Sea snakes evolved from highly venomous land snakes that returned to their ocean beginnings around 5 million years ago. Apparently, the familiar black and white patterns of these snakes not only work well in terrestrial camouflage (think zebra stripes), but it can also influence its susceptibility to algal fouling, which can reduce swimming speed by up to 20 percent. Here’s how:
“The fact that sea snakes have made the transition from terrestrial to aquatic life, makes them the perfect model to study evolution because we can compare traits between land snakes and sea snakes and hence identify selective forces unique to those habitats,” he said.
“The shift from land to water brought with it a new set of challenges, and sea snakes evolved unique physical traits which enabled them to survive in the aquatic environment — a paddle-shaped tail for swimming, valves to close their nostrils and large lungs to provide oxygen while under water.
“Another consistent attribute of sea snakes involves coloration: most are banded rather than unicoloured, blotched or striped. Fouling by algae has also been reported in several groups of sea snakes, and we wondered if maybe a snake’s colour could influence its susceptibility to this.”
“Once we knew there was a relationship between a snake’s colour and the amount of algal fouling, the next step was to determine if a snake’s dark colour was the actual cause of the higher algal levels,” Professor Shine said.
To do this, the researchers suspended plastic snake models — in black, white and black-and-white — in mid water and scored the amount of algal colonisation over the subsequent days. The results showed that colour directly affects the amount of algal growth, with black surfaces attracting the most algae, followed by black-and-white, and white the least.
“The spores of some marine algae settle out preferentially onto dark-coloured objects, which probably explains why the darker snakes hosted higher algal cover,” he said.
The finding raises the crucial question: if snake colour influences rates of algal accumulation, what are the consequences of such accumulation?
“The most obvious such consequence is increased drag and things became really interesting when we tested to see if algal cover affected a snake’s swimming speed. Our locomotor trials revealed a 20 percent reduction in swimming speeds in snakes covered with a heavy coating of algae.”