| It has been postulated that some source of vitamin D is required by all vertebrates to maintain adequate circulating calcium and skeletal health. Vitamin D may be synthesized in the skin upon exposure to ultraviolet-B radiation or ingested in the diet. Chiroptera, the second most speciose group of mammals, are primarily nocturnal and have a highly varied diet, thus considerable variation in vitamin D status can be expected. Little is known about the role of vitamin D in these organisms.; Chosen for this study were five New World, cave-roosting species ( Artibeus jamaicensis, Brachyphylla cavernarum, Monophyllus redmani, Noctilio leporinus, and Desmodus rotundus) represented by contrasting feeding habits (2 frugivores, 1 nectarivore, 1 piscivore and 1 sanguivore), and two Old World frugivores, one of which typically roosts in foliage (Pteropus hypomelanus) and another that roosts in caves (Rousettus aegyptiacus). A competitive protein-binding assay (CBPA) was used to evaluate 25-hydroxyvitamin D [25(OH)D], the major circulating metabolite, and high-performance liquid chromatography (HPLC) was used to evaluate circulating vitamin D2/D 3.; Results indicate that circulating 25(OH)D is extremely high in free-ranging species that consumed animal tissue (fish or blood) but extremely low in free-ranging species that consumed fruit and/or nectar. Results also indicate that both P. hypomelanus and R. aegyptiacus were capable of synthesizing vitamin D3 in their skin when exposed to daily sunlight. The efficiency of synthesis varied however, possibly reflecting the relative amount of skin pigmentation. Results also indicate that these two species poorly absorb a single highly concentrated oral vitamin D2/D 3 supplement, but repeated administration of a similarly concentrated supplement was successful in increasing 25(OH)D in R. aegyptiacus . Finally, the results suggest that P. hypomelanus discriminates against vitamin D3 in favor of vitamin D2. However, due to small sample size the latter results are inconclusive.; Bats are a diverse group and this is reflected in their vitamin D status. In species naturally exposed to sunlight, endogenous vitamin D3 synthesis may be important for calcium homeostasis and bone health. However, in herbivorous, nocturnal species calcium homeostasis may require only minimal amounts of vitamin D or may function entirely independent of this substrate. |
