Chromosome change and the evolution in the Antarctic fish suborder Notothenioidei

The majority of species of the Antarctic coastal fish fauna is represented today by the perciform suborder Notothenioidei. The separation of basal lin eages of notothenioids has been estimated to have occurred between 23 and 2 2 million years ago (m.y.a.), while a major diversification probably occurr ed 16-10 m.y.a. Cytogenetic approaches aim to study the genomic change that , at the cell level, accompanied the radiation of this group. The informati on available for 66 of 120-130 species makes possible the description of th e main patterns of chromosome diversification within the suborder. Within s ome families (Channichthyidae, Artedidraconidae) the range of the chromosom al variability seems to be minimal whilst the high karyotypic diversity of Nototheniidae and Bathydraconidae is consistent with morphological and mole cular data suggesting the paraphyletic nature of these two taxa. Molecular cytogenetics allows detailed chromosome characterization, including mapping of ribosomal genes and of telomeric sequences, thus providing information on processes of karyotypic rearrangement and direction of chromosomal chang e. Active process of genomic restructuring leads to intraspecific variabili ty in several species, at different levels of chromosomal organization. The growing amount of information make it possible to use notothenioids as a m odel for testing hypotheses of evolutionary change in marine organisms, inc luding chromosomal diversification.