Soil characteristics and nutritional traits of Mactrotermes natalensis (Isoptera: Macrotermitinae) as indicators of nutritional quality in Zimbabwe

Macrotermes natalensis is a widely consumed edible termite species that inhabits termitaria of different soil colours in southern Africa. However, there is paucity of data regarding the relationship between termitaria soil properties, nutritional composition and safety for edible soldier termites. We hypothesised that soil properties viz. metal composition, and colour are positively correlated to mineral composition, bioactive compounds and level of contamination by heavy metals in soldier termites. Replicated insects samples were collected from termitaria of different soil colour types from Bikita district, Zimbabwe. Soil and insect mineral composition were determined using standard methods. Antioxidant properties of methanol insect extracts were estimated using the DPPH test. A cluster analysis was performed to relate soil colour to soil and insect minerals compositions and DPPH. Soil Zn and Cu significantly varied ( P < 0.05) with respect to soil colour. Termitaria with grey colour were associated with higher content of Zn in the soil (23.5 mg/kg) compared to other soil colours. Higher ( P < 0.05) Pb content (4.48 mg/kg) was detected in termites from yellowish-brown soil colour compared to dark-grey, grey, brown and light-gray (2.45, 1.45, 0.5, 0.49 mg/kg, respectively). The content of Cu and Zn in soil were significantly positively correlated to Cu and Zn in insects and inversely correlated to Pb detected in insects. Percentage DPPH (overall >50%) was independent of soil colour, soil and insect mineral composition. There is a possible risk of Pb poisoning associated with consumption of soldier Macrotermes natalensis irrespective of termitaria soil colour; however, the risk is more pronounced in insects gathered from yellowish-brown soils.