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Genome of 'living fossil' provides insights into evolution (Interesting Science)

17/07/2015

The coelacanth is a member of an ancient group of lobe-finned fishes originally thought to have gone extinct during the Late Cretaceous period (approx. 70 million years ago), way back when Tyrannosaurus Rex walked the earth.

That is until, in 1938, it was discovered in a fishing trawler off the coast of South Africa.

In more recent years, researchers from all corners of the world, led by Chris Amemiya from the University of Washington at Seattle, have published the draft genome of the coelacanth.

This achievement allowed the researchers to show that, although coelacanth fins certainly look like they could have evolved into limbs for walking on land, lungfish are more related to tetrapods than coelacanths are. Tetrapods (literally meaning ‘four-footed’) are all the evolutionary results of the first lobe-finned fishes to crawl onto land, including amphibians, reptiles, mammals and birds.

When looking at the genes responsible for an organism’s basic body plan, the researchers were also able to highlight few differences in protein-coding regions of DNA between the coelacanth and other living tetrapods. This means that these crucial regions of DNA have remained remarkably conserved during the vertebrate transition from water to land.

Coelacanths are astonishing creatures that have barely changed in millions of years. Curiously, they are evolving significantly slower than most non-mammalian tetrapods, though the plasticity of their genome – how easily it can change in response to environmental factors – is no different to a number of other genomes of different species.

In other words, although the coelacanth genome has the potential to evolve in response to its environment, it hasn’t. It is thought this may simply be due a lack of necessity: the coelacanth has lived in a static habitat with a notable lack of predators over a long period of time, and as the saying goes, ‘if it ain’t broke, don’t fix it.’

- Emily Hardy BSc

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