A high-quality genome of the Antarctic blackfin icefish is reported in a paper published online this week in Nature Ecology & Evolution. This genome reveals genetic adaptations that enable the icefish to survive in the Southern Ocean, which is cooled to subzero temperatures.
Antarctic icefish developed unique physiological adaptations to the extreme polar marine environment in which they live. They are the only vertebrates that are ‘white-blooded’, meaning that they lack functional red blood cells and haemoglobin genes. To compensate for this, icefish evolved enormous hearts and enhanced vascular systems.
Hyun Park, Manfred Schartl and colleagues sequenced the genome of an Antarctic blackfin icefish, Chaenocephalusaceratus. The authors found that in Antarctic blackfin icefish, as compared with other bony fish, such as sticklebacks, there is an expansion of antifreeze glycoprotein genes and egg coat proteins, which lower the melting point of ice and surround embryos to help them survive in the cold Antarctic waters. C. aceratusis is sensitive to cell damage caused by chemically reactive molecules containing oxygen. The authors also identified an expansion of gene families associated with reactive oxygen species homeostasis in the genome.
The authors conclude that the availability of this icefish genome may advance our understanding of adaptation to extreme Antarctic environments.