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

摘要

The family Loricariidae gathers some 600 species distributed throughout 70 genera, probably being one of the most taxonomically complex families among the Siluriformes (Isbrücker 1980). Schaefer (1987) considers six Loricariidae subfamilies (Lithogeninae, Neoplecostominae, Hypoptopomatinae, Loricariinae, Ancistrinae and Hypostominae), all constituting a monophyletic group. However, Armbruster (1997) proposed two new subfamilies, Hemipsilichthinae and Upsilodinae, the latter considered by the author as the most basal among the loricariids, with a single monotypic genus, Upsilodus victori.Cytogenetic studies are still scarce in face of the number of Loricariidae species (Alves 2000; Artoni and Bertollo 2001), being inexistent in the subfamily Lithogeninae. Kavalco (2003) estimates that only around 70 Loricariidae species have already been submitted to any sort of cytogenetic study. Its great karyotypic diversity is represented in the amplitude of variation of the diploid numbers, which range from 2n=36 in Rineloricaria latirostris (Giuliano-Caetano 1998) to 2n=96 in Upsilous sp. (Kavalco 2003). Besides this, a large structural variability in the karyotypes is also observed, as is the case of Rineloricaria latirostris (Giuliano-Caetano 1998). Heterochromatin data in this group is scarce but indicates a great diversity in amount and constitution (Artoni and Bertollo 2001).The distribution and composition of the heterochromatin in the karyotypes of 4 Loricariidae species from the Paraíba do Sul river basin, one of the most expressive and important rivers of the east Brazilian drainage system, are presented in this work. The data are discussed considering the karyotypic evolution of the group.