A marine snake has developed the ability to see colors after losing it millions of years ago. This is a rare phenomenon, as only two reptiles are known to have regained this type of color vision.
In the past, snakes primarily lived in dimly lit forest habitats, where they were exposed to a limited range of colors. As a result, they evolved to lose two of their five genes for color vision, known as opsins.
Over the last 25 million years, more than 60 species of snakes have adapted to brighter and more colorful marine environments. One of these species is the venomous blue-banded sea snake (Hydrophis cyanocinctus), found in the shallow waters of tropical Australia and Asia.
Prior research had suggested that some individuals of the blue-banded sea snake had the SWS1 opsin gene, which allows for color vision. However, it was not widespread, and the presence of the gene in individuals was determined by genetic chance.
Researchers at the University of Adelaide in Australia analyzed the genomic data from five species of snakes in the Elapidae family, including the blue-banded sea snake. They found that the blue-banded sea snake has evolved to regain and duplicate the ancestral SWS1 gene, a rare occurrence among snakes.
This rediscovered ability to see color suggests that it is not merely an evolutionary accident. The blue-banded sea snake now joins a group of interesting marine snakes with color vision.
Two of the duplicated copies of the SWS1 gene in the blue-banded sea snake sense ultraviolet light, which is abundant at the surface of seas and oceans. The other two copies have evolved to sense blue light, the primary wavelength that reaches the depths. This adaptation allows the snake to effectively see colors in both its surface and deep-sea environments.
This discovery implies that the blue-banded sea snake outperforms other snake species in terms of color vision, providing an advantage in spotting prey or predators and navigating its environment. Previously, the only known case of this color-vision gene among reptiles was the water snake (Helicops angulatus).
Although this finding is exciting, Yohey Terai from SOKENDAI in Japan cautions that the presence of genes alone does not guarantee their use for color vision. Further experiments are needed to test the color vision of the sea snakes.
