Oxygen Consumption as a Measurement of Diapause Termination in the Korean Native Bumblebee, Bombus ignitus

Abstract

Bumblebees are a commercially important pollinator of both agricultural crops and natural plants, particularly tomato, which require huge, buzzing pollinators. The artificial rearing of these bees is increasing to meet the growing demand, and breaking diapause is a critical element in this process. As the pre-diapause Bombus ignitus queen has a higher metabolic rate than that of the post-diapause B. ignitus queen, we hypothesized that there would be a difference in the oxygen consumption of the queen before and after wintering. Therefore, we measured the rate of oxygen consumption of B. ignitus queens to create a barometer for evaluating diapause termination. The O2 uptake of B. ignitus queens was 39.0 μL/㎎ wt./min just after emergence and increased rapidly from 186.3 μL/㎎ wt./min at 6 h after emergence to 354.2 μL/㎎ wt./min one day after emergence. The rates of oxygen uptake of the queens during the first 6 days after emergence raised from 354.8 μL/㎎ wt./min at one day to a maximum level of 494.7 μL/㎎ wt./min in the 5-day-old queens, which corresponds to 3.4-fold increase from that just after emergence. When evaluating the oxygen consumption of queens that are presumed to have completed hibernation in the nature, we found that the oxygen consumption was 265.1~306.2 μL/㎎ wt./min, similar to that of the queen bees in this study the first day after hibernation. Therefore, we defined the standard for termination of dormancy of B. ignitus queen bees in the range of 250~300 μL/㎎ wt./min. Furthermore, our results indicate that oxygen consumption can provide important information for the indoor rearing of B. ignitus. During the wintering period, the oxygen consumption of the B. ignitus queen bees clearly increased as time passed, and the oxygen consumption value of the queen bees sampled at the 4th month of hibernation was 195.7 μL/㎎ wt./min, which was close to the oxygen consumption value at the end of hibernation. The queen bees, which were stored at 2.5℃ for artificial wintering, showed the highest oxygen consumption value after the end of hibernation. Based on these findings, we concluded that oxygen consumption of the bumblebee can provide rare insight for artificially raising B. ignitus as a barometer for measuring diapause termination in this species.