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 D3. 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 D3 diet for 6 weeks than when subsequently fed a high dietary vitamin D3 diet for 6 weeks. When we returned the anole's diet to the low vitamin D3 regimen for a third 6-week period, UVB exposure remained lower than in the first 6-week period. This suggests an initial UV photo-regulatory adjustment to high dietary vitamin-D3 but a slow return to greater reliance on UVB-induced endogenous vitamin D3 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 D3. The response of A. sagrei in the laboratory to visible light without UVB was similar to their response to visible light with UVB. Therefore, the anoles appeared to be responding primarily to visible light. Anolis lineatopus may be unable to use dietary vitamin D3 to restore low vitamin D status.Abstract
Schematic diagram of laboratory enclosure showing UVB exposure zones during UV-light treatments of captive Anolis lizards. The unshaded zone indicates high UVB exposure; the light gray zone, medium UVB exposure; the dark gray zone, low UVB exposure. See text for details. The dashed line illustrates a thermal gradient zone. From the cage floor to the line, ambient temperature ranged from about 40–25°C throughout the cage. Above the line, temperature was uniform laboratory temperature and ranged from 23–25°C.
UVB exposure of free-living Jamaican Anolis at the Hofstra University Marine Laboratory, St. Anns Parish, Jamaica in March 2004. There was a species effect but no sex–size category effect (see text).
Mean number of voluntary exposures of six Anolis sagrei and six Anolis lineatopus to a light source (UVB on or off) during each of three sequential 6-week periods (A), (B), (C) during which dietary vitamin D3 was changed from low to high and back to low. Capped vertical lines above the bars are one standard error. There were 72 possible exposures for each of the three periods with the UVB source on or off. There was significant variation among the periods only for A. sagrei (see text).
Mean UVB dose for six Anolis sagrei and six Anolis lineatopus received when they voluntarily exposed themselves to medium or high exposure from the UVB source during each of three sequential 6-week periods (A), (B), (C) and also during the total 18-week experiment. There was significant variation among the periods only for A. sagrei (see text).
Percent photoproduct production within in vitro models exposed to two UVB sources with the same average irradiance. The irradiance was measured with a Solartech 6.5 broadband UVI meter for both the sun and for a Westinghouse FS-20 sunlamp. The regressions are different (see text).
Irradiance of UVB as a function of irradiance of visible sunlight at locations where Anolis sagrei were discovered in the field at Jamaica in March 2004.The regression is significant (P < 0.001).
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