Among the various “omics” approaches that can be used in toxicology, volatolomics is in full development. A volatolomic study was carried out on soil bacteria to validate the proof of concept, and this approach was implemented in a new model organism: the honeybee Apis mellifera. Emerging bees raised in the laboratory in pain-type cages were used. Volatolomics analysis was performed on cuticles, fat bodies, and adhering tissues (abdomens without the digestive tract), after 14 and 21 days of chronic exposure to 0.5 and 1 µg/L of fipronil, corresponding to sublethal doses. The VOCs analysis was processed using an HS-SPME/GC-MS method. A total of 281 features were extracted and tentatively identified. No significant effect of fipronil on the volatolome could be observed after 14 days of chronic exposure. Mainly after 21 days of exposure, a volatolome deviation appeared. The study of this deviation highlighted 11 VOCs whose signal abundances evolved during the experiment. Interestingly, the volatolomics approach revealed a VOC (2,6-dimethylcyclohexanol) that could act on GABA receptor activity (the fipronil target) and VOCs associated with semiochemical activities (pheromones, repellent agents, and compounds related to the Nasonov gland) leading to a potential impact on bee behavior.

Fipronil, a non-competitive antagonist of γ-aminobutyric acid receptors (GABA-Rs), inhibits the flow of chloride ions in the nerve cells, leading to the insect death. In a previous work, the volatolome of bees chronically exposed to this insecticide (0.5 and 1 μ g/L) was analyzed and characterize the Apis mellifera metabolic responses. Two Volatile Organic Compounds or VOCs (1-octen-3-ol and 2,6-dimethylcyclohexanol) produced by bee were highlighted. We assumed that these VOCs could act as modulators of the GABA-R to counteract the effect of fipronil. The toxicity of these VOCs was tested on emerging bees for concentrations ranging from 0 to 3.4 μ g/L. Survival and the sucrose consumption were recorded during 21 days of chronic exposure. 1-octen-3-ol and 2,6-dimethylcyclohexanol did not significantly affect the proportion of survival at the end of the experiment, whatever their concentration. 1-octen-3-ol (0.5, 1, 1.7 and 3.4 μ g/L) was chosen to assess its effect in the case of co-exposure with fipronil (0.5 and 1 μ g/L). A beneficial effect on survival at 21 days was observed with an average improvement in survival rate for the co-exposed groups. This positive effect was not related to the VOC concentration and could be a direct effect (interaction with GABA-R) or a hormetic effect (global improvement of bee fitness).