Sea Snakes Regain Technicolor Vision: Ancestral Loss Reversed

by Mateo Gonzalez
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evolutionary vision adaptation

Sea snakes, specifically the annulated sea snake species, have undergone a fascinating transformation by regaining their ability to perceive a broader range of colors. This remarkable reversal contrasts with their ancestors, which had lost their color vision due to adaptations to low-light environments. The evolution of the annulated sea snake’s vision includes the presence of four copies of the opsin gene SWS1, which grants sensitivity to longer wavelengths prevalent in their ocean habitats. This expanded vision plays a vital role in enabling these sea snakes to better discern predators, prey, and potential mates.

According to a recent study published in Genome Biology and Evolution by Oxford University Press, the annulated sea snake, a venomous snake species native to the waters of Australia and Asia, has developed an extended color perception.

The research, conducted by examining visual opsin genes across five distinct species of elapid snakes, sheds light on the molecular evolution of vision genes within the elapid family, which encompasses cobras, mambas, and the annulated sea snake. Early snakes had experienced the loss of two visual opsin genes during their phase of burrowing in dim-light conditions, resulting in a severely limited color range. However, some of their descendants have now transitioned to brighter environments, with two elapid lineages even adapting to marine habitats within the past 25 million years.

The study’s findings reveal that the annulated sea snake possesses four intact copies of the opsin gene SWS1. While two of these genes retain the ancestral ultraviolet sensitivity, the other two have developed a new sensitivity to longer wavelengths, prevalent in the marine habitats they inhabit. The researchers speculate that this heightened sensitivity enhances the sea snakes’ ability to discriminate between colors, aiding them in distinguishing predators, prey, and potential mates against the vibrant marine backgrounds. This evolutionary pattern starkly differs from that observed in mammals like bats, dolphins, and whales, which experienced further opsin losses while adapting to dim-light and aquatic environments.

Lead author Isaac Rossetto explains, “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 visually complex marine environments. We believe that recent gene duplications have significantly expanded the range of colors that sea snakes can perceive. As a point of reference, humans also possess a similarly broadened sensitivity to colors, while cats and dogs are partially color-blind, much like those early snakes.”

To learn more about this groundbreaking discovery, refer to “The Remarkable Vision Evolution of Sea Snakes.”

Reference: “Functional Duplication of the Short-Wavelength-Sensitive Opsin in Sea Snakes: Evidence for Reexpanded Color Sensitivity Following Ancestral Regression” by Isaac H Rossetto, Kate L Sanders, Bruno F Simões, Nguyen Van Cao, and Alastair J Ludington, 12 July 2023, Genome Biology and Evolution.
DOI: 10.1093/gbe/evad107

Funding: Australian Research Council Discovery Project

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Frequently Asked Questions (FAQs) about evolutionary vision adaptation

Q: What is the significance of the annulated sea snake’s evolution in perceiving an extended color range?

A: The annulated sea snake’s ability to perceive an extended color range is significant because it represents a reversal of ancestral vision loss. While their ancestors had lost color vision due to adaptations to low-light environments, the annulated sea snake has evolved to see a wider range of colors. This evolutionary adaptation includes having four intact copies of the opsin gene SWS1, which provides sensitivity to longer wavelengths found in their ocean habitats. This expanded vision enables sea snakes to better distinguish predators, prey, and potential mates against colorful marine backgrounds.

Q: How was the study conducted to examine visual opsin genes in sea snakes?

A: The study used published reference genomes to analyze visual opsin genes across five ecologically distinct species of elapid snakes. Elapids are a family of snakes that include cobras, mambas, and the annulated sea snake. By investigating the molecular evolution of vision genes in this family, researchers gained insights into the history and adaptations of sea snakes’ visual capabilities. The study compared the presence and characteristics of opsin genes in different snake lineages, shedding light on the specific changes that occurred in the annulated sea snake’s visual system.

Q: What role do opsin genes play in color vision?

A: Opsin genes are crucial for determining color vision in animals. These genes encode proteins called opsins, which are light-sensitive pigments found in photoreceptor cells of the eyes. Different types of opsins respond to different wavelengths of light, allowing organisms to perceive a range of colors. In the case of the annulated sea snake, the presence of four copies of the opsin gene SWS1 indicates an expanded sensitivity to both ultraviolet and longer wavelengths, enhancing their ability to perceive a broader spectrum of colors.

Q: How does the evolution of the annulated sea snake’s color vision differ from that of mammals?

A: The evolution of color vision in the annulated sea snake differs from that of mammals like bats, dolphins, and whales. While sea snakes regained color vision by evolving new opsin genes, these mammals experienced further opsin losses as they adapted to dim-light and aquatic environments. The annulated sea snake’s ancestors lost their ability to see color due to their dim-light burrowing lifestyle. However, the sea snake descendants now occupy brighter and visually complex marine environments, leading to recent gene duplications and the expansion of color sensitivity. This contrast highlights the diverse evolutionary paths taken by different species in response to their respective environments.

Q: What are the potential benefits of the annulated sea snake’s expanded color vision?

A: The expanded color vision of the annulated sea snake likely provides several benefits. It helps them distinguish predators, allowing them to better evade dangerous encounters. Additionally, the ability to perceive a broader range of colors assists in identifying suitable prey and potential mates amidst the vibrant marine backgrounds. By enhancing their color discrimination, the expanded color vision of sea snakes improves their overall survival and reproductive success in their ocean habitats.

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