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Study: Lizards bask for more than warmth
April 21, 2009Keeping 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 UV radiation.
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 crickets 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 diet 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 vitamin D receptor] seems likely to occur in panther chameleons."
University of Chicago Press Journals
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 crickets 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 diet 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 vitamin D receptor] seems likely to occur in panther chameleons."
University of Chicago Press Journals
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Future smart mobile has to be a true chameleon
By continously adapting the receiver settings of a mobile phone to the current conditions, the advantage is twofold; facing bad reception, the connection can be improved while in good conditions, the energy consumption can be reduced. This is possible by an automatic controller developed by Lodewijk Smit of the University of Twente in The Netherlands. Smit did his PhD work on this, within the Centre of Telematics and Information Technology (CTIT). The mobile connection can be optimized by frequently evaluating the quality and adapting the receiver of the mobile device to this level. The conditions are continuously changing. Hence, the quality of the reception is fluctuating. Modern phones wi
Chameleon particles from the Sun
The Sun emits electron-neutrinos, elementary particles of matter that have no electric charge and very little mass, created in vast numbers by the thermonuclear reactions that fuel our parent star. Since the early 1970s, several experiments have detected neutrinos arriving on Earth, but they have found only a fraction of the number expected from detailed theories of energy production in the Sun. This meant there was either something wrong with our theories of the Sun, or our understanding of neutrinos. It turns out that our theories of how the Sun is powered look like being correct according to a team of scientists from the UK, the US and Canada whose latest results from research into solar
Going Ballistic: Soft Structures Could Spell The End For Slow Shrimps
Many animals are able to rapidly extend their tongues to catch prey. In fact, the chameleon extends its tongue at an acceleration rate of 500 metres per second square - generating 5 times the G force experienced by an F-16 fighter during its most demanding maneouvre! New research presented at the Society for Experimental Biology conference in Swansea today has shed light on exactly how these remarkable feats are achieved. Dr Johan van Leeuwen of Wageningen University, the Netherlands, suggests that these `ballistic movements` are possible due to nature`s remarkable `soft body mechanics`. In research which has studied the bullet-like extension of squid tentacles and snake and chameleon tongue
Nature press release for 14 February issue
[415787] EVOLUTION: BATTLE OF THE SEXES (pp787-789) As Valentines Day hoves into view, think on this: the toilet seat up or down debate is, metaphorically, going on all over the animal kingdom. Evolutionary conflicts of interest between the sexes occur in many animal species, and may result in an 'arms race' between males and females, as illustrated on the cover of this week`s Nature, which shows a male and a female water strider (Gerris lacustris) engaged in a violent pre-mating 'wrestling match'. The battle of the sexes can lead to an evolutionary standstill. The advantage gained by one sex is matched by analogous counteradaptations in the other sex, but examples of this in action are hard
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