Sex dimorphic adaptive responses against Azadirachtin toxicity in gut tissues of Spathosternum prasiniferum prasiniferum (Orthoptera; Acridoidea)

Acridids (short-horned-grasshopper) are distributed largely in the agricultural-field, grass-lands, and forests. It may act as a dependable bio-indicator species in response to ecological-stress. Among the acridids found in West Bengal, Spathosternum prasiniferum prasiniferum (Walker, 1871) are multivoltine in nature and were considered for the present study. Azadirachtin is a tetranortri terpenoids present in neem tree (Azadirachta indica), which develops antifeedancy/ growth-regulation/ fecundity-suppression/ sterilization/ oviposition/ repellence and deformity in insect via oxidative stress by the production of free radicals and causes their death. Antioxidants protect insects by scavenging free radicals. This study explored Azadirachtin toxicity on food-indices/biochemical/physiological influences on mid-gut of Spathosternum prasiniferum prasiniferum. Commercially available Azadirachtin was applied (1–20 ppm) on S. pr. prasiniferum for in vivo/in vitro experiment, where gut-tissues were analysed to determine oxidative-stress-markers (ALP/MDA/NPSH/AChE), antioxidant-markers (SOD/CAT/GPx). Food-weight/insect-weight/excreta-weight were recorded before/after the experiment to evaluate the consumption-index(CI), approximate-digestibility(AD), efficiency of conversion of digested-food(ECD) and efficiency of conversion of ingested-food(ECI). Nutrient metabolizing-enzymes (cellulase/amylase) were screened. Azadirachtin (>7 ppm) decreased ECD and restricted food-consumption that increased insect-mortality (50–80%). The gut MDA significantly increased with an impairment of soluble-thiols. The antioxidant-enzymes were variably impaired resulting in tissue-damages more in male than female. Finally, Azadirachtin influenced nutrient-metabolizing-enzymes and antioxidant-enzymes indicating these parameters to be good stress-markers. This finding might be extrapolated for further evaluation of the ecological impact of Azadirachtin on the food chain/web in a composite-ecosystem.