Ultraviolet Exposure and Vitamin D Synthesis in a Sun‐Dwelling and a Shade‐Dwelling Species of Anolis: Are There Adaptations for Lower Ultraviolet B and Dietary Vitamin D₃ Availability in the Shade?

Abstract

We compared the natural ultraviolet B (UV-B) exposure, dietary vitamin D, and skin-generated vitamin D synthesis for adult males of two species of Jamaican anoles. The more shade-tolerant and thermal-conforming Anolis lineotopus merope, rarely exposed to full sun, experienced less UV-B irradiation in its shady environment than the more heliophilic and thermophilic Anolis sagrei, which frequently basked in full sun during the morning hours (0800-1100 hours). Both species obtained detectable levels of vitamin D(3) in their diet, but the heliophilic A. sagrei obtained more. To compensate for less availability of UV-B and dietary vitamin D, the skin of A. lineotopus merope seems to have acquired a greater sensitivity than that of A. sagrei regarding UV-B-induced vitamin D(3) photobiosynthesis. We assessed this by observing a greater conversion of provitamin D to photoproducts in skin exposed to UV-B from a sunlamp. The reduced skin sensitivity of A. sagrei regarding vitamin D photobiosynthesis may reflect a correlated response associated with less need for vitamin D photobiosynthesis and greater need for UV-B screening capacity as an adaptation to a more damaging UV-B environment. However, the possibility that adaptations for photobiosynthesis of vitamin D and for protection from skin damage could involve independent mechanisms needs investigation. Also, the ability to behaviorally regulate UV-B exposure, as shown for the panther chameleon, would benefit both species of Anolis and should be investigated.

Voluntary exposure of some western‐hemisphere snake and lizard species to ultraviolet‐B radiation in the field: how much ultraviolet‐B should a lizard or snake receive in captivity?

“…3) and the time of day [Fig. 4;Ferguson et al, 2005]. Therefore, the comparisons here may or may not use complete species-or population-typical values, which can only be determined by all-day, season-long studies.…”

“…To our knowledge this is among the first reports quantitatively estimating natural UVB-exposure of lizards and snakes [see also Carman et al, 2000;Ferguson et al, 2005]. Based on the natural UVB exposure levels of 15 species of snakes and lizards from the southern and western U.S. and Jamaica, general recommendations of average and range of levels of exposure (irradiance) are presented for species occupying certain types of light environments (Table 1).…”

Low Vitamin D Status despite Abundant Sun Exposure

“…However, in our study the population was predominantly young, which should have obviated such reduced capability for vitamin D synthesis. Importantly, lizards with behaviorally high sun exposure have a lower capacity to produce vitamin D than closely related species with habitually less sun exposure (36). Thus, it appears likely that factors exist, which are not yet well understood, that can restrict skin production of vitamin D in response to UV radiation.…”

Vitamin D supplementation increases the attractiveness of males' scent for female Iberian rock lizards

“…Vitamin D 3 is essential in calcium metabolism of lizards and other vertebrates (Allen et al 1994;Laing & Fraser 1999). However, very often, the synthesis of vitamin D 3 in the skin is not sufficient to meet physiological requirements, and lizards require dietary intake of vitamin D (Allen et al 1994;Ferguson et al 2005). Under these conditions, vitamin D is an essential nutrient for lizards.…”