Oral Presentation 8th Venoms to Drugs 2023

Exploring sublethal effects of insecticides on contextual memory of insects (#50)

Volker Herzig 1 2 , Yachen Wang 1 2 , Shaodong Guo 1 2 , Tomer Ventura 1 2
  1. University of the Sunshine Coast, Sippy Downs, QLD, Australia
  2. Centre for Bioinnovation, University of the Sunshine Coast, Sippy Downs, QLD, Australia

Many commercial insecticides like the infamous neonicotinoids not only target pest but also beneficial insect species, including important pollinators like honeybees1. Besides apparent toxic effects such as locomotor impairment or death, sublethal doses of insecticides can induce less obvious effects on insect memory2,3. Contextual cues like the shape and colour of flowers, and their location in respect to the hive help guiding honeybees to their nectar source and impaired development or retrieval of these contextual memories could therefore reduce the bee's abilities in acquiring sufficient food. To study contextual memory in insects, we used the conditioned place preference (CPP) paradigm in fruit flies (Drosophila melanogaster) as a model organism.

The CPP paradigm is based on classical Pavlovian conditioning, in which a neutral stimulus (e.g. ringing of a bell) gets associated with an unconditioned stimulus (e.g. food) that leads to an unconditioned response (e.g. salivation in a dog)4. After repeated associations the neutral stimulus will become the conditioned stimulus that is sufficient to elicit the conditioned response (i.e. salivation) in the absence of the unconditioned stimulus. In our Drosophila CPP experiments, the environmental context was used as the neutral stimulus and sucrose solution was used as the unconditioned stimulus. We found the flies spent significantly more time in the sucrose-associated than in the water-associated chamber. We then employed Drosophila that developed sucrose CPP to test whether sublethal doses of commercial insecticides have any effect on the retrieval/expression of the contextual memory.

Interestingly, repeated associations with quinine resulted in significant conditioned place aversion (CPA), i.e. the flies spent significantly less time in the quinine-associated than in the water-associated chamber. Aversive behaviour could be an indication of discomfort or pain, and we therefore propose the CPA paradigm in fruit flies as a means of examining the aversive potential of defensive venom toxins.

  1. 1 Pisa, L. W. et al. Effects of neonicotinoids and fipronil on non-target invertebrates. Environ Sci Pollut Res Int 22, 68-102, doi:10.1007/s11356-014-3471-x (2015).
  2. 2 Cartereau, A. et al. Impairments in learning and memory performances associated with nicotinic receptor expression in the honeybee Apis mellifera after exposure to a sublethal dose of sulfoxaflor. PLoS One 17, e0272514, doi:10.1371/journal.pone.0272514 (2022).
  3. 3 Rosa, M. E. et al. Fipronil affects cockroach behavior and olfactory memory. J Exp Biol 226, doi:10.1242/jeb.245239 (2023).
  4. 4 Tzschentke, T. M. Measuring reward with the conditioned place preference paradigm: a comprehensive review of drug effects, recent progress and new issues. Prog Neurobiol 56, 613-672, doi:10.1016/s0301-0082(98)00060-4 (1998).