Australasian Science: Australia's authority on science since 1938

Sea Snakes Have Extra Sense

The move from life on land to life in the sea has led to the evolution of a new sense for sea snakes, according to a study published in Open Biology(http://tinyurl.com/zhmorpu).

“Land snakes and many lizards have small raised structures on the scales on their heads – called scale sensilla – that they use to sense objects by direct touch,” says lead author Jenna Crowe-Riddell of The University of Adelaide. “We found that the scale sensilla of sea snakes were much more dome-shaped than the sensilla of land snakes, with the organs protruded further from the animals’ scales, potentially making them more likely to be able to sense vibrations from all directions. We also found that scale sensilla on some of the fully aquatic snakes covered a much higher proportion of the scales’ surface.

“We believe sea snakes use these organs to sense objects at a distance by ‘feeling’ movements in the water.”

The researchers looked at 19 species of snakes, including aquatic, semi-aquatic and land species, and measured the coverage of sensilla over single scales on their heads. They used DNA sequencing to reconstruct the evolutionary relationships between the snakes, which evolved from land snakes 9– 20 million years ago, and used microscope imaging and specially developed software to automatically detect the small organs from silicone casts of snake heads. They also examined the shape of the sensilla using scanning electron microscopy.

“What we now need to do”, says lead scientist Dr Kate Sanders, “is to investigate the physiology of these scale sensilla and demonstrate exactly what they can sense. If they are hydrodynamic tactile sense organs, as we suspect, then by comparing them to the scale sensilla of closely related land snakes we can start to understand how evolution has changed these organs from direct-touch sensors to distance vibration sensors that work underwater.”

The researchers believe that the ability to sense vibrations underwater would imply that human disturbances such as motor boats and seismic surveys would have potential impacts on sea snake populations.