Walking Fish Offers Insight Into Ancient Evolutionary Transition

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Ever wondered what might have happened when the first fish “crawled” out of water? It started a long evolutionary trek, giving rise to today’s tetrapods: reptiles, amphibians, birds and mammals. But how did the fish learn to walk? Researchers at McGill University in Ottawa have put forward a new view of evolution. They used a modern-day walking fish to understand the ancient transition.

The first fish walked on land about 400 million years ago

According to a study published in the journal Nature, scientists proved that certain fish can adapt to living outside water. In fact, they develop an efficient walking mechanism. Led by Dr Hans Larsson, scientists carried out their experiment on an African fish called Polypterus. It has lungs and can breathe air. Polypterus can move on land to reach the water. More important, it looks like the ancient fish that evolved into tetrapods. All these factors made it a good subject for testing.

Researchers estimate that the first fish survived out of water about 400 million years ago. McGill University scientists examined the developmental changes associated with the transition from water to land. They raised juvenile Polypterus on land for about a year, and monitored how the ‘terrestrialized’ fish moved differently.

The land-raised fish showed many anatomical and behavioral changes

The fish showed significant behavioral and anatomical changes. Their fins came closer to their bodies. Their pectoral skeleton became stronger and more elongated, possibly to support during walking. They walked without slipping, and would lift their heads higher. Dr Larsson said many of the anatomical changes resemble the fossil record. So, researchers hypothesized that the behavioral changes in Polypterus reflect what might have happened when the ancient fish first walked with their fins on land.

As part of the experiment, scientists had also raised another group of Polypterus in water. They found that the land-raised fish had evolved into far more efficient waters than their aquatic counterparts. Check out this video to see how Polypterus walks.

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