The reluctant visitor: an alkaloid in toxic nectar can reduce olfactory learning and memory in Asian honey bees

The nectar of the thunder god vine, Tripterygium hypoglaucum, contains a terpenoid, triptolide (TRP), that is toxic to the sympatric Asian honey bee, Apis cerana. However, these bees will forage on, recruit for, and pollinate this plant during a seasonal dearth of preferred food sources. Olfactory learning plays a key role in forager constancy and pollination, and we therefore tested the effects of acute and chronic TRP feeding on forager olfactory learning, using proboscis extension reflex conditioning. At a concentration of 0.5ug TRP/ml, within the natural range, there were no learning effects. However, memory retention (1 h after the last learning trial) significantly decreased by 56% following acute consumption of 0.5 ug TRP/ml. Chronic exposure did not alter learning or memory, except at high concentrations (5 and 10 ug TRP/ml) that are likely not biologically relevant. Natural TRP concentrations in nectar should therefore not significantly harm plant pollination. Long term exposur...