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Icefish lose their genes

04 December 2007

Antarctic icefish have lost two vital genes in their bid to survive the icy depths, according to a new study by a scientist at the Natural History Museum.

The group of almost transparent, perch-like fishes are already known to use peculiar tricks that help them survive extreme cold such as having a natural antifreeze substance in their blood.

Missing genes
November cover of the Journal of Molecular Evolution

November cover of the Journal of Molecular Evolution

The genetic information, or genomes, of mitochondria contain a fixed number of 37 genes. Mitochodria are the cell organelles responsible for respiratory functions of most animals. However, in the Antarctic fishes the ND6 and tRNA-Glu genes are missing.

'This is a striking example of how unique these Antarctic fishes are,' says Lukas Ruber, fish expert at the Natural History Museum.

'They live at subzero temperatures and such a tough environment seems to demand extreme measures.'

'It's not clear how they can cope without this essential function. It's possible that losing these two genes gives them an advantage, or that other genes compensate for the loss.'

Comparing DNA

Icefish are part of a large group of fishes known as Notothenioidei. Most of which are found in the Antarctic.

The research team compared the complete mitochondrial genome and other relevant DNA regions from one Antarctic icefish, Chionodraco rastrospinosus with those of other fish species, including a notothenioid fish that lives in sub-Antarctic waters, the Patagonian blennie.

Unknown DNA

The comparison showed that Antarctic icefish have lost the ND6 and tRNA-Glu genes and have a much shorter DNA sequence instead of these two genes and this is unlike any other known DNA fragment.

The research involved an international team of experts from the University of Cambridge, the National Natural Sciences Museum in Madrid, and the University of Padua in Italy.

The study is published in the November issue of the Journal of Molecular Evolution , where it features on the front cover.

You can see an icefish specimen on display in the Museum's exhibition Ice Station Antarctica

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