Study: Lizards bask for more than warmth

Apr 20, 2009

Keeping warm isn't the only reason lizards and other cold-blooded critters bask in the sun. According to a study published in the May/June issue of Physiological and Biochemical Zoology, chameleons alter their sunbathing behavior based on their need for vitamin D.

"It's a longstanding assumption that thermoregulation is the only reason that lizards bask," says Kristopher Karsten, a biologist at Texas Christian University who led the study. "Our results suggest that in addition to thermoregulation, vitamin D regulation appears to have a significant impact on basking behavior as well."

Chameleons, like humans and most other vertebrates, get vitamin D in two ways: They can absorb it from food, and they can produce it in their skin. In order to produce vitamin D, however, the skin must be exposed to .

To test whether chameleons alter their sunning behavior based on dietary vitamin D intake, Karsten observed the behavior of two different groups of chameleons. One group had high internal vitamin D levels, thanks to a diet of dusted with a vitamin D powder. The other group ate regular crickets and had low vitamin D. The chameleons were then placed in individual outdoor enclosures that offered open area for direct sun, and a tree to offer filtered sun and shade.

Chameleons generally move from sun to shade throughout the day. But Karsten found that chameleons fed the low vitamin D compensated by increasing their exposure to the sun's UV rays. Chameleons with high vitamin D diets, on the other hand, limited their UV exposure.

"It appears that panther chameleons have the ability to gauge their internal vitamin D levels and alter their basking behavior accordingly," Karsten says.

And they do it with remarkable accuracy.

"The chameleons were as effective as mathematically possible by our methods at regulating toward optimal UV exposure for their vitamin D profile," he says. "We thought they were probably pretty good at regulating their UV exposure; we just didn't think they'd be this good."

It's not clear, however, by what mechanism they are able to sense their internal vitamin D levels, but Karsten thinks there may be a brain receptor sensitive to the vitamin.

"Given the ability for panther chameleons to precisely, accurately and effectively adjust basking behavior as a direct result of vitamin D3, [a brain receptor] seems likely to occur in panther chameleons."

More information: Kristopher B. Karsten, Gary W. Ferguson, Tai C. Chen, and Michael F. Holick, "Panther Chameleons, Furcifer pardalis, Behaviorally Regulate Optimal Exposure to UV Depending on Dietary Vitamin D3 Status," Physiological and May/June 2009.

Source: University of Chicago (news : web)

Explore further: Dogs hear our words and how we say them

add to favorites email to friend print save as pdf

Related Stories

Variant of vitamin D receptor gene linked to melanoma risk

Sep 22, 2008

A new analysis indicates an association between a gene involved in vitamin D metabolism and skin cancer. Published in the November 1, 2008 issue of Cancer, a peer-reviewed journal of the American Cancer Society, the study ...

'Let the sunshine in' to protect your heart this winter

Nov 17, 2008

The temperature might not be the only thing plummeting this winter. Many people also will experience a decrease in their vitamin D levels, which can play a role in heart disease, according to a new review article in Circulation.

Recommended for you

Dogs hear our words and how we say them

57 minutes ago

When people hear another person talking to them, they respond not only to what is being said—those consonants and vowels strung together into words and sentences—but also to other features of that speech—the ...

Amazonian shrimps: An underwater world still unknown

2 hours ago

A study reveals how little we know about the Amazonian diversity. Aiming to resolve a scientific debate about the validity of two species of freshwater shrimp described in the first half of the last century, ...

Factors that drive sexual traits

3 hours ago

Many male animals have multiple displays and behaviours to attract females; and often the larger or greater the better.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

deatopmg
not rated yet Apr 22, 2009
@organicfood; a better (the best) source of D3 info is at http://www.vitamindcouncil.org

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.