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Impacts d’un biopesticide, l’azadirachtine, sur la physiologie et le comportement de Drosophila melanogaster : Reproduction, nutrition et propriétés aversives

Abstract : While the acute toxicity of xenobiotics on organisms is well known, long term effects of intermittent exposures are less studied. Here we examined the effects of a single larval exposure to a commercial antifeedant and insecticide Neem-Azal (containing 1% azadirachtin A), on Drosophila melanogaster. Two doses (LD25 : 0.28 µg, LD50 : 0.67 µg corresponding respectively to 25% and 50% cumulative mortality of immature stages) were used by topical application on early third instar larvae (L3). The possible adverse effects of this prior single exposure to azadirachtin experienced by the preceding generations were evaluated over three successive generations until full restoration of the studied parameters.The single pre-imaginal exposure of azadirachtin affects female fecundity by significantly reducing the number of eggs laid over two successive generations (P and F1). Full restoration of affected fecundity was noted in the second generation (F2). Larval treatment also affects oviposition choices, the surviving flies avoiding treated substrates more than control flies for all tested generations.Early exposure to azadirachtin also affects adult’s development by reducing the number of organisms, delay larval and pupal development ; male biased sex ratio and induced morphological alterations. This exposure significantly reduces adult’s survival during two successive generations. Moreover, azadirachtin was found to affect Drosophila adult’s locomotor reactivity by significantly decreased the geotactic positioning scores of adults of both sexes as compared to controls.Azadirachtin affects the amount of food intake by the flies and disrupts the chemosensory system of the adults by affecting their olfactory and gustatory choices. Results showed that previously treated flies (3rd instar larvae) showed an aversion to the biopesticide avoiding azadirachtin odor. The biopesticide also inhibited the proboscis extension response in the adults of both sexes with more marked effects in treated flies. The electrophysiological studies of gustatory response showed an increase of sensibility of gustatory sensilla to azadirachtin previously exposed flies confirming the more marked avoidance to this molecule.
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Submitted on : Thursday, January 27, 2022 - 7:07:09 PM
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Maroua Ferdenache. Impacts d’un biopesticide, l’azadirachtine, sur la physiologie et le comportement de Drosophila melanogaster : Reproduction, nutrition et propriétés aversives. Toxicologie. Université Paris-Saclay; Université Badji Mokhtar-Annaba, 2021. Français. ⟨NNT : 2021UPASB025⟩. ⟨tel-03546240⟩

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