Effects of Pergularia tomentosa active fraction on the oogenesis of the desert locust, Schistocerca gregaria: ovarian biochemical composition, and effects on the ecdysteroid pathway

Abstract

Fractionation of the methanolic extract of Pergularia tomentosa, using column chromatography, resulted in the separation of 10 fractions and only the active one (that gave mortality >70%) was kept and denoted the active fraction (AFPt). Adult female Schistocerca gregaria were treated with two concentrations of AFPt, 0.24% and 0.96%, to investigate the effect on the female reproductive potential. Both concentrations of AFPt significantly increased the duration between adult emergence and first oviposition, as well as affected fecundity and fertility. Furthermore, the effects of AFPt on vitellogenesis and ecdysteroid titres were examined. Biochemical analyses revealed a significant decrease in protein, lipid and carbohydrate contents in ovaries. This study also showed that AFPt induced a significant decrease in the ovarian ecdysteroids levels, as well as the haemolymph ecdysteroid titres. The transcript levels of the ecdysteroid synthesis enzymes Spook and Shadow were significantly decreased when treated with the highest concentration of AFPt, while transcript levels of the ecdysteroid synthesis enzymes Phantom and Disembodied increased significantly in animals treated with AFPt. Treatment with AFPt also resulted in a significantly higher transcript level of both the ecdysone receptor (EcR) and its partner ultraspiracle/retinoid‐X‐receptor (USP/RXR).