SEP 26, 2019 4:42 PM PDT

Dolphins Lost 85 Genes to Become Aquatic

WRITTEN BY: Annie Lennon

Dolphins, whales and porpoises are marine mammals; otherwise known as cetaceans. Although they live exclusively underwater nowadays, tens of millions of years ago, they looked quite different. Instead of navigating the oceans, they had legs and hooves, and walked on land. So what happened? How did they evolve into the marine animals we know today?

For some time now, researchers have been aware of the physiological adaptations cetaceans underwent to better live under water. Transitioning via semi-aquatic species such as the Pakicetus, the ancestors of modern whales and dolphins gradually lost some of their smell and taste receptors alongside their body hair. They also got better at transporting oxygen to their blood and generating body heat, while feet merged into flippers, tails into propellers and blow holes grew on their backs (Scharping: 2019). 

Despite these aesthetic observations however, biologists had little idea of the genetic journey these animals had taken to reach their aquatic state. Thus, researchers from both Germany and the US set out to delve deeper into why this happened. To do so, they compared protein-coding genes in humans with those in cetaceans and hippopotamuses, cetacean’s most closely related land animal. In the end, they found 85 genes that cetaceans lost around 50 million years ago while beginning their transition into being fully aquatic; 62 of which had never been reported before. 

Among the genes lost, the researchers found a gene that regulates saliva production, known as SLC4A9. As cetaceans live under water, they don’t need saliva to lubricate or help digest food. Furthermore, producing less saliva may have also helped their bodies better retain fresh water, beneficial when living in moisture-sapping saltwater (Hesman Saey: 2019). 

More than this, they also lost genes involved in regulating blood pressure and blood clotting. This was likely to prevent dangerous blood clots that cause strokes when quickly diving and resurfacing (Hess: 2019). Meanwhile, their loss of another gene, known as POLM, which encodes an error-prone DNA repair enzyme, likely helped streamline the function of other genes that worked better in repairing DNA (ibid.). 

According to the researchers: “More generally, our study highlights important genomic changes that occurred during the transition from land to water in the cetacean lineage and thus helps to understand the molecular determinants of their remarkable adaptations (Hess: 2019).”


Sources 

 

Scharping, Nathaniel: Discover 

Hesman, Saey: Science News 

Hess, Peter: Inverse

About the Author
  • Science writer with a keen interest in behavioral biology, consciousness medicine and technology. Her current focus is how the interplay of these fields can create meaningful interactions, products and environments.
You May Also Like
MAY 12, 2021
Health & Medicine
Researchers Discover a New Genetic Disease that Prevents Antibody Formation
MAY 12, 2021
Researchers Discover a New Genetic Disease that Prevents Antibody Formation
Doctors at the Children's Hospital of Philadelphia discovered a new genetic disease that prevents B cell development.
MAY 13, 2021
Genetics & Genomics
The Unique Caecilians of São Tomé Island
MAY 13, 2021
The Unique Caecilians of São Tomé Island
There are many islands that have unique flora and fauna, like these limbless creatures (Photo © Andrew Stanbridge) of Sã ...
JUN 23, 2021
Genetics & Genomics
Expansive RNA Atlas Includes Coding & Non-Coding Molecules
JUN 23, 2021
Expansive RNA Atlas Includes Coding & Non-Coding Molecules
We'e sequenced the human genome, even the parts that are highly repetitive, don't code for protein, and are extremely ch ...
JUN 25, 2021
Genetics & Genomics
Towards More Efficient Plant Engineering with CRISPR-Cas9 Gene Drive
JUN 25, 2021
Towards More Efficient Plant Engineering with CRISPR-Cas9 Gene Drive
Many people in the world don't have access to enough food. And while humans might find ways to adapt to a changing world ...
JUN 27, 2021
Cell & Molecular Biology
Organoids Reveal Common Mechanism Underlying Rare Disorders
JUN 27, 2021
Organoids Reveal Common Mechanism Underlying Rare Disorders
Genetic testing has shown that mutations in a gene called HUWE1 are connected to rare syndromes that cause developmental ...
JUN 27, 2021
Genetics & Genomics
How Colorful Geckos Can Teach Us About Biology
JUN 27, 2021
How Colorful Geckos Can Teach Us About Biology
A colony of Lemon Frost geckos was created by the reptile shop of Steve Sykes, which included Mr. Frosty, seen here cour ...
Loading Comments...