Solving the mystery of sea snakes that cannot drink seawater

One of the yellow-bellied sea snakes
© Mark Sandfoss, University of Florida

Sea snakes are surrounded by seawater. While previously scientists believed they could drink seawater, new research has shown they need to access fresh water.

The leader of the study, Harvey Lillywhite, a professor of biology of the University of Florida, said: “This study contributes to a fuller understanding of how pelagic sea snakes, and possibly other marine animals, avoid desiccation following seasonal drought at sea.”

The new study has been published in PLOS one. It shows that sea snakes living in drought areas relieve their dehydration as soon as the wet season hits.

What is the yellow-bellied sea snake?

  • The yellow-bellied sea snake, or hydrophis platurus, is the only reptile in the order Squamater that lives on the open sea;
  • It has one of the largest geographic ranges of any vertebrate; and
  • It has no access to fresh water during the dry season.

So how does the yellow-bellied sea snake survive in drought regions? This seems to be based upon access to fresh water “lenses” that form on the surface of the ocean during periods of heavy rain, but there is little known about how marine vertebrates consume rainfall.

The team captured 99 sea snakes off the coast of Costa Rica. They offered them freshwater in a laboratory environment. They were there just as six months of drought broke and the rainy season began. Only 13 percent of snakes who they captured after the rainfall began accepted their offer of freshwater. However, 80 percent of the sea snakes captured before the rainy season began accepted the freshwater offered by the researchers. This suggests that the rainfall relieved their dehydration.

The decline of sea snakes

Lillywhite added: “How these animals locate and harvest precipitation is important in view of the recent declines and extinctions of some species of sea snakes.”

The biggest remaining question is how will climate change impact sea snakes? The changes to precipitation due to climate change are an important consideration for the yellow-bellied sea snake, since it appears to survive based on fresh water “lenses” from heavy rain.

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