Researchers at the University of Toronto have found that the last common land-dwelling ancestor of whales and dolphins adapted its vision to light in water. The results of the study were published in the journal. Proceedings of the National Academy of Sciences.
The ancestors of whales were terrestrial artiodactyls. The transition to an aquatic lifestyle required many adaptations from them, including at the molecular level. One of them is the ability to see in the absence of light. To do this, they had to replace the rhodopsin protein, which absorbs the amount of light and plays a role in stimulating the optic nerve.
Using models of evolutionary change in genes, scientists were able to reconstruct the sequence of the gene responsible for rhodopsin synthesis in the last common ancestor of whales and dolphins. By “planting” this gene into cells in the lab, they were able to obtain the rhodopsin modification that the extinct land animals had.
Judging by their chemical properties, their eyes allowed them to quickly switch between different degrees of illumination and navigate well in the aquatic environment. This confirms that the terrestrial ancestors of whales and dolphins were excellent divers, closely related to water, and their special rhodopsin later helped them transition to a purely aquatic lifestyle.