Proleptus acutus (Nematoda: Physalopteridae), a parasite from an Argentinian skate, Sympterygia bonapartei (Pisces: Rajidae).

Examination of the stomach and spiral valve contents of 41 Sympterygia bonapartei Müller and Henle, 1841 (Rajiformes: Rajidae) from the Bahía Blanca estuary (38 degrees 42'S, 62 degrees 28'W), revealed the presence of the nematode Proleptus acutus Dujardin, 1845. The prevalence was 34.1% and the mean intensity was 5.75. Sympterygia bonapartei is a new host and is endemic to southern Brazil, Uruguay, and Argentina. The occurrence of P. acutus constitutes the first finding in Argentinian waters.