The nocturnal leopard gecko (Eublepharis macularius) uses UVb radiation for vitamin D3 synthesis.

Vitamin D is an important regulator of calcium and phosphorus homeostasis in animals. It can be acquired from the diet or synthesised de novo when skin is exposed to UVb. Vitamin D deficiency can lead to a complex of diseases collectively called metabolic bone disease (MBD). Diurnal lizards without access to UVb are prone to develop vitamin D deficiency, even when dietary vitamin D3 is provided. A trial was conducted to determine whether juvenile nocturnal lizards require access to UVb to prevent vitamin D deficiency. All leopard geckos (Eublepharis macularius) were supplemented with dietary vitamin D3. One group was exposed to low level UVb radiation (33-51 µW/cm2) from hatching until 6 months of age and a second group remained unexposed. Animals were fed ad libitum and their growth and weight gain compared with non-exposed controls. At the end of the trial, blood samples were analysed for vitamin D3 metabolites. The concentration of the vitamin D3 metabolite, 25(OH)D3, was higher in UVb exposed animals (61 ± 20 vs. 38 ± 8 nmol/L), confirming cutaneous synthesis with UVb exposure. Growth and weight gain were similar in both groups, and this, together with the absence of clinical symptoms, suggests that dietary vitamin D3 alone can meet the vitamin D requirements for growth of this nocturnal gecko, during the first six months of life. It remains to be investigated whether the higher vitamin D metabolite levels holds other health benefits for this species, such as improved bone density or immune response.

Uptake of Cadmium, Lead and Arsenic by Tenebrio molitor and Hermetia illucens from Contaminated Substrates.

Insects have potential as a novel source of protein in feed and food production in Europe, provided they can be used safely. To date, limited information is available on the safety of insects, and toxic elements are one of the potential hazards of concern. Therefore, we aimed to investigate the potential accumulation of cadmium, lead and arsenic in larvae of two insect species, Tenebrio molitor (yellow mealworm) and Hermetia illucens (black soldier fly), which seem to hold potential as a source of food or feed. An experiment was designed with 14 treatments, each in triplicate, per insect species. Twelve treatments used feed that was spiked with cadmium, lead or arsenic at 0.5, 1 and 2 times the respective maximum allowable levels (ML) in complete feed, as established by the European Commission (EC). Two of the 14 treatments consisted of controls, using non-spiked feed. All insects per container (replicate) were harvested when the first larva in that container had completed its larval stage. Development time, survival rates and fresh weights were similar over all treatments, except for development time and total live weight of the half of the maximum limit treatment for cadmium of the black soldier fly. Bioaccumulation (bioaccumulation factor > 1) was seen in all treatments (including two controls) for lead and cadmium in black soldier fly larvae, and for the three arsenic treatments in the yellow mealworm larvae. In the three cadmium treatments, concentrations of cadmium in black soldier fly larvae are higher than the current EC maximum limit for feed materials. The same was seen for the 1.0 and 2.0 ML treatments of arsenic in the yellow mealworm larvae. From this study, it can be concluded that if insects are used as feed materials, the maximum limits of these elements in complete feed should be revised per insect species.