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Keywords:

  • acclimation;
  • cold resistance;
  • desiccation resistance;
  • fitness cost;
  • hardening;
  • heat resistance;
  • longevity;
  • starvation resistance

Summary

1. Acclimation or hardening to one stress in arthropods can lead to a plastic response, which confers increased resistance to other stresses. Such cross-resistance may indicate shared physiological resistance mechanisms and a possibility of joint evolution for resistance traits.

2. In this study, we tested for cross-resistance using Drosophila melanogaster as a model system. Adult females were assayed for resistance to cold, heat, desiccation and starvation following cold acclimation, heat hardening, desiccation hardening and starvation acclimation, resulting in 12 pretreatment-by-test combinations for estimating potential cross-resistance effects. The acclimation/hardening regimes were chosen so that flies enhanced their resistance to the same type of stress as that used for the particular pretreatment.

3. Two cases of cross-resistance were found, with desiccation-hardened and starvation-acclimated flies being more resistant than control ones in heat and desiccation resistance tests, respectively. In four cases, no acclimation/hardening effect was observed, and for six pretreatment-by-test combinations, the effect of acclimation/hardening was negative.

4. We also revealed that heat and desiccation hardening as well as acclimation to starvation had a cost under non-stressful conditions leading to reduced longevity. Cold acclimation did not affect longevity, although its effect was difficult to estimate precisely: during pretreatment at a low temperature, biological ageing of the flies might be delayed.

5. The pattern of acclimation/hardening responses considered in the context of literature data on stress resistance indicates that expression of heat-shock proteins is not likely to contribute to the observed cross-resistance, but other probable general stress resistance mechanisms such as reduction of metabolic rate and accumulation of energy reserves might be involved.

6. The lack of cross-resistance induced by acclimation/hardening treatments suggests that in an environment with multiple stresses, evolution of shared protective systems associated with plastic responses may be constrained.