The Drosophila mutant shibire (shits) is temperature-sensitive. At 27–28°C, a red-eyed stock of shits lost phototaxis and became paralyzed, then died within 24h. A different stock of the same allele of shits flies, which was white-eyed, was still active even if temperature was elevated to 30°C. Both red- and white-eyed shits flies showed normal electroretinographic (ERG) waveforms at 24–25°C, a permissive temperature. When shi flies were cooled to 10–11°C, no obvious ERG changes were observed in the white-eyed stock, but on- and off-transients disappeared in the red-eyed stock. When red-eyed shits and white-eyed shits flies were warmed to their restrictive temperatures of 28.5 and 39°C, respectively, the on- and off-transients disappeared within minutes. In white-eyed shits, the restrictive temperature increased with post-eclosion age. To assay differences in visual pigment turnover, we measured the absorbance difference of visual pigment by microspectrophotometry [MSP] at 25 and 35°C, respectively. The absorbance difference decreased slightly with time when the white-eyed shits flies were warmed to 35°C.
