Initial Steps of XY Sex Chromosome Differentiation in the Armored Catfish (Siluriformes: Loricariidae) Revealed by Heterochromatin Accumulation.

In fish species, heterochromatinization is one process that could trigger sex chromosome differentiation. The present article describes a nascent XX/XY sex chromosome system evidenced by heterochromatin accumulation and microsatellite (GATA) in from two populations of the Paraná River basin. The specimens of from the Campo and Bossi Rivers share the same karyotype.