RHABDOCHONA MEXICANA: A MEXICAN ENDEMIC SPECIES PARASITIZING A CHARACID FISH IN ARGENTINA.

ROSSIN, M. ALEJANDRA; TIMI JUAN TOMÁS

Viña del Mar

Congreso; VIII International Symposium of fish parasites; 2011

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