Sea snakes evolve to see an extended palette of colors

A recent publication in Genome Biology and Evolution, which was published by Oxford University Press, has made an intriguing discovery regarding the annulated sea snake. This venomous snake species, found in the waters surrounding Australia and Asia, seems to have evolved an extended range of color vision after its ancestors lost that ability due to changing environments.

The ability to perceive colors in animals is primarily determined by visual opsins, a group of genes responsible for color vision. While the loss of opsin genes has occurred multiple times during the evolution of tetrapods (including amphibians, reptiles, and mammals), the emergence of new opsin genes is exceedingly rare. Prior to this study, the only known instance of new opsin gene evolution within reptiles was observed in certain species of Helicops, a snake genus from South America.

To investigate the molecular evolution of vision genes, researchers examined the visual opsin genes in five ecologically distinct species of elapid snakes using publicly available reference genomes. Elapids, which include cobras, mambas, and the annulated sea snake, offer an excellent opportunity to study the history of vision gene evolution.

In the early stages, snakes lost two visual opsin genes during their phase of burrowing in dim-light environments, limiting their ability to perceive a wide range of colors. However, some of their descendants have since transitioned to brighter habitats, with two elapid lineages even moving from terrestrial to marine environments over the past 25 million years.

The study revealed that the annulated sea snake possesses four intact copies of the opsin gene SWS1. Two of these genes retain the ancestral ultraviolet sensitivity, while the other two have developed a new sensitivity to longer wavelengths, which are more prevalent in ocean habitats.

The researchers hypothesize that this expanded color sensitivity may enhance the sea snakes’ ability to distinguish predators, prey, and potential mates against the vibrant marine backgrounds. This evolutionary pattern stands in stark contrast to the opsin evolution observed in mammals like bats, dolphins, and whales during ecological transitions, where further opsin losses occurred as they adapted to dim-light and aquatic environments.

“The early snakes lost much of their color vision due to their burrowing lifestyle in dim-light conditions,” explained the lead author of the paper, Isaac Rossetto. “However, their sea snake descendants now inhabit brighter and visually diverse marine environments. We believe that recent gene duplications have significantly broadened the range of colors that sea snakes can perceive. To draw a comparison, humans have a similarly expanded color sensitivity, while animals like cats and dogs are partially color-blind, akin to those early snakes.”

Source: Oxford University Press

Leave a Comment