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

The suborder Notothenioidei (Perciformes) includes about 130 species domina ting the coastal Antarctic ichthyofauna. Chromosomes and karyotypes of repr esentatives of the eight notothenioid families were studied in various Anta rctic regions, allowing the Authors to describe the patterns of chromosomal diversification that accompanied the adaptive radiation of this unique gro up of fish. Both traditional karyotyping and the molecular cytogenetic meth ods were used to study chromosomal changes. As in most Perciformes, a diplo id number of 48 was the most frequent value among the suborder but the vari ous families differed greatly in their degree of interspecific karyotypic d iversity. In some species, fluorescence in situ hybridisation allowed a det ailed 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 gen omic restructuring lead tu intraspecific variability in several species, at different levels of chromosomal organisation. Advances in cytogenetics at the molecular level pro vide new perspectives for understanding how changes in genome organisation are correlated with critical events in the evolutio n and adaptation of Antarctic fish.