Appetitive but not aversive olfactory conditioning modifies antennal movements in honeybees

Abstract

In honeybees, two olfactory conditioning protocols allow the study of appetitive and aversive Pavlovian associations. Appetitive conditioning of the proboscis extension response (PER) involves associating an odor, the conditioned stimulus (CS) with a sucrose solution, the unconditioned stimulus (US). Conversely, aversive conditioning of the sting extension response (SER) involves associating the odor CS with an electric or thermal shock US. Each protocol is based on the measure of a different behavioral response (proboscis versus sting) and both only provide binary responses (extension or not of the proboscis or sting). These limitations render the measure of the acquired valence of an odor CS difficult without testing the animals in a freely moving situation. Here, we studied the effects of both olfactory conditioning protocols on the movements of the antennae, which are crucial sensory organs for bees. As bees' antennae are highly mobile, we asked whether their movements in response to an odorant change following appetitive or aversive conditioning and if so, do odor-evoked antennal movements contain information about the acquired valence of the CS? We implemented a tracking system for harnessed bees' antennal movements based on a motion capture principle at a high frequency rate. We observed that differential appetitive conditioning had a strong effect on antennal movements. Bees responded to the reinforced odorant with a marked forward motion of the antennae and a strong velocity increase. Conversely, differential aversive conditioning had no associative effect on antennal movements. Rather than revealing the acquired valence of an odorant, antennal movements may represent a novel conditioned response taking place during appetitive conditioning and may provide a possible advantage to bees when foraging in natural situations.

SwarmSight: Real-time Tracking of Insect Antenna Movements and Proboscis Extension Reflex Using a Common Preparation and Conventional Hardware

“…The software requires that the head of the animal is fixed in place and is not moving during the video. This is similar to the preparations of previous work 48 49 50 51 . It is possible to modify the software to allow automatic detection of head rotations, however, this would consume additional processing time and introduce a new source of error.…”

“…Special equipment and preparation can be used to reduce the need for complex software. For example, one setup used a high-speed camera and painted the tips of the antennae to track the antenna movement 48 . Users can also be asked to select key-frames of videos to assist the software in detecting the antenna and proboscis location 49 .…”

Sickness Behavior in Honey Bees

“…Using antennal scanning of objects, bees can discriminate between shapes, textures, and sizes and can associate them with rewards (Kevan and Lane, 1985 ; Erber et al, 1998 ; Scheiner et al, 2001 ). Moreover, the speed and directionality of the antennal movements change in front of appetitively conditioned odors (Cholé et al, 2015 ). Therefore, antennal movements are a good indicator of exploratory behavior.…”

Heat Perception and Aversive Learning in Honey Bees: Putative Involvement of the Thermal/Chemical Sensor AmHsTRPA

“…We then asked whether HsTRPA is necessary for bees to detect heat and respond with a sting extension. We focused here on SER triggered by thermal stimulation on the mouthparts, the US commonly used for aversive thermal conditioning (Junca et al, 2014 ; Cholé et al, 2015 ). Two chemical inhibitors of HsTRPA have been identified in vitro (Kohno et al, 2010 ), menthol and ruthenium red (RuR).…”

“…To this end, we evaluated the effects of known HsTRPA activators and inhibitors. We focused on the SER triggered by thermal stimulation on the mouthparts, as this is the US commonly used for aversive thermal conditioning (Junca et al, 2014 ; Cholé et al, 2015 ).…”