Summary 1. Adult Drosophila melanogaster Meigen were examined for Hsp70 expression level and heat‐shock resistance from 0 to 8 days of age – the latter being close to the mean life span in natural D. melanogaster populations. 2. Over the 8 days, both induced Hsp70 expression level and induced heat‐shock resistance showed a linear decrease. Heat‐shock resistance without prior hardening also decreased, but at a lower rate than both induced Hsp70 expression level and heat‐shock resistance after hardening. 3. The results suggest that the decrease in induced Hsp70 expression level in D. melanogaster with age is regulatory and not due to a reduced ability to express Hsp70 as a result of senescence. 4. The changes in induced Hsp70 expression level with age are likely to be determined by natural selection and are evolutionarily adaptive. The decrease with age in stress resistance after hardening may then be considered a direct consequence of age‐dependent reduction in expression levels of induced Hsp70.
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Sørensen et al. (2002) studied this question.