Lecanicephalidean (Cestoda) fauna of the giant freshwater whipray, Himantura polylepis (Myliobatiformes: Dasyatidae), from Malaysian and Indonesian Borneo.

Abstract

Eight species of dasyatid stingrays (Myliobatiformes) are characterized as freshwater obligate, including the giant freshwater whipray (Himantura polylepis), comprising at least three separate incursions into freshwater habitats. However, a tolerance of estuarine environments has been suggested for H. polylepis. Eight individuals of this species were collected between 2003 and 2009 at two sites in Borneo [six from the Kinabatangan River (Malaysia) and two from Tarakan (Indonesia)]; these host specimens were examined for lecanicephalidean cestodes. Collectively, these hosts were parasitized by eight species of lecanicephalidean tapeworms: three new species of Tetragonocephalum, three new species of Polypocephalus, and one species each of two as of yet undescribed genera. This brings the total number of reported cestodes from H. polylepis to 18 species in nine genera of four orders. Of the nine total genera parasitizing H. polylepis, one is unique while seven are collectively also found parasitizing marine and euryhaline dasyatid hosts. In contrast, the South American freshwater potamotrygonids are parasitized by a total of seven genera; three of these are unique to potamotrygonids while four genera also parasitize marine stingrays. The similarity of the cestode assemblage of the giant freshwater whipray to that of its marine and euryhaline relatives might be one of several lines of evidence to support the notion that this stingray may not be restricted to freshwater.