Lethal and sublethal effects of imidacloprid, after chronic exposure, on the insect model Drosophila melanogaster

Neonicotinoids are subjected to vigilance because of environmental contaminations and deleterious effects on bees. Imidacloprid (IMI) is one of the most representative insecticides of this family. At chronic exposure, concentration-effect relationships are non linear. An insect model should allow a better description of this toxicity. We compared the lethal concentration 50% (LC50) of IMI for a Drosophila-field strain, after acute and chronic exposure. Relative to the acute LC50, the chronic LC50 was lowered by a factor of 29 for males (1.3 mM/45 µM), 52 for larvae (157 µM/3µM) and more than 172 for females (>3.1mM/18µM). Chronic exposure also revealed significant lethal and sublethal effects, at concentrations 3-5 orders of magnitude lower than the chronic LC50. Mean mortalities reached 28% (at 3.91 nM) and 27% (at 39.1 nM) for females and males, respectively. Fecundity decreased of 16% at 1.96 nM. Mating increased of 30% at 0.391 nM. The LOEC (Lowest Observed Effect Concentration: 0.391 nM) was 46000 times lower than the chronic LC50 for males; it was 115000 times lower than the chronic LC50 for females. This study illuminates effects that neonicotinoids can induce at very low concentrations. This is of particular interest for non-target insects and for insect dependent species.

Source: Gaël Charpentier , Fanny Louat , Jean-Marc Bonmatin , Patrice André Marchand , Fanny Vannier , Daniel Locker , and Martine Decoville. Lethal and sublethal effects of imidacloprid, after chronic exposure, on the insect model Drosophila melanogaster, Environ. Sci. Technol., Just Accepted Manuscript DOI: 10.1021/es405331c

Publication Date (Web): March 3, 2014
http://pubs.acs.org/doi/abs/10.1021/es405331c