Effects of Sex and Whole Life Cycle UVB Irradiation on Performance and Mineral and Vitamin D3 Contents in Feeder Crickets (Gryllus bimaculatus)

Abstract

Captive insectivore nutrition is challenging due to the differing nutritional profiles of wild and captive diets and an incomplete understanding of both. Ultraviolet B (UVB)-irradiation has recently been explored as a means of improving prey-insect vitamin D3 and Ca content. Although short-term irradiation has been successful in some species, it has been unsuccessful in black field crickets (Gryllus bimaculatus)—a commonly cultured feeder insect. We exposed crickets to UVB irradiation from hatchling to adult stages and measured the vitamin D3 and mineral contents of crickets by sex. We did not detect vitamin D3 (detection limit 0.5 iU/g) or an effect of UVB irradiation on mineral content under either UV+ or UV− conditions. We identified large differences between sexes in Ca, K, Mg and P (females higher) and Cu, Fe, S and Zn (males higher), likely linked to reproductive investment. The differences do not straddle the minimum recommended concentrations of minerals for vertebrate growth and thus may be most relevant to animal nutrition in contexts of particular sensitivity or need. We demonstrate a UV-linked trade-off in cricket performance between individual cricket size and the numbers of crickets produced and characterise the energy costs associated with UVB provision. Our results do not support the use of UVB lighting for G. bimaculatus to improve nutrition but demonstrate previously unreported differences in the nutritional profiles between sexes in this species.