May 4, 2009 -- Lizards may look lazy when basking in the sun, but the behavior serves a surprising purpose: They need vitamin D. Not only that, suggests a new study, the cold-blooded creatures manage their time in the sun with extreme precision for ideal vitamin D production. Like people, lizards have compounds in their skin that, with exposure to the sun's ultraviolet light, are converted to a useable form of the essential nutrient. "They were really, really good at hitting an optimum UV level," said Kristopher Karsten, a behavioral ecologist at Texas Christian University in Fort Worth. "It broadens our perspective of what they're really doing when they're sitting out there in the sun." Lizards get some vitamin D from their diet. The rest they get from the sun. Dosage is key: Not enough D and the animals may get sick, grow slowly, have trouble reproducing, or even die. Too much D is toxic. Related Content:
"It's a double-edged sword, where if they have too little, they're not going to do well, and if they have too much, they're not going to do well," Karsten said. "It's because there's an optimum amount associated with this that it interested us." For two months, Karsten and colleagues raised six panther chameleons inside in their lab. Three of the animals ate crickets that were dusted with vitamin D powder. The other three ate a cricket diet that was vitamin-D deficient. By the end of the period, the first group had far higher D levels than the second. Next, the chameleons were moved into round outdoor enclosures that measured about 6 feet wide and 6 feet tall. Each lizard's cage contained a plum tree or two as well as a black shade. The animals were free to move between sunny, UV-rich areas and shaded, low-UV areas. For 12 hours, from 7 a.m. and 7 p.m., the researchers noted how each lizard spent its time. As expected, the vitamin D-deficient chameleons exposed themselves to more UV-light than those who already had plenty of D. What was surprising was how precise the animals were about their behavior. The reptiles timed their basking sessions to achieve ideal levels of D. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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