Species of Rhinebothrium (Tetraphyllidea: Phyllobothriidae) from freshwater stingrays in Argentina

ADRIANA MENORET; VERÓNICA A. IVANOV

Smolenice

Workshop; VI International workshop on cestode systematics and phylogeny; 2008

Academia de Ciencias de Eslovaquia

Cestodes in the genus Rhinebothrium(Tetraphyllidea, Phyllobothriidae) have been reported from marine and freshwater elasmobranchs. Among the valid species in the genus, 35 were collected from marine hosts and only 5 species are restricted to hosts confined to freshwater environments. So far, only 2 species, Rhinebothrium paratrygoni, Rhinebothrium copianullum have been recovered from potamotrygonid stingrays in the Neotropical region in South America. Recent collections were made of Rhinebothrium spp. from potamotrygonids in the Paraná Basin, allowing the evaluation of the diversity and host specificity of this genus in Argentina. During this study, specimens of Rhinebothrium were collected from 3 species of stingrays (Potamotrygon motoro, Potamotrygon falkneri, and Potamotrygonbrachyura)in Colastiné and Coronda rivers Paraná Basin. The worms were studied based on whole mounts, histological sections, and scanning electron microscopy. Morphological similarity was examined using multivariate statistical methods (cluster and principal component analysis). Based on the results, 3 species were clearly distinguished: P. falkneri Rhinebothrium sp. 2 from P. motoro, P. brachyura; and Rhinebothrium sp. 3 from P. motoro. Only one species was found in more than one host. It seems possible that host specificity in this system is higher than previously reported. The discovery of these species shows that the genus Rhinebothrium is more diverse in freshwater environments than previously estimated, and suggests that additional species of Rhinebothrium might be found in potamotrygonids with the increase of sampling effort for these hosts.