Adult mortality and blood feeding behavioral effects of α-amyrin acetate, a novel bioactive compound on in vivo exposed females of Anopheles stephensi Liston (Diptera: Culicidae)

Abstract

The effect of α-amyrin acetate on mortality and blood feeding behavior in females of Anopheles stephensi was assessed by in vivo exposure on treated guinea pig skin. In vivo exposure to α-amyrin acetate caused mosquito knock down in the form of rapidly and normally reversible paralysis and the subsequent record at the end of a 24 h, revealed mortality rates of females increased from 0.0% (Control) to 76.9% at 1.6% α-amyrin acetate, the highest concentration which implies the contact toxicity of the α-amyrin acetate received through the sensitive parts of test species. The mean probing time responses significantly increased (P < 0.05) from 5.3 s (Control) to 22.9 s at 1.6% α-amyrin acetate. The blood feeding rates and the mean engorgement times were significantly shorter when compared to the control. The mean blood feeding rates of exposed females decreased from 91.7% (control) to 41.5% at 0.8% α-amyrin acetate concentrations, the mean engorgement time also decreased from 278.6 s (Control) to 158.7 s at 0.8% α-amyrin acetate concentrations. Mean blood feeding rates and mean engorgement time were statistically significant (P < 0.05) from that of control. The mean fecundity levels significantly reduced from 96.2 (Control) to 65.95%. The shortened mean engorgement time and smaller blood meal size have played a more important role in decline of fecundity. In vivo exposure to α-amyrin acetate caused increased mean probing time, decreased blood engorgement time and feeding rate and declined fecundity which reduce the overall survival and reproductive capacity of the malaria vector A. stephensi.