INDUCTION AND DECAY OF THERMOSENSITIVITY IN THE FLESH FLY, SARCOPHAGA-CRASSIPALPIS

When pharate adults of the flesh fly Sarcophaga crassipalpis are expos ed to 40-degrees-C for 4 h they become more tolerant of high temperatu res that are normally lethal (thermotolerance). In contrast, a 1-h exp osure to 45-degrees-C decreases tolerance to a subsequent high tempera ture challenge (thermosensitivity). While control flies experience lit tle mortality when held at 35-degrees-C for 24-48 h the thermosensitiz ed flies die when exposed to 35-degrees-C. Sensitivity to a second the rmal challenge slowly decays over a 72-h period. The acquisition of th ermotolerance prevents the development of thermosensitivity. Brains fr om thermosensitized flies cultured at 43-degrees-C express the 72-kDa heat-shock protein and normal protein synthesis is inhibited. This imp lies that development of thermosensitivity is not associated with a lo ss in the capacity to express the 72-kDa heat-shock protein.