The nectar of the thunder god vine, Tripterygium hypoglaucum, contains a terpenoid, triptolide (TRP), that may be toxic to the sympatric Asian honey bee, Apis cerana. Aisan honey bee foragers have good olfactory learning, but no studies have examined how TRP may alter their learning and memory.
Prof. TAN Ken and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to test whether feeding on artificial nectar with TRP would impair forager olfactory learning and memory retention. They used a wide range of TRP concentrations and tested the effects of TRP consumption on bees exposed to a single dose (acute exposure) or over multiple days (chronic exposure).
They found that triptolide (TRP) significantly impaired olfactory learning at a concentration(0.5 µg/ml) found in the honey of bees that collected nectar from T. hypoglaucum inflorescences and at higher concentrations that may be found in T. hypoglaucum nectar.
The researchers examined the effects of both acute and chronic exposure and found a higher overall effect in bees chronically fed TRP. However, the strongest memory effect occurred following acute exposure: memory retention decreased by 56% for the 0.5 µg/ml dose as compared to the control 1 hour after the last learning reinforcement trial.
In the chronic exposure experiment, learning and memory retention were only impaired at the higher doses of 5 and 10 µg/ml. Interestingly, TRP consumption slightly but significantly increased survival over 7 days.
The results suggest that TRP alone may not account for increased mortality in bees fed T. hypoglaucum honey. TRP can reduce bee memory of a rewarded odor.
The study entitled “The reluctant visitor: an alkaloid in toxic nectar can reduce olfactory learning and memory in Asian honey bees” has been published online in Journal of Experimental Biology.
TAN Ken, Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China