Ancient climate change events ~22 million years ago led to the freezing of the Southern Ocean and the local extinction of most fish populations surrounding Antarctica. One clade of fishes, the Antarctic notothenioids, were able to adapt to the increasingly icy conditions and ultimately diversified from a single common ancestor to ~120 species today. These 120 species are so successful that this family represents around 90% of fish biomass off the Antarctic continental shelf!
As a classic example of adaptive radiation in a marine environment, notothenioids are models for understanding adaptive radiations, physiological and biochemical adaptations to extreme environments, and adaptation to climate change. With a surge in genomic and transcriptomic resources for this clade, the past decade has revealed substantial insight into molecular mechanisms of notothenioid adaptation.
In this paper we review some of the insights gained from notothenioid biology in the omics era. We discuss how the notothenioid adaptive radiation is characterized by frequent chromosomal fusions, large-scale TE mobilization, and gene family expansions and contractions that are functionally associated with the physiological stresses of life at subzero temperatures. Unstable karyotypes and dramatic changes to mutation rate in notothenioids distinguish this clade from genetic trends observed in other fish radiations. As observed in other fish species flocks, gene flow may also play an important role in the genetic history of the notothenioids. Future research on the genetic architecture and developmental mechanisms of key traits in notothenioids will help to synthesize the principles and mechanisms of adaptive radiation.
Check it out the review article here: Adaptations and Diversity of Antarctic Fishes: A Genomic Perspective