Gene losses helped dolphins transition to life underwater

Gene losses helped dolphins transition to life underwater. Fifty million years ago, the ancestors of modern whales, dolphins, and porpoises underwent a drastic change of scenery. Once at home on land and in the water, cetaceans decided to forgo their landlubber ways and opt for a full time underwater existence. 

Now, a team of researchers has discovered which genomic changes and adaptations helped make this transition possible. 

There is a reason that whales are a close evolutionary cousin of hippos, it’s because cetaceans split off from the ancestors of modern hippopotamuses during the Early Eocene Period. 

During the switch from land to sea, 85 genes in cetaceans became inactivated or turned off. Not all these gene losses specifically aided in the transition to an aquatic habitat, but some mutations equipped the animals with new abilities like deep-sea diving and sleeping underwater. 

The researchers went hunting for gene-inactivating mutations that popped up as cetaceans started living underwater and analyzed 19,769 genes from 62 mammal species. 

One of the inactivated genes identified was involved in saliva, something no longer necessary with an aquatic diet. Two of the lost genes helped with blood clotting, which could have hindered deep dives. 

Not surprisingly, cetaceans also lost genes that were linked to lung use and allowed the lungs to collapse while diving. This helped with reducing buoyancy and adjusting the pressure changes as the animals surfaced. 

Ancient whale ancestors also adapted different sleeping patterns after losing the ability to synthesize melatonin. 

A study detailing these genomic changes, published in the journal Science Advances, provides insight into how ancient cetaceans evolved. 

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By Kay Vandette, Earth.com Staff Writer 

Image Credit: Shutterstock/Andrea Izzotti