Rhabdochona mexicana: a Mexican endemic species parasitizing a characid fish in Argentina

ROSSIN, M.A.; TIMI, J.T.

Viña del Mar

Simposio; VIII International Symposium on Fish Parasites; 2011

Universidad de Antofagasta, Chile

The genus Rhabdochona (Rhabdochonidae, Thelazioidea) includes 92 valid species distributed in all zoogeographical regions. Of the 24 nominal species known in the Americas, 21 have been found exclusively in North America and are primarily parasites of the cypriniformes; whereas only 3 species belong to the South American helminth fauna, namely R. acuminata, R. fabianae and R. uruyeni, all parasites of characiformes. The Cyprinidae seems to be the main host family in all biogeographical zones where species of Rhabdochona have been found, except for South America where there are no cyprinids. Moravec (2010) suggest that representatives of Rhabdochona migrated with characiforms from North America through the Panama Isthmus, since Pleiocene. Oligosarcus jenynsii (Characidae) is a widely distributed neotropical freshwater fish and it is one of the dominant pelagic fish in all lagoons of Pampasic region. During a parasitological survey carried out during 2008-2010, 62 specimens of Oligosarcus jenynsii were captured at Nahuel Ruca lagoon (Buenos Aires province, Argentina). Nematodes referable to Rhabdochona were collected and examined under light and SEM microscopy. Morphology and morphometry of these nematodes fully agreed whit those of R. mexicana, known as an endemic Mexican species, parasite of Astyanax mexicanus (Characidae).Therefore, both the range of hosts and geographic distribution of this species are broadened. Zoogeographical implications of this finding are also considered.Rhabdochona (Rhabdochonidae, Thelazioidea) includes 92 valid species distributed in all zoogeographical regions. Of the 24 nominal species known in the Americas, 21 have been found exclusively in North America and are primarily parasites of the cypriniformes; whereas only 3 species belong to the South American helminth fauna, namely R. acuminata, R. fabianae and R. uruyeni, all parasites of characiformes. The Cyprinidae seems to be the main host family in all biogeographical zones where species of Rhabdochona have been found, except for South America where there are no cyprinids. Moravec (2010) suggest that representatives of Rhabdochona migrated with characiforms from North America through the Panama Isthmus, since Pleiocene. Oligosarcus jenynsii (Characidae) is a widely distributed neotropical freshwater fish and it is one of the dominant pelagic fish in all lagoons of Pampasic region. During a parasitological survey carried out during 2008-2010, 62 specimens of Oligosarcus jenynsii were captured at Nahuel Ruca lagoon (Buenos Aires province, Argentina). Nematodes referable to Rhabdochona were collected and examined under light and SEM microscopy. Morphology and morphometry of these nematodes fully agreed whit those of R. mexicana, known as an endemic Mexican species, parasite of Astyanax mexicanus (Characidae).Therefore, both the range of hosts and geographic distribution of this species are broadened. Zoogeographical implications of this finding are also considered.