Adaptive radiation in Antarctic notothenioid fish: Studies of genomic change at chromosomal level

The suborder Notothenioidei (Perciformes) includes about 130 species dominating the coastal Antarctic ichthyofauna. Chromosomes and karyotypes of representatives of the eight notothenioid families were studied in various Antarctic regions, allowing the Authors to describe the patterns of chromosomal diversification that accompanied the adaptive radiation of this unique group of fish. Both traditional karyotyping and the molecular cytogenetic methods were used to study chromosomal changes. As in most Perciformes, a diploid number of 48 was the most frequent value among the suborder but the various families differed greatly in their degree of interspecific karyotypic diversity. In some species, fluorescence in situ hybridisation allowed a detailed chromosome characterisation, including mapping of ribosomal genes and telomeric sequences, thus providing information on processes of karyotypic rearrangement and direction of chromosomal change. Active processes of genomic restructuring lead to intraspecific variability in several species, at different levels of chromosomal organisation. Advances in cytogenetics at the molecular level provide new perspectives for understanding how changes in genome organisation are correlated with critical events in the evolution and adaptation of Antarctic fish.