Heteronchocotyle gymnurae sp n. (Monogenea : Hexabothriidae), a gill parasite of Gymnura altavela (Elasmobranchii : Gymnuridae) from the Mediterranean Sea

Heteronchocotyle gymnurae sp. n. is described from the gills of the spiny b utterfly ray Gymnura altavela in the Gulf of Gabes, Tunisia. The new specie s is compared with the 2 species of Heteronchocotyle already known and with other hexabothriids possessing an asymmetrical haptor. The diagnosis of th e genus Heteronchocotyle Boeger and Kritsky, 1989, is emended by adding the course of the vagina, which opens into the transverse vitelloducts near th e median plane, the unarmed cirrus, which is not dilated distally, and the presence of a prostatic gland. This report is the first record of specimens of the genus Heteronchocotyle from Myliobatiformes.