Sea snakes are an evolutionary success story. With about 70 species, they’re the most diverse reptile group in the ocean, outnumbering sea turtle species 10-to-1. They sport a range of physical adaptations for life at sea, including a flattened oar-like tail for paddling and the abilities to smell underwater, hold their breath for hours and go for months without a drink. And although they’re not powerful swimmers, they have spread throughout the Pacific and Indian Oceans, ranging from Japan to New Zealand and from South Africa to Central America.
(From Science Daily) — But there is a glaring gap in sea snakes’ near-global distribution: the Atlantic Ocean.
“Why there are no sea snakes in the Atlantic is a question we’ve been asking for a long time,” said Coleman Sheehy, Florida Museum of Natural History herpetology collection manager. “We know why they are where they are. But why they’re not where they’re not has been a mystery.”
Theoretically, sea snakes could flourish in the Atlantic: Warm, tropical regions such as the Caribbean offer prime sea snake habitat and living conditions.
The problem, according to Sheehy and his colleagues, is that the snakes can’t get there.
In a paper published in Bioscience, lead author Harvey Lillywhite of the University of Florida’s department of biology, Sheehy and their co-authors chalk up the absence of sea snakes in the Atlantic to geography, climate and timing.
Sea snakes evolved in the Coral Triangle region of Southeast Asia 6 to 8 million years ago, with the majority of species appearing between 1 and 3 million years ago. By the time any sea snakes spread across the Pacific to the New World, the Isthmus of Panama had already closed, blocking their access to the Caribbean.
In the Eastern Hemisphere, forbiddingly cold, dry conditions at the tip of South Africa where the Indian and Atlantic Oceans meet prevent the snakes from surviving long if they drift west of the Cape of Good Hope. The snakes die in water colder than 65 degrees, and they depend on the freshwater of rivers, streams, estuaries and rainfall for drinking water, a finding that Lillywhite and Sheehy published in 2014.
Could snakes find a way around these barriers to gain a foothold in the Atlantic?
Not likely, Sheehy said. The species that has the best shot is the yellow-bellied sea snake, whose distribution is broader than any other snake or lizard on the planet. While a few individual yellow-bellied sea snakes have been reported on the Caribbean coast of Colombia — likely drifters who made it through the Panama Canal — Sheehy said the odds are stacked against them establishing a successful breeding population.
If they did, “nothing in the Atlantic would be prepared,” he said. “Prey wouldn’t know how to protect themselves, and …
Read the full article here: https://www.sciencedaily.com/releases/2017/11/171129143343.htm