Extensive chromosomal homologies and evidence of karyotypic stasis in Atlantic grunts of the genus Haemulon (Perciformes)

Abstract

Fish of the genus Haemulon, known as grunts, are common in coral reefs, displaying a large trophic and economic importance. Recent evidence suggests the occurrence of sympatric speciation and hybridization during the differentiation process of some species. Chromosomal analyses based on conventional cytogenetic markers have revealed the presence of conserved karyotypes, with few identifiable rearrangements in most species. In this study, we compared the cytogenetic data of the species Haemulon aurolineatum, Haemulon plumierii, and Haemulon steindachneri, using different staining methods (C-, Ag-, and DAPI/CMA 3 banding), in situ digestion by restriction endonucleases ( AluI, EcoRI, PstI, and TaqI) and chromosomal mapping of ribosomal genes (18S and 5S) by double-FISH. All species displayed the karyotype comprising 2n = 48 acrocentric chromosomes and with accentuated chromosomal homologies, which suggest the maintenance of extensive syntenic content evolutionarily maintained with few changes. H. aurolineatum and H. plumierii, from the coast of Brazil, have subtle but identifiable cytogenetic differences in relation to populations from other parts of the Atlantic, reflecting the disruptive role of the biogeographical barriers between these regions. Karyotypic conservatism in this genus shows a karyotypic stasis, probably related to intrinsic characteristics of the karyotype itself and/or biological characteristics of this group of fish.