Vitamin D3 in the hemolymph of goliath birdeater spiders (Theraphosa blondi).

Vitamin D3 is an important vitamin in vertebrates. This fat-soluble vitamin is associated with the regulation of many physiologic processes, most importantly calcium metabolism. The presence or importance of vitamin D3 has been determined in only a handful of invertebrate species. In this study, hemolymph was collected from six wild-caught, subadult goliath birdeater spiders (Theraphosa blondi) and analyzed for the presence of 25(OH)-vitamin D3, the precursor to the active form of vitamin D3. The metabolite 25(OH)-vitamin D3 was detected in all of the spiders (mean: 5.7 nmol/L, SD: 1.5 nmol/L, range: 3-7 nmol/L). The method by which spiders acquire vitamin D3 is unknown. It is possible, though unlikely, that they synthesize it via exposure to ultraviolet radiation. Many of the invertebrate species upon which theraphosid spiders prey are not known to have high circulating levels of vitamin D3 or its precursors. However, dietary intake is a possible means of vitamin D3 acquisition in this study.