Description of a new genus of Escherbothriidae (Cestoda: Rhinebothriidea) in species of Sympterygia (Rajiformes: Arhynchobatidae) from South America based on morphological and molecular evidence, with an amended diagnosis of the family

Ivanovcestus yakiae gen. et sp. nov. was collected from specimens of the batoid Sympterygia bonapartii from waters off Río Negro and Buenos Aires Provinces, in the Argentine Sea. Ivanovcestus gen. nov. is assigned to the Rhinebothriidea for their possession of facially loculated bothridia borne on stalks and a cirrus covered by spinitriches. The new genus is unique in the arrangement of loculi and septa on the distal bothridial surface. The molecular analysis based on 18S and 28S rDNA of two specimens of the new species identified Ivanovcestus gen. nov. as a member of the family Escherbothriidae, with our study representing the first record of this family in the Argentine Sea. The proposed new genus requires a new amended diagnosis for the Escherbothriidae, to include a new pattern of loculi and septa for the distal bothridial surface, as well as a new host. In addition, the present study proposes to transfer two species of Rhinebothrium, originally described parasitizing the skate Sympterygia lima in the Chilean Sea (i.e., Rhinebothrium chilensis and Rhinebothrium leiblei), to Ivanovcestus gen. nov. Examination of the original descriptions and type material revealed several morphological characters that justify the relocation of both species to the new genus.