Antarctic notothenioid fishes as subjects for research in evolutionary biology

Antarctica is a continental island and the waters of its shelf and upper sl ope are an insular evolutionary site. The shelf waters resemble a closed ba sin in the Southern Ocean, separated from other continents by distance, cur rent patterns and subzero temperatures. The benthic fish fauna of the shelf and upper slope of the Antarctic Region includes 213 species with higher t axonomic diversity confined to 18 families. Ninety-sis notothenioids, 67 li parids and 23 zoarcids comprise 45%, 32% and 11% of the fauna, a combined t otal of 88%. In high latitude (71-78 degrees S) shelf areas notothenioids d ominate abundance and biomass at levels of 90-95%. Notothenioids are also m orphologically and ecologically diverse. Although they lack a swim bladder, the hallmark of the notothenioid radiation has been repeated diversificati on into water column habitats. There are pelagic, semipelagic, cryopelagic and epibenthic species. Notothenioids exhibit the disproportionate speciosi ty and high endemism characteristic of fish species flock. Antifreeze glyco peptides originating from a transformed trypsinogen gene are a key innovati on. It is not known when the modern Antarctic shelf fauna assumed its curre nt taxonomic composition. A late Eocene fossil fauna was taxonomically dive rse and cosmopolitan. There was a subsequent faunal replacement with little carryover of families into the modern fauna. Basal notothenioid clades pro bably diverged in Gondwanan shelf locations during the early Tertiary. Date s inferred from molecular sequences suggest that phyletically derived Antar ctic clades arose 15-5 m.y.a.