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

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New Drink Trends, Decoded

When you're feeling parched, you know that reaching for an ice-cold water, juice or tea is better for you than slurping a fatty milk shake or jumbo soda. But these days, there are so many beverages billed as healthful. They contain hot new ingredients—such as kombucha, matcha and chia (huh?)—or promise big-time perks, from boosting your immunity to revving your energy. So do these It drinks stand up to their claims? We put the question to top registered dietitians, so that you can start sipping smarter.

Enhanced waters

The trend H2O? More like H2—Whoa! Newfangled blends, like coconut, vitamin, flavored and alkaline waters, promise better, more nourishing hydration than plain agua.

The real scoop Be skeptical about any water claiming to boost your immune system or energy. "Antioxidants, vitamins and amino acids are best absorbed through whole food and 100 percent natural fruit and dairy—not fortified—drinks," says Janet Helm, RD, founder of Nutritionunplugged.com.

What about coconut water, which is often touted as an all-natural improvement on sports drinks? "It's a great source of potassium but doesn't contain enough sodium to be an effective post-workout drink," says Heather Mangieri, RD, spokesperson for the Academy of Nutrition and Dietetics. If you guzzle it after exercising, try pairing it with a salty snack, like a 100-calorie pretzel pack.

As for alkaline water, the buzzed-about beverage that is said to even out the body's pH levels: "There's no real benefit," says Marjorie Nolan Cohn, RD, author of The Belly Fat Fix. "We balance pH naturally."

Sip or skip? "Bottom line, Americans aren't drinking enough water," says Helm. "If you like these new varieties better than regular water, go ahead." Just scan the nutrition facts before you chug, since—unlike tap water—the enhanced versions aren't always calorie-free. (Also, check out "3 Ways to Spa-ify Your Water," for extra flavorful, low-calorie H2O that you can make at home.)

Juice mania

The trend Sales of bottled superpremium fruit and veggie drinks, like the kind you find at Whole Foods or juice bars, have increased nearly 64 percent since 2004, according to the research firm Beverage Marketing Corporation. Green juices—which are made of kale, spinach, parsley and other veggies—and chia-seed add-ins are particularly popular with celebrities, as well as the health-obsessed among us.

The real scoop Downing juiced fruits and vegetables can make it easier to reach the recommended 4½ cups of produce a day. (Yep, pure juice counts toward your daily quota.) That said, "during juicing, the fiber-containing pulp can get left behind," and serious nutritional benefits along with it, says registered dietitian Christine Gerbstadt, MD, author of Doctor's Detox Diet. And while chia does provide protein, fiber, calcium and good-for-you omega-3 fatty acids, it's not a great source of all omega-3s. "Chia seeds contain alpha-linolenic acid," Mangieri explains. "The body converts ALA into types of omega-3 called DHA and EPA, but not very efficiently, so it's not clear how much the body absorbs."

Sip or skip? "Eating vegetables is always healthier than drinking them," Dr. Gerbstadt says. If you do go the juice route, know it's not always light: An 8-ounce serving can hold up to 200 calories. So check the ingredient list not only for sugar, but also for juice concentrate, nectar, fruit puree, fructose, cane extract, sucrose, maltose, agave and honey—they're just different words for the sweet stuff. "Make sure it's not one of the first five ingredients," Dr. Gerbstadt adds.

Souped-up iced teas

The trend Move over, black and green. Now there's a tea for whatever ails you: kombucha to aid digestion and boost immunity, matcha to rev metabolism and yerba maté for weight loss—at least according to what the marketing says.

The real scoop If you can stomach the vinegary taste, kombucha—made from fermented black tea—provides a serving of probiotics that may help ease digestion and support immune health, Helm says. The drink, she adds, can be a great nondairy alternative for people.

Matcha, a green-tea powder sold as a supplement or mixed into drinks, packs an antioxidant punch—more so than regular brewed green tea, since you're consuming the entire tea leaf. "There have been claims that it boosts metabolism," Helm says. "But a 15-minute walk will do more to burn calories." And despite what you might have heard, yerba mate isn't effective at reducing body weight, a review in The American Journal of Clinical Nutrition concluded.

Sip or skip? When it comes to kombucha, stick to one 16-ounce bottle a day: Store-bought kombucha can contain trace amounts of alcohol due to the fermentation process, though these levels are regulated by the FDA. (Steer clear of home-brewed kombucha, which has reportedly been linked to side effects ranging from nausea to toxicity.) Or simply add ice to a black, green or herbal tea.

All-natural energy drinks

The trend Last year, energy drinks outsold bottled water, according to the Beverage Industry 2012 State of the Industry Report. Giving the category a boost: so-called natural energy drinks, made from herbs and vitamins—as well as caffeine, often sourced from green tea.

The real scoop While all-natural energy drinks are also fueled by caffeine, they boast a mild 50 to 90 mg per serving—enough to get you going without giving you the jitters. (By comparison, a tall Starbucks Pike Place Roast serves up 260mg.) "If a 3 p.m. cup of joe keeps you wide-eyed at bedtime, an all-natural energy drink can perk you up without keeping you up," Cohn says. Another bonus: Such drinks contain relatively little sugar and fewer calories than regular juice, sports drinks or soda.

Sip or skip? Stay away from energy drinks labeled as dietary supplements: They are not required to be proved safe by the FDA before they hit the market. In fact, more than 20,000 emergency room visits in 2011 were linked to energy drink consumption.

Whether it's energy beverages or coffee you're drinking, limit your caffeine intake to 500mg per day. Or choose water, which can be a better option if you feel your energy is flagging. "Dehydration exacerbates fatigue," Cohn notes. Score yet another one for Mother Nature's original beverage.

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