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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Insect Genetics and Biochemistry Research » Research » Publications at this Location » Publication #241956
Title: Effect of Temperature Regime on Diapause Intensity in an Adult-Wintering Hymenopteran with Obligate Diapause

Author
item SGOLASTRA, FABIO - Universita Di Bologna
item BOSCH, JORDI - University Of Barcelona
item MOLOWNY, ROBERTO - University Of Barcelona
item MAINI, STEFANO - Universita Di Bologna
item Kemp, William - Bill

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2009
Publication Date: 2/1/2010
Citation: Sgolastra, F., Bosch, J., Molowny, R., Maini, S., Kemp, W.P. 2010. Effect of Temperature Regime on Diapause Intensity in an Adult-Wintering Hymenopteran with Obligate Diapause. Journal of Insect Physiology. 56(2):185-194.

Interpretive Summary: Osmia lignaria is a solitary bee that is being developed as an alternative pollinator of tree fruit crops in North America. In this study we studied the effect of wintering temperature on diapause maintenance and termination in this species, which winters as a cocooned adult in northerly latitudes. We measured respiration rates and weight loss in individuals exposed to various wintering temperatures (0, 4, 7, 22°C, outdoors) and durations (28, 84, 140, 196, 252 days). Adults lower their respiration rates to ~ 0.1 ml/g*h within one month after moulting to the adult stage. Individual bees not subjected to low temperatures cues, normally encountered under natural conditions, maintain low respiration rates, but loose weight rapidly and die by mid-winter. In wintered adults, two phases can be distinguished. First, respiration rates (measured at 22°C) undergo a rapid increase and reach a plateau. This phase is similar in bees wintered at 0, 4 and 7°C. Then, respiration rates undergo an exponential increase, which is more pronounced at the warmer temperatures. Adult bees whose CO2 production has reached 0.45 ml/g*h emerge promptly when exposed to 20°C, indicating diapause completion. Individuals wintered for short periods do not reach such respiration levels. When exposed to 20°C these individuals lower their metabolic rate, and their emergence time is extended. In individuals wintered under natural ambient conditions, respiration rates remain low throughout the winter and increase rapidly in April, as soon as temperatures reach ~20°C. The results of these investigations will contribute to the development of standardized management protocols for the commercial-scale mass-rearing of O. lignaria populations.

Technical Abstract: Osmia lignaria is a solitary bee that overwinters as a fully-eclosed, cocooned, unfed adult. Our objective is to understand the effect of wintering temperature on diapause maintenance and termination in this species. We measured respiration rates and weight loss in individuals exposed to various wintering temperatures (0, 4, 7, 22°C, outdoors) and durations (28, 84, 140, 196, 252 days). Adults lower their respiration rates to ~ 0.1 ml/g*h within one month after adult eclosion. Non-chilled individuals maintain low respiration rates, but loose weight rapidly and die by mid-winter. In wintered adults, two phases can be distinguished. First, respiration rates (measured at 22°C) undergo a rapid increase and reach a plateau. This phase is similar in bees wintered at 0, 4 and 7°C. Then, respiration rates undergo an exponential increase, which is more pronounced at the warmer temperatures. Composite exponential functions provide a good fit to the observed respiration patterns. Adults whose CO2 production have reached 0.45 ml/g*h emerge promptly when exposed to 20°C, indicating diapause completion. Individuals wintered for short periods do not reach such respiration levels. When exposed to 20°C these individuals lower their metabolic rate, and their emergence time is extended. The relationship between respiration rates and emergence time follows a negative exponential function. In individuals wintered outdoors, respiration rates remain low throughout the winter and they skyrocket in April, as soon as temperatures reach ~20°C.