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.