Karyotype characterization of three species of the genus Trichomycterus (Teleostei, Siluriformes) from Iguaçu river basin.

Three species belonging to the genus Trichomycterus were collected from Iguaçu river basin and analyzed from the cytogenetic point of view. Although the species studied had the same diploid number 2n = 54 chromosomes and fundamental number 108, they differed in their karyotypic formulae. C-band patterns showed presence of specific-species markers in T. davisi and T. stawiarski. Results of analysis from the nucleolus organizer region, obtained by silver nitrate staining and CMA3, showed that size heteromorphism observed in this region may be due to gene duplication. Evolution aspects of the Trichomycteridae family and the presence of B chromosome in T. davisi are discussed.