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First published online June 16, 2005
Journal of Experimental Biology 208, 2615-2620 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01685
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Low temperature acclimated populations of the grain aphid Sitobion avenae retain ability to rapidly cold harden with enhanced fitness

S. J. Powell* and J. S. Bale

School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

* Author for correspondence (e-mail: sjp822{at}bham.ac.uk)

Accepted 18 April 2005

In contrast to previous studies of rapid cold-hardening (RCH), which have investigated the responses of insects maintained under `summer conditions' (20° to 25°C), this study focuses on the ability of low-temperature acclimated insects to undergo RCH. When the grain aphid Sitobion avenae Fabricus was low-temperature acclimated by rearing for three generations at 10°C, the discriminating temperatures (temperature that results in approximately 20% survival after direct transfer from the rearing temperature to a sub-zero temperature for a period of 3 h), of first instar nymphs and adult aphids were –11.5° and –12°C, respectively. Maximum rapid cold-hardening was induced by cooling aphids at 0°C for 2 h (nymphs) or 30 min (adults), resulting in survival at the respective discriminating temperatures increasing from 26% to 96% (nymphs) and 22% to 70% (adults). Cooling from 10° to 0°C at 1°, 0.1° and 0.05°C min-1 significantly increased survival of nymphs at the discriminating temperature, but not of adults. There were no `ecological costs' associated with rapid cold-hardening at 0°C, or with exposure of rapidly cold-hardened aphids to the discriminating temperatures; fecundity and longevity, in both nymphs and adults were either similar to control aphids or significantly increased. The study demonstrates that rapid cold-hardening ability is retained in aphids that have already undergone cold-acclimation, as would be the case in overwintering aphids. Both rapid cold-hardening and subsequent exposure at previously lethal temperatures can enhance fitness in surviving individuals.

Key words: rapid cold-hardening, seasonal acclimation, aphid, Sitobion avenae, fitness


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© The Company of Biologists Ltd 2005