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Australian sea snakes of the Aipysurus family spend most of their lives at sea. They grow quite long and yet maintain their agility, which helps them to hunt and to avoid the predators. However, their paddle-shaped tails are quite vulnerable just because of how far away they are from their heads. Now a study led by the University of Adelaide showed that Australian sea snakes can actually “see” with their tails, which helps protecting them.
Aipysurus laevis – one of the rare snakes that is able to sense light falling on its tail. Image credit: Sylke Rohrlach via Wikimedia (CC BY-SA 2.0)
These paddle-shaped tails are absolutely crucial for the survival of the snake. They help snakes move around, hunt and avoid the predators. However, when snakes stop, which they do several times per day, these tails become targets for various predators, such as sharks. Injured tails would make movement very difficult, which would disable the snake and possible endanger it. Scientists now found that the tails of the olive sea snakes (Aipysurus laevis) and other Aipysurus species are able to sense light, which warns the snake that it should tuck its tail in the shelter.
No other reptile from more than 10,000 species is known to respond to light on the skin in this way. This is also why scientists are so interested – this could provide some interesting insights into the evolution and genetics of this rare light sense. Scientists tested 8 species for this light-sensing ability, but they found that only three had it. Scientists don’t even know why only a few of Aipysurus species are able to sense the light with their tails. Researchers performed RNA sequencing and found a gene for a light-sensitive protein called melanopsin. Melanopsin converts light into information in the nervous system and it is not even that rare – human have it as well.
There is probably nothing common between us and the olive snakes, but we both have melanopsin. Humans, like many other animals, use this protein to regulate their sleep cycles. Meanwhile frogs use it to change their skin colour as a camouflage. Jenna Crowe-Riddell, lead author of the study, said: “We’ve confirmed the ability of olive sea snakes to sense light in their tails and found the same ability in two other species. We’ve identified a shortlist of genes that are likely to be involved in detecting light. But further study will be needed to target these genes before we can really understand the genetic pathways involved in this fascinating behaviour”.
This is a fantastic example of adaptation. Living largely in a dark environment and having an unprotected tail these snakes are able to roll into a bundle and cover up their most vulnerable part just by sensing light. In essence, it is seeing without eyes, which is quite a gift from evolution.
Source: University of Adelaide