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VIII SIMPOSIO INTERNAZIONALE ICPBR HAZARDS
OF PESTICIDES TO BEES Metodologie dei test e studi sugli effetti dei pesticidi sulle api A tentative method to evaluate behavioural effects of pesticides on honey bees: the proboscis extension response Axel Decourtye (1), James Devillers (2), Sophie Cluzeau (3), Gilbert Maurin (3) and Minh-Hà Pham-Delègue (1) (1) Laboratoire
de Neurobiologie Comparée des Invertébrés, INRA,
BP 23, 91440 Bures-sur-Yvette, France Risk assessment of chemical pesticides on honey bees is based on a sequential scheme including laboratory, semi-field and field evaluation. These methods mainly take into account the survival of bees exposed to pesticides. Besides mortality, various aspects of the honey bees behaviour may be affected by sublethal doses of pesticides. Among the bees of a colony, foragers are the most likely to be exposed to chemicals. The foraging behaviour is known to rely on a conditioning process, floral cues being associated to the food, memorized and used for flower recognition during the following trips. The conditioning process occurring on the flower can be reproduced under laboratory conditions, using the olfactory conditioning of the proboscis extension response (PER), on restrained individuals. The classical odour conditioning of the PER is based on the temporal paired association of a conditioned stimulus (odour) and an unconditioned stimulus (sucrose solution). Bees can exhibit the PER as a conditioned response to the odour alone after even a single odour-sucrose solution presentation. This procedure allows standardised recordings of behavioural responses and provides information on learning and memory processes. The PER bioassay has been adapted to the screening of the effects of a range of chemicals at sublethal concentrations. It was applied to 15-day-old bees surviving a diet contaminated with pesticide over 11 days. This is an attempt to simulate what young hive bees could experiment when feeding on contaminated stored food, before becoming foragers. The PER procedure allowed to establish threshold concentrations above which a significant decrease in olfactory learning abilities is observed. The PER assay also enables comparative studies of responses to different chemical treatments (organochlorine, organophosphorus, pyrethroid, imidazole, phenylpyrazole, carbamylpyrazole). The laboratory
conditions can be considered as worst case conditions, which do not
reflect the natural conditions. Therefore, we were concerned about testing
the PER after more realistic exposure conditions in a standard crop
protection agronomic system. Bees foraging on treated and control crops
have shown differences in a PER assay under laboratory conditions. These
preliminary results indicate the possibility to subject the bees to
the PER assay after an exposure to chemical pesticides under agronomic
conditions.
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