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The importance of fluctuating thermal regimes for repairing chill injuries in the tropical beetle Alphitobius diaperinus (Coleoptera: Tenebrionidae) during exposure to low temperature

Renault, D., Nedved, O., Hervant, F., Vernon, P.
Physiological entomology 2004 v.29 no.2 pp. 139-145
Alphitobius diaperinus, cold tolerance, chilling injury, temperature, acclimation, mortality, supercooling point
In this study, the impact of acclimation (1 month at 15°C vs. breeding at 30°C) and fluctuating thermal regimes (daily transfers from low temperatures to various higher temperatures for 2 h) on the cold tolerance of the tropical beetle, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) was examined. Acclimation increased significantly the duration of survival (Lt50) at a constant 5°C (7.7 ± 0.3 days to 9.7 ± 0.5 days). Survival of acclimated and nonacclimated beetles increased slightly at alternating temperatures of 5°C/10°C or 5°C/15°C. When daily transfer to 20°C was applied, survival (Lt50) was improved markedly (nonacclimated: 15.5 ± 0.7 days, acclimated: 19.6± 0.6 days). The higher temperatures may allow progressive repair of injuries, and the effects of chilling may be repaired completely at 25 and 30°C, a phenomenon recorded here for the first time. It is estimated that the theoretical upper threshold of chill injury (Th) of nonacclimated beetles is 15.1°C whereas it is shifted down to 11.2°C in acclimated beetles, which might enable this temperature to allow effective repair of injury.