloniformes: Belonidae) off Tunisia in the central Mediterranean Sea. This species is characterised by a laterally compressed hexagonal to fan-shaped scolex with an apical disc and two well-developed bothria, an oval ovary and numerous testes arranged in lateral and median fields. The typical diagnostic feature of P. belones is the medullary yolk follicles located between the muscle fibres of the internal longitudinal muscles (paramuscular) and the uterine duct strongly sinuous, S-shaped in mature proglottides. New molecular data (partial sequence of nuclear large subunit ribosomal RNA gene) confirmed the close relationship with specimens previously collected by Brabec et al. (2006, 2015) from the banded needlefish Strongylura leiura (Bleeker) off the Maldives, Indian Ocean, but these specimens are most likely another species. Thus, Ptychobothrium belones as previously reported represents most likely more than one species and its cosmopolitan distribution and host specificity revised by Kuchta et al. (2008b) should be revisited. The type material of P. belones was reported as collected in Mediterranean Sea off Sète, France, from Belone belone (Linnaeus); however, this host was probably misidentified, being confused with morphologically similar small specimens of T. imperialis. This study confirms that P. belones is an exclusive parasite of needlefishes (Belonidae) but at least one further species infecting S. leiura may exist.