Sensitive sea snakes are sexier

In honour of World Ocean Day, here’s a nice little story about…sea snakes, sex and sensitive males.

In a new paper, published in the Biological Journal of the Linnean Society, researchers from the University of Adelaide, University of Melbourne and colleagues detail the enlarged touch receptors that help turtle-headed sea snakes (Emydocephalus annulatus) find and woo their mates.

The ritual of snake love is a little different on land than it is in water – up here, snakes use tongue-flicking to sense sex pheromones left by other snakes and can follow these trails. Of course, pheromones are diluted in water and so quite hard to perceive.

“What’s more, turtle-headed sea snakes can’t see very clearly underwater; they’ve been known to court anything long and dark, including sea cucumbers,” says Jenna Crowe-Riddell from the University of Adelaide, who led the study.

“To make matters worse, once a female is found the male must overcome buoyancy force so he doesn’t float away from his potential mate.”

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Animal magnetism is real

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So, the researchers found that sea snakes use a different sense to spice up their sex lives – and it is quite touching.

“Most snakes have thousands of touch receptors all over their face that look like a dusting of freckles,” says Crowe-Riddell.

“These touch receptors have become much larger in sea snakes, potentially to sense vibrations made by swimming mates, prey or predators.

“When we took a closer look at museum specimens, we discovered male turtle-headed sea snakes have larger touch receptors overall than females. We also found mature males have enlarged scale structures on their snout and chin, and their cloaca – an all-purpose hole used for reproduction and excretion.”

The team used microscopy to study specimens from the Australian Museum, the Art Gallery of Northern Territory and the Western Australian Museum. They found that the scale structures on the chin and cloaca have specially evolved touch receptors, which may provide feedback through touch and vibration sensations.

They suggest the chin structures may help the snake orient its head in the direction the female was swimming, and the cloaca receptors may help the snake get in position for successful intimacy.

“We think these receptors evolved to help males maintain the correct points of contact with the female during mating, which is a tricky task when you’re a tube-shaped limbless snake,” said Crowe-Riddell.

But when making love, these sultry males don’t neglect foreplay, it seems. The team also found that the males have a spine-like structure on its snout called the ‘rostral spine’, which is used for some arousing prodding.

“The rostral spine may be used to stimulate the female,” says Crowe-Riddell. “Such types of tactile foreplay are thought to be important for mating in snakes because they can cause beneficial hormonal changes and receptive behaviours in females.”

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“Reptiles are not typically appreciated for their intimate interactions, but our research is revealing that sea snakes have fascinating tactile adaptations for intra-species communication.”

Even though life in the ocean can be hard, this new research does paint a picture of how ocean-dwellers might evolve to overcome the difficult pursuit of love (and sex).

“As we build a more complete picture of underwater perception, sea snakes are becoming a fantastic example of how evolution creates opportunity from constraints,” says Crowe-Riddell.

Turtle-headed sea snakes getting down to business. Credit: Jenna Crowe-Riddell and team.