Hydrophis cyanocinctus. Credit: Chris Mitchell
Key points:
- Sea snakes have adapted to their colorful environment by enhancing their color vision.
- A new study shows this rare feat is due to gene duplication.
- The study suggests expanded color vision is more common than originally thought.
For sea snakes, adapting to their surroundings means embracing color. In a new study, an international team of scientists found that the species has enhanced their color vision over the years in response to living in brighter and more colorful marine environments.
“The earliest snakes lost much of their ability to see color due to their dim-light burrowing lifestyle. However, their sea snake descendants now occupy brighter and more spectrally complex marine environments. We believe that recent gene duplications have dramatically expanded the range of colors sea snakes can see,” said lead author Isaac Rossetto, researcher at the University of Adelaide.
In their study, published in Genome Biology and Evoution, Rossetto and team focused on visual opsin genes. They examined published reference genomes and gene data on Hydrophis cyanocinctus, or the annulated sea snake, a species of venomous snake found in tropical and subtropical regions of Australia and Asia.
The researchers found that annulated sea snakes possess four intact copies of the visual opsin gene SWS1. Two have ancestral ultraviolet sensitivity, while the other two have evolved a new sensitivity to the longer wavelengths that dominate today’s ocean habitats.
Many animals have lost opsins throughout their genealogical history as they’ve adapted to new habitats, but it is very rare to see opsin gains.
“Humans have a similarly expanded sensitivity to colors, while cats and dogs are partially color-blind much like those early snakes,” said Rossetto. “It’s unique and interesting that these snakes appear to be gaining and diversifying their opsins, when other land-to-sea transitioned animals have done the opposite.”
Evidence of color vision in the annulated sea snake was first published in 2020, but this new research shows it is the result of gene duplication rather than gene polymorphism. This means expanded color vision is more common among the species than originally thought.