Characterization and description of a multiple sex chromosome system in Potamotrygon motoro (Chondrichthyes, Myliobatiformes) from the Paraná River, Argentina.

The Potamotrygonidae family represents the only freshwater group of specialized elasmobranchs and is composed of 4 genera: Plesiotrygon, Paratrygon, Potamotrygon, and Heliotrygon. Individuals of Potamotrygon motoro were collected from the Paraná River at Ituzaingó (Province of Corrientes) in Argentina. Mitotic preparations were obtained using direct techniques and lymphocyte cultures.

Comparative cytogenetic studies of Curimatidae (Pisces, Characiformes) from the middle Paraná River (Argentina).

Almost all species of the Curimatidae family have a stable karyotype, with a diploid number of 54 metacentric (M) and submetacentric (SM) chromosomes, and one sole nucleolus organizer pair. This family has considerable specific diversity in Argentinean fluvial basins; however, no cytogenetic data are available. Eight species from the Paraná River (Argentina): Cyphocharax voga, C.