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Antarctic icefish genome reveals antifreeze genes, but no red-blood cells

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Scientists have found the antifreeze genes that allow Antarctic blackfin icefish to survive in subzero temperatures of the Southern Ocean. The icefish is known to be the only 'white-blooded' vertebrate, meaning it lacks red blood cells and haemoglobin genes, instead relying on a large heart and enhanced blood-vessels to carry oxygen around its body. The research also revealed a lack of genes that help regulate circadian rhythms - the fish's body clock - which is thought to be a response to the irregular day/night cycle in the Antarctic.

Journal/conference: Nature Ecology & Evolution

Link to research (DOI): 10.1038/s41559-019-0812-7

Organisation/s: Korea Polar Research Institute, Korea

Media release

Antarctic blackfin icefish genome reveals cool adaptions

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.

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