Long-term after-effects of cold exposure in adult Alphitobius diaperinus (Tenebrionidae): the need to link survival ability with subsequent reproductive success.
Résumé
1. The effects of cold acclimation and cold exposure on the survival and reproductive capabilities of Alphitobius diaperinus (Tenebrionidae) adult beetles are examined. 2. First, the impact of temperature on survival duration was assessed by placing beetles in a range of cool temperature treatments. Second, the importance of acclimation duration was assessed. Third, the impact of thermal stress on subsequent reproductive ability was examined for beetles that had no previous cold exposure, and for beetles that had been subjected to previous cold exposure (i.e. acclimated) at various conditions, including fluctuating temperatures. 3. In all groups, the number of recorded survivors was strongly impacted by recovery period duration (i.e. 2 vs. 10 days). Survival of non-acclimated and 3-day acclimated beetles, expressed as lethal time for 50% of the samples, was reduced significantly when the insects were re-assessed for survival at 10 days after being returned to optimal growth conditions (7.9 ± 0.4 vs. 5.1 ± 0.6 days and 8.8 ± 0.5 vs. 6.8 ± 0.6 days, respectively). 4. Insects that had been subject to cold acclimation expressed better subsequent reproduction success than non-acclimated beetles. This beneficial impact increased when the acclimation period was prolonged, but some longer acclimation periods had no significant impact on survival. 5. Our results indicate that cold exposure has the capacity to irreversibly damage the reproductive system and that insect survival depends on the duration of the recovery period. Both the survival ability and subsequent reproductive output have to be examined to objectively determine insect cold resistance.