Comparative cytogenetics and heterochromatic patterns in two species of the genus Acanthostracion (Ostraciidae: Tetraodontiformes)

Chromosomal Evolution and Cytotaxonomy in Wrasses (Perciformes; Labridae)

The wrasses (family Labridae) represent a suitable model to understand chromosomal evolution and to test the efficacy of cytotaxonomy since they display a remarkable karyotypic variation, rarely reported in marine Perciformes, as well as a high number of species and complex systematics. Therefore, we provided new chromosomal data in 5 labrids from South Atlantic (Doratonotus megalepis, Halichoeres dimidiatus, Halichoeres penrosei, Thalassoma noronhanum, and Xyrichtys novacula) and carried out a detailed comparative analysis of karyotypic data in Labridae using multivariate approaches. Basal diploid values (2n = 48) were observed in most of species studied in the present work but D. megalepis (2n = 46), along with distinct karyotype formulae. Single 18S rDNA sites interspersed with GC-rich heterochromatin were also commonly reported except for both Halichoeres species (2 18S rDNA-bearing pairs), following a species-specific pattern. These data show the high rates of chromosomal evolution in wrasses, ranging from microstructural rearrangements to centric fusions. A revision of chromosomal data in Labridae based on multivariate analysis of 74 taxa allowed inferring karyoevolutionary trends within tribes and genera of wrasses. The dendrogram obtained was in agreement with recent systematic hypotheses. In spite of the independent occurrence of some chromosomal rearrangements, karyoevolutionary trends could be identified within tribes of Labridae. Moreover, the karyotypic features are also suitable as cytotaxonomic markers of wrasses.