Vitamin D3 is essential for good health, yet seldom can animals obtain enough of it from food. Fortunately, exposure to sunlight supplements the diet: ultraviolet B (UVB) rays convert a cholesterol-related molecule that’s present in skin cells into vitamin D3. Balancing the two sources might seem tricky, but a recent paper shows that chameleons are amazingly good at it.
Most people think reptiles bask in the sun just to warm up. To establish whether they also do it to get their vitamins, Kristopher B. Karsten and his graduate adviser at the time, Gary W. Ferguson of Texas Christian University in Fort Worth, along with two colleagues, studied panther chameleons, Furcifer pardalis. For two months, the team fed six chameleons crickets that were either enriched or low in vitamin D3. The team then set the chameleons in separate outdoor enclosures that had similar amounts of sun and shade for five days, and tracked where they spent their time. The three vitamin-deprived chameleons spent more time in the sun than did their three vitamin-fortified counterparts.
That behavior led to a mathematically optimum exposure to UVB, particularly in the vitamin-deprived bunch, the researchers calculated. The chameleons are thus pros at balancing diet and sunshine. The researchers suspect that a special brain receptor lets the reptiles determine when they’re low on D3 and how much sunning will make up for it. (Physiological and Biochemical Zoology)
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This article was provided to LiveScience by Natural History Magazine.