Entomological Society of America
On-Demand 10-Minute Session
Available Wednesday, November 11, 2020
Click HERE and search for ‘Dodge’ to access the session on November 11th
Not just cold: Evidence of metabolic suppression during diapause in the bumble bee (Bombus impatiens)
Bumble bees have an annual cycle in which colonies produce males and new queens in fall. Workers and males die, but mated queens seek underground sites to overwinter, emerging in spring to found new colonies. Successful overwintering of queens is therefore critical for population growth and also relevant for commercial rearing of these important pollinators. These contexts have motivated substantial research on diapause initiation and termination cues, and on the effects of overwintering conditions on energy usage and survival. To our knowledge, however, no study has demonstrated that laboratory conditions purported to induce diapause in bumble bees result in metabolic suppression, the key indicator of diapause. Usually, queens are cooled to between 2 and 6 °C, then held there under the assumption that they are in diapause. Yet, bumble bees are ectothermic at cold temperatures, so it is unclear if bees in these conditions are simply cold or have further suppressed metabolism for diapause. We evaluated whether lab temperature manipulations could induce metabolic suppression in Bombus impatiens, confirming diapause initiation. Mated and unmated queens, subjected to a week-long temperature ramp from 22°C to 2°C, followed by holding at 2-4 °C for six weeks, showed pronounced metabolic suppression. Preliminary analyses reveal metabolic rates several fold lower than after rewarming, or after dropping directly to 4 °C. This suggests queen bumble bees will enter diapause (as indicated by metabolic suppression) in response to laboratory temperature cues, facilitating ongoing studies of the overwintering physiology of these crucial pollinators.
Presenting Author: D. M. Shayne Dodge
Co-Authors: Megan K. Dillon, Michael E. Dillon, PhD