Do panther chameleons bask to regulate endogenous vitamin D3 production?
Basking by ectothermic vertebrates is thought to have evolved for thermoregulation. However, another beneficial effect of sunlight exposure, specifically the ultraviolet B (UV-B) component, includes endogenous production of vitamin D(3). In the laboratory, panther chameleons exhibited a positive phototaxis to greater visible, ultraviolet A (UV-A) and UV-B light. However, with equivalent high irradiances of UV-A or UV-B, their response to UV-B was significantly greater than it was to UV-A. Exposure of in vitro skin patches of panther chameleons to high UV-B (90 microW/cm(2)) for 1 h significantly enhanced vitamin D(3) concentration. Voluntary exposure to higher UV-B irradiance (70 vs. 1 microW/cm(2)) resulted in greater circulating 25-hydroxyvitamin D(3) in female panther chameleons (604 vs. 92 ng/mL). Depending on dietary intake of vitamin D(3), chameleons adjusted their exposure time to UV-B irradiation as if regulating their endogenous production of this vital hormone. When dietary intake was low (1-3 IU/g), they exposed themselves to significantly more UV-producing light; when intake was high (9-129 IU/g), they exposed themselves to less. Vitamin D(3) photoregulation seems to be an important additional component of the function of basking.
Ferguson
Gary W
GW
Department of Biology, Texas Christian University, Fort Worth, TX 76129, USA. g.ferguson@tcu.edu
Gehrmann
William H
WH
Karsten
Kristopher B
KB
Hammack
Stephen H
SH
McRae
Michele
M
Chen
Tai C
TC
Lung
Nancy P
NP
Holick
Michael F
MF
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002762:Cholecalciferol / Q000096:biosynthesis* / Q000097:blood; D004032:Diet; D005260:Female; D008116:Lizards / Q000097:blood / Q000502:physiology*; D008297:Male; D013472:Sunlight; D014466:Ultraviolet Rays
D002762:Cholecalciferol