D3357: Honey bees do not form an aversive memory to sweet non-nutritious sugars

Honey bees possess taste receptors enabling them to detect sugar in nectar, yet not all sweet sugars are nutritious. Fruit flies exhibit a learned aversion to sweet but non-nutritional foods, known as caloric frustration memory, reflecting their ability to determine food suitability. In contrast, initial studies suggest honey bees (Apis mellifera) cannot differentiate taste from caloric content. To explore if honey bees can form caloric frustration memory, we utilized olfactory associative conditioning. We established L-glucose as an appetitive but non-nutritious sugar, contrasting with its isomer, D-glucose, which is both appetitive and nutritious. Bees were conditioned to associate an odor with either L- or D-glucose for 12 trials, followed by tests of short-, medium-, and long-term memory. Bees rewarded with L-glucose exhibited lower acquisition and reduced long-term memory compared to those rewarded with D-glucose. Previous work has established that during differential conditioning, bees cannot differentiate between an odor associated with appetitive reward containing malaise-causing compounds and an odor associated with an appetitive reward alone due to post-ingestive feedback signaling malaise. To determine if the drop in acquisition with L-glucose was due to malaise, we used differential conditioning. During conditioning, odor A paired with D-glucose and odor B with L-glucose resulted in lower responses to odor B, indicating L-glucose did not induce malaise. These results suggest that, unlike fruit flies, honey bees do not exhibit caloric frustration memory, indicating no negative signal is associated with the non-nutritious sugar.