PRELIMINARY-OBSERVATIONS ON THE RELATIONSHIP OF CALCIUM INGESTION TO VITAMIN-D STATUS IN THE GREEN IGUANA (IGUANA-IGUANA)

We hypothesized that vitamin D-deficient green iguanas with depleted c alcium stores would seek to augment calcium intake by self-selection o f a high calcium source. Eight green iguanas were offered free-choice ground oystershell in addition to their regular diet. Of these, two ha d not been exposed to ultraviolet (UV-B) radiation for >5 years and we re demonstrated to be vitamin D-deficient by low circulating levels of the principal vitamin D metabolite, calcidiol (25-hydroxy-cholecalcif erol). The six others had been exposed to a UV-B emitting bulb for the previous 3 years and had high circulating calcidiol levels. Average d aily food intake (expressed as dry matter per kg body mass) did not di ffer between the Low-D and High-D iguanas. The daily oystershell intak e of the Low-D iguanas (0.02-0.03 g/kg) was lower than that of the Hig h-D iguanas (0.06-0.70 g/kg), leading to a significant difference in c alcium intake. The failure of iguanas to increase calcium intake in re sponse to vitamin D-deficiency was puzzling and suggests that vitamin D, as a steroid hormone, may play some role in the expression of calci um appetite. (C) 1997 Wiley-Liss, Inc.