Species diversity of parasitic flatworms of the order Trypanorhyncha Diesing, 1863 from neotropical freshwater stingrays (Myliobatiformes: Potamotrygonidae)

Abstract

Neotropical freshwater stingrays of the family Potamotrygonidae (Chondrichthyes: Myliobatiformes) represent the only family of elasmobranchs entirely restricted to freshwater habitats of South America. Like their marine relatives, they are infected with metazoan parasites, including many species of cestodes that use elasmobranchs as definitive hosts (e.g., Tetraphyllidea, Rhinebothriidea and Trypanorhyncha). Numerous reports of cestodes infecting potamotrygonid hosts can be found in the literature (see e.g., Luchetti et al., 2008; Marques, 2000; Marques & Brooks, 2003; Marques et al., 2003a, b; Reyda, 2008; Reyda & Marques, 2011). However, almost every record addresses tetraphyllidean and rhinebothriidean infections, but rarely trypanorhynchs. Cestodes of the order Trypanorhyncha are cosmopolitan parasites, predominately found in marine habitats. In Brasil, many researchers focused on larval stages of trypanorhynchs from marine fishes, while the adult worms from the spiral valve of elasmobranchs are far less frequently reported. In contrast, only two trypanorhynch species, Paroncomegas araya (Woodland, 1934) and P. baeri (López-Neyra & Días Ungría, 1958), were reported from potamotrygonid definitive hosts in South American freshwater systems. Due to the lack of knowledge regarding this particular group of cestodes, the focus on the species diversity in potamotrygonid freshwater stingrays should be further investigated. (AU)