How Sea Snakes Survive Without Water to Drink

Earth is awfully wet: about 70 percent of the planet is covered by deep, blue expanses of water. But to ocean-faring sea snakes, their briny habitat is an oxymoron: Home is a vast aquatic desert.

Creatures like the sea snake were thought to live completely independent of fresh water, by quenching their thirsts through some type of saltwater adaptation like other marine animals. But now researchers have discovered that one species, the yellow-bellied sea snake, in fact relies on rainfalls for drinking water, and in between rains is able to make do in an extreme state of dehydration.

Scientists have recently started questioning whether marine vertebrates, such as the sea snake, truly live independently of fresh water. Several species of animals, including sea turtles, bony fishes, dolphins and whales developed specialized adaptations to thrive in saltwater. For example, birds and some marine reptiles have salt glands to excrete excess salts from the water they drink. 

It was commonly believed that sea snakes adapted to their environment in a similar fashion. But several studies published within the past few years have shown a link between fresh water availability and the distribution of sea snake populations. The only sources of fresh water in the open sea are narrow bands of freshwater lenses that are known to form on the surface of the ocean following heavy rainfalls. Since sea snake populations are often concentrated around these bands of freshwater, researchers believed they depend on the water for survival.

If this was true, it must mean that sea snakes can survive extreme dehydration. To see if this was indeed the case, researchers captured 500 yellow-bellied sea snakes on the Guanacaste coast off of Costa Rica. They wanted to test if the snakes would drink fresh water immediately following capture. If the snake was thirsty, it was a good sign that it was also dehydrated.

The researchers dried the snakes off, weighed them and measured them before giving them fresh water to drink. They found that snakes tended to drink more following periods of low rainfall, and the lighter they were (and thus the more dehydrated they were), the more they drank.

Their findings show that sea snakes live in a dehydrated state for several months at a time, due to the length of the dry season on the Guanacaste coast (December through May or June). The researchers published their results this week in the journal Proceedings of the Royal Society B.

The results show both the tenacity and fragility of yellow-bellied sea snakes, and perhaps other marine snakes. Dehydration at sea could be a unique challenge to marine vertebrates like the sea snake, and may explain their rapidly declining populations in some parts of the world.

Further study of these thirsty reptiles could help scientists determine how changing precipitation patterns in tropical oceans will impact these animals.

Photo credit: RobHamm/Shutterstock

View the original article here

Japanese fish survive 5,000-mile trip across Pacific in tsunami boat

By Elaine Porterfield

SEATTLE | Fri Apr 12, 2013 10:55am EDT

SEATTLE (Reuters) - Scientists are baffled as to how a group of small fish native to Japan survived a journey across the Pacific after they were found on a boat swept away by the 2011 tsunami and washed up last month on the coast of Washington state.

The batch of striped beak fish - five in all - were discovered submerged in the hold of the 20-foot-long fishing skiff, dubbed the Sai-shou-maru, on Long Beach in southwestern Washington.

The vessel, found beached right-side-up, was confirmed this week to have originated from the region of northern Japan devastated in the immense tidal surge generated by the March 2011 Fukushima earthquake.

Other boats carried away by the tsunami have previously washed up along the U.S. Pacific Northwest and Alaska, as have chunks of piers and large quantities of other debris. But the fish found aboard the Sai-shou-maru are the first vertebrates - animals with backbones - known to have made the voyage.

Marine biologists studying the phenomenon are puzzled over precisely how striped beak fish, natural denizens of warmer, shallow southern Japanese waters, ended up as live stowaways in the well of the boat, and how they endured a two-year journey across the ocean.

"It is quite remarkable," Curt Hart, a spokesman for the Washington state Department of Ecology, told Reuters. "Everyone is very amazed that these fish survived for two years in that hold."

The fish were apparently swept up with the skiff as it was washed down the coast of Japan and out into the Pacific.

Scientists surmise that the fish made their home beneath the boat for much of the trip as it drifted upside down and partially submerged, feeding on other organisms that became encrusted or otherwise attached to the inverted vessel. Then they might have been scooped up into the skiff's hold when wind or waves righted the vessel, Hart said.

NOURISHMENT MYSTERY

The middle of the Pacific is far less rich in nutrients than coastal waters, raising questions of how the fish found enough food to survive the trip, said Jeff Adams, an expert at Washington Sea Grant, an agency supporting marine research.

The 6-inch-long striped beak fish, named for their protruding mouths and black-and-white striped markings, were the most surprising of an estimated 30 to 50 species of marine organisms that hitchhiked across the Pacific with the skiff.

Other stowaways included various types of algae, anemones, crabs, marine worms and shellfish.

Many were believed to be non-native species, and all were treated as potentially invasive - capable of displacing native organisms and disrupting the natural ecological balance if allowed to escape into the environment and propagate.

As a precaution, state officials swiftly removed the Sai-shou-maru from the shoreline before samples of organisms were collected for study, and the boat was scraped and steam-cleaned, Hart said.

Four of the fish found alive in the boat on March 22 have since died, and the lone surviving specimen has been moved to an aquarium in Seaside, Oregon.

The Sai-shou-maru is not the only Noah's ark of potential invasive species carried to the U.S. West Coast by the tsunami. Several more Japanese boats have washed ashore since last year in Washington, Oregon and California, and a fishing vessel found drifting off Alaska was scuttled by the Coast Guard.

Dozens of non-native and potentially invasive species - more than hitched a ride aboard the Sai-shou-maru - were previously found attached to two large hunks of piers that washed up, one in Oregon and one in Washington, Hart said.

(Editing by Steve Gorman, Cynthia Johnston and Patrick Graham)

View the original article here