A groundbreaking research published in Genome Biology and Evolution, by Oxford University Press, reveals a fascinating adaptation in the annulated sea snake, a venomous species found in Australian and Asian ocean waters. The study suggests that this snake has regained the ability to perceive a wider range of colors, which its ancestors had lost due to environmental changes.
Color vision in animals is primarily regulated by genes called visual opsins. While loss of opsins has been observed in the evolution of tetrapods (including amphibians, reptiles, and mammals), the emergence of new opsin genes is exceedingly rare. Until now, the only reptilian species known to have evolved new opsin genes were those in the Helicops genus, a snake group native to South America.
This research utilized published reference genomes to investigate visual opsin genes across five different elapid snake species. Elapids, which encompass cobras, mambas, and the annulated sea snake, offer a valuable opportunity to study the molecular evolution of vision genes.
In ancient times, early snakes lost two visual opsin genes during their period of burrowing in dimly lit environments, leaving them with a limited color perception range. However, their descendants now inhabit brighter environments. Remarkably, two elapid lineages have even transitioned from terrestrial to marine habitats within the past 25 million years.
The researchers discovered 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 the longer wavelengths prevalent in ocean habitats.
It is hypothesized that this enhanced color sensitivity allows the sea snakes to better discern predators, prey, and potential mates against the colorful backdrop of the marine environment. This evolutionary process starkly contrasts with that observed in mammals such as bats, dolphins, and whales during ecological transitions, as they experienced further opsin losses while adapting to dim-light and aquatic conditions.
“The earliest snakes lost much of their color vision due to their lifestyle of burrowing in dimly lit environments,” explained Isaac Rossetto, the lead author of the paper. “However, their sea snake descendants now inhabit brighter and more visually complex marine environments. Recent gene duplications have significantly expanded the range of colors that sea snakes can perceive. Comparatively, humans also possess an expanded sensitivity to colors, while cats and dogs, like their early snake counterparts, are partially color-blind.”
More information:
Isaac H Rossetto et al, Functional Duplication of the Short-Wavelength-Sensitive Opsin in Sea Snakes: Evidence for Reexpanded Color Sensitivity Following Ancestral Regression, Genome Biology and Evolution (2023). DOI: 10.1093/gbe/evad107
Citation:
Sea snakes may have evolved to see colors again (2023, July 13)
retrieved 13 July 2023
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