Olfactory Strategies in the Defensive Behaviour of Insects
2022-05-18, Kannan, Kavitha, Galizia, C. Giovanni, Nouvian, Morgane
Most animals must defend themselves in order to survive. Defensive behaviour includes detecting predators or intruders, avoiding them by staying low-key or escaping or deterring them away by means of aggressive behaviour, i.e., attacking them. Responses vary across insect species, ranging from individual responses to coordinated group attacks in group-living species. Among different modalities of sensory perception, insects predominantly use the sense of smell to detect predators, intruders, and other threats. Furthermore, social insects, such as honeybees and ants, communicate about danger by means of alarm pheromones. In this review, we focus on how olfaction is put to use by insects in defensive behaviour. We review the knowledge of how chemical signals such as the alarm pheromone are processed in the insect brain. We further discuss future studies for understanding defensive behaviour and the role of olfaction.
Complexity and plasticity in honey bee phototactic behaviour
2020-05-12, Nouvian, Morgane, Galizia, C. Giovanni
The ability to move towards or away from a light source, namely phototaxis, is essential for a number of species to find the right environmental niche and may have driven the appearance of simple visual systems. In this study we ask if the later evolution of more complex visual systems was accompanied by a sophistication of phototactic behaviour. The honey bee is an ideal model organism to tackle this question, as it has an elaborate visual system, demonstrates exquisite abilities for visual learning and performs phototaxis. Our data suggest that in this insect, phototaxis has wavelength specific properties and is a highly dynamical response including multiple decision steps. In addition, we show that previous experience with a light (through exposure or classical aversive conditioning) modulates the phototactic response. This plasticity is dependent on the wavelength used, with blue being more labile than green or ultraviolet. Wavelength, intensity and past experience are integrated into an overall valence for each light that determines phototactic behaviour in honey bees. Thus, our results support the idea that complex visual systems allow sophisticated phototaxis. Future studies could take advantage of these findings to better understand the neuronal circuits underlying this processing of the visual information.
Aversive training of honey bees in an automated Y-maze
2019-06-04, Nouvian, Morgane, Galizia, C. Giovanni
Honeybees have remarkable learning abilities given their small brains, and have thus been established as a powerful model organism for the study of learning and memory. Most of our current knowledge is based on appetitive paradigms, in which a previously neutral stimulus (e.g. a visual, olfactory, or tactile stimulus) is paired with a reward. Here we present a novel apparatus, the yAPIS, for aversive training of walking honey bees. This system consists in 3 arms of equal length and at 120° from each other. Within each arm, colored lights (λ=375, 465 or 520 nm) or odors (here limonene or linalool) can be delivered to provide conditioned stimuli (CS). A metal grid placed on the floor and roof delivers the punishment in the form of mild electric shocks (unconditioned stimulus, US). Our training protocol followed a fully classical procedure, in which the bee was exposed sequentially to a CS paired with shocks (CS+) and to another CS not punished (CS-). Learning performance was measured during a second phase, which took advantage of the Y-shape of the apparatus and of real-time tracking to present the bee with a choice situation, e.g. between the CS+ and the CS-. Bees reliably chose the CS- over the CS+ after only a few training trials with either colors or odors, and retained this memory for at least a day, except for the shorter wavelength (λ=375nm) that produced mixed results. This behavior was largely the result of the bees avoiding the CS+, as no evidence was found for attraction to the CS-. Interestingly, trained bees initially placed in the CS+ spontaneously escaped to a CS- arm if given the opportunity, even though they could never do so during the training. Finally, honey bees trained with compound stimuli (color + odor) later avoided either components of the CS+. Thus, the yAPIS is a fast, versatile and high-throughput way to train honey bees in aversive paradigms. It also opens the door for controlled laboratory experiments investigating bimodal integration and learning, a field that remains in its infancy.