Comparação Cariotípica de Hoplias Malabaricus (bloch, 1794) (Characiformes, Erythrinidae) da Amazônia Central

Abstract

Cytogenetic studies in Hoplias malabaricus reveal the occurrence of seven karyomorphs (A to G), which are distinguishable on the diploid number, shape and size of the chromosomes as well as about the chromosomal sex determination system. However, different evolutionary units within the karyomorphs of H. malabaricus have been described, and have been assigned to different types of Amazonian waters. Thus, the present study intended to check if there is variation in cytogenomics trahiras near Manaus, AM, and this may have some association with local adaptive processes of the species under different conditions, by classical cytogenetic analysis and physical mapping of the chromosome elements repetitive. We analyzed 41 individuals collected in the Reserve Adolpho Ducke (Barro Branco River and Ipiranga River), Catalão Lake and Marchantaria Island. In the analyzes were used classical cytogenetic markers (conventional staining, C-banding and NOR) and molecular (Fluorescence in situ hybridization with probes rDNA18S, rDNA 5S, retroelement Rex 3 and telomeric sequences). Individuals of Reserve Adolpho Ducke presented 2n = 42 chromosomes, whose chromosomal macrostructure would be considered karyomorph A. Already, individuals of Catalão Lake and Marchantaria Island presented 2n = 40 chromosomes, which would be considered karyomorph C. The constitutive heterochromatin was localeted in all individuals as blocks in the centromeric and surrounding region, as well as some bitelomerics and interstitial markings. The number of chromosomes bearing nucleolar organizer regions - NOR, rDNA 5S and rDNA 18S varied between locations. The retroelement Rex 3 showed a compartmentalized distribution terminal regions of most chromosomes, as well as centromeric regions, with subtle differences among populations. FISH with telomere probe detected these regions only the end portion of chromosomes for all individuals. Thus, the data show that chromosomal macrostructure (karyomorphs A-G) is insufficient for the delimitation of evolutionary units within the complex H. malabaricus and differences in genome organization can be mainly caused by the sedentary habits of these fish, which favors the fixation of chromosomal rearrangements, and not necessarily to different types of water where they live.