Heterochromatin characterization of four fish species of the family Loricariidae (Siluriformes).

The karyotypic structures and the composition and distribution of the heterochromatin in the karyotypes of four catfish species belonging to four Loricariidae subfamilies were analysed, namely: Neoplecostomus microps (Neoplecostominae) with 2n=54 chromosomes, Harttia loricariformis (Loricariinae) with 2n=56 chromosomes, Hypostomus affinis (Hypostominae) with 2n=66 chromosomes and Upsilodus sp. (Upsilodinae) with 2n=96 chromosomes. The amount and composition of heterochromatin was quite unequal among the studied species, being copious and mainly GC-rich in Upsilodus sp. and scarce and balanced in H. loricariformis. All of the H. affinis heterochromatin is GC-rich and related with nucleolar organizing regions. N. microps show low quantity of interstitial and GC-rich heterochromatin, one of them being related with NORs. Trends in the macrokaryotypic diversification as well as in the distribution pattern of the heterochromatin are discussed.