Ultraviolet Light Exposure and Response to Dietary Vitamin D3 in Two Jamaican Anoles

In Jamaica, free-living male and female-sized Anolis sagrei are exposed to more natural ultraviolet-B (UVB) from sunlight than male and female-sized Anolis lineatopus. In the laboratory, we tested predictions derived from the hypothesis that Anolis possess a mechanism for behaviorally photo-regulating their exposure to UVB depending on their dietary intake of vitamin D-3. Anolis sagrei voluntarily exposed themselves more frequently to visible and UVB light and received higher doses of UVB in an artificial light gradient when fed a low vitamin D-3 diet for 6 weeks than when subsequently fed a high dietary vitamin D-3 diet for 6 weeks. When we returned the anole's diet to the low vitamin D-3 regimen for a third 6-week period, UVB exposure remained lower than in the first 6-week period. This suggests an initial UV photoregulatory adjustment to high dietary vitamin-D-3 but a slow return to greater reliance on UVB-induced endogenous vitamin D-3 production. Conversely, while exposing themselves to UVB with similar frequency and doses as A. sagrei over the course of the 18-week experiment, A. lineatopus did not show the same decreased attraction to visible and UVB light in response to increased dietary vitamin D-3. The response of A. sagrei in the laboratory to visible light without UVB was similar to their response to visible light with LTVB. Therefore, the anoles appeared to be responding primarily to visible light. Anolis lineatopus may be unable to use dietary vitamin D-3 to restore low vitamin D status.