Evolução cariogenômica em peixes recifais das famílias Acanthuridae (Acanthuriformes) e Holocentridae (Holocentriformes)

Abstract

The families Acanthuridae and Holocentridae are groups of marine fish with high representation in coral reefs, where they play important ecological functions in environmental balance. Biological, phylogeographic and taxonomic aspects of these families are widely known, however, their cytogenetic aspects are incipient. In order to increase the knowledge about karyotypic evolution and possible interpopulation cytogenetic variations, four species of Acanthuridae (A. coeruleus, A. bahianus and A. chirurgus - Western Atlantic; and Acanthurus triostegus - Indian) and three Holocentridae species were analyzed. (Myripristis jacobus, Holocentrus adscensionis - West Atlantic; and Sargocentron rubrum – Indian Ocean). The analyzes used conventional cytogenetic techniques, base-specific fluorochrome staining and repetitive sequence mapping of 18S rDNA, 5S rDNA, histones H3 and H2B-H2A, microsatellites (GA)15, Tol2 transposons and Rex3 retrotransposon through fluorescent in situ hybridization. Between Acanthuridae, A. triostegus showed a karyotypic pattern considered basal for Percomorpha (2n = 48; NF = 48), while West Atlantic species exhibited a sequential karyotypic divergence associated with phylogenetic divergence. Interpopulation variation of 18S rDNA sites was identified between A. coeruleus populations of the Western Atlantic and Caribbean. The mapping of 18S rDNA, 5S rDNA, DNAhis H2B-H2A and H3 sites showed microstructural patterns in the Acanthurus genus. Holocentric species M. jacobus and S. rubrum presented 2n = 48 acrocentric chromosomes, while H. adscensionis, 2n = 50 (2m + 6sm + 16st + 26a). In this group the 18S and 5S rDNA sites constitute discriminating cytotaxonomic markers, where Rex elements and microsatellite repeats (GA)15 were co-located. Despite the wide geographical distances, no interpopulation variations were observed in M. jacobus and H. adscensionis. The results indicated a more diverse horotelic evolution in Atlantic Acanthurus species, with latest diversification, in relation to A. triostegus, belonging to the Indo-Pacific, center of origin of this group. While the presence of 2n = 48a karyotypes in Holocentrinae (Sargocentron) and Myripristinae (Myripristis) species, highlights the sharing of a conserved condition in Percomorpha and suggests an ancestral condition for the Holocentriformes. Both groups reveal phylogenetic divergences, but also the maintenance of chromosomal homeologies, and possible signs of population variation (A. coeruleus), highlighting the importance of cytogenomic analyzes correlated with biogeographic patterns in understanding karyotypic changes in marine groups.