Meeting Abstract

P2.110  Thursday, Jan. 5  The effects of extended diapause duration on the metabolic rate and critical PO₂ of the alfalfa leafcutting bee, Megachilee rotundata BENNETT, M.M.*; PETERSEN, K; YOCUM, G; RINEHART, J; GREENLEE, K; North Dakota State University; Concordia College; United States Dept of Agriculture; United States Dept of Agriculture; North Dakota State University meghan.bennett@ndsu.edu

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 at 6C for 12 months (simulating normal diapauses) to bees that had been kept at 6°C for 24 months. 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(P_c) bees were exposed to decreasing levels of O₂ for ten minutes each, and CO₂ emission was recorded. P_c was similar between bees that had been stored for 12 or 24 months. Both groups of bees were very tolerant of hypoxia with a P_c between 3 and 5%. Increasing the diapause period by 12 months resulted in no significant difference in the bees’ P_c. Together these data suggest that diapause length has no affect on adult metabolism. Whether increasing diapause duration affects other parameters of adult physiology, such as foraging capacity or reproductive fitness remains unclear.