ARS | Publication request: The effects of extended diapause duration on the metabolic rate and critical PO2 of the leafcutting bee, Megachilee rotundata

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 5, 2011
Publication Date: January 3, 2012
Citation: Bennett, M.M., Petersen, K.M., Yocum, G.D., Rinehart, J.P., Greenlee, K.J. 2012. The effects of extended diapause duration on the metabolic rate and critical PO2 of the leafcutting bee, Megachilee rotundata [abstract]. Society for Integrative and Comparative Biology. p. 69.

Technical Abstract: The Alfalfa leafcutting bee, Megachile rotundata F. (Hymenoptera: Megachilidae), is a solitary, cavity-nesting bee. Most individuals enter diapause at the end of summer and overwinter as prepupae. However, some individuals avoid diapause and complete their life cycle in the summer. Furthermore, some bees can survive artificially imposed diapause periods of varying length. Previous studies have shown that high temperature pulses during the overwintering period improved survival of adult bees. To determine whether lengthening the diapause period has an observable effect on the bees’ adult physiological phenotype, we measured resting and flight metabolic rates. We compared bees that had been maintained one year (simulating normal diapauses) to bees that had been maintained for two years. We used flow-through respirometry to measure resting and tethered flight metabolic rates. There was no significant difference in flight metabolic rate between the two groups, and flight metabolic rates were 20-fold higher than resting CO2 emission rate. To determine the critical PO2 (Pc) bees were exposed to decreasing levels of O2 for ten minutes each, and CO2 emission was recorded. Pc was similar between bees that had been stored for 1 or 2 years. Both groups of bees were very tolerant of hypoxia with a Pc between 3 and 5%. Increasing the diapause period by one year resulted in no significant difference in the bees’ Pc.