Therodamas fluviatilis (Copepoda: Ergasilidae), a parasite of Paralichthys orbignyanus (Teleostei: Paralichthyidae) from Lagoa dos Patos estuary and adjacent coastline, State of Rio Grande do Sul, Brazil

Abstract

The gills of 109 specimens of the flounder Paralichthys orbignyanus from Lagoa dos Patos estuary and adjacent Rio Grande do Sul coast (Brazil) were examined in order to verify the probable presence of parasites. The high commercial value and the tolerance to abiotic factors variations exhibited by the fish P. orbignyanus point to the potentiality of its rearing, justifying the studies on associated parasitic fauna. In the gills of the flounder it was registered the presence of parasites of the Therodamas genus, and in this genus only the adult females are mesoparasitic. The parasite was studied and identified as T. fluviatilis, and its original description is the only available. This is the first record of that parasite in a marine host, although being an estuarine-dependent fish. It is also the first record in fish from the Brazilian coast, and the flounder P. orbignyanus is a new host for the parasite species. This fact justifies the description of the parasite, which was made through drawings and measures. The present description is compared with those of other species of Therodamas, and the registered differences are discussed. Until then, T. fluviatilis has being only recorded in material from Characidae collected in Argentina, suggesting that these parasites are distinct species. The fact that the fish Paralichthys orbignyanus tolerates low levels of salinity and lives together with several species of freshwater fish in the estuary justifies the registration of the occurrence of the parasite T. fluviatilis.