EFFECTS OF TEMPERATURE ON VISUAL RECEPTORS IN TEMPERATURE-SENSITIVE PARALYTIC SHIBIRE (SHI(TS))

The Drosophila mutant shibire (shi(ts)) is temperature-sensitive. At 2 7-28-degrees-C, a red-eyed stock of shi(ts) lost phototaxis and became paralyzed, then died within 24 h. A different stock of the same allel e of shi(ts) flies, which was white-eyed, was still active even if tem perature was elevated to 30-degrees-C. Both red- and white-eyed shi(ts ) flies showed normal electroretinographic (ERG) waveforms at 24-25-de grees-C, a permissive temperature. When shi flies were cooled to 10-11 -degrees-C, no obvious ERG changes were observed in the white-eyed sto ck, but on- and off-transients disappeared in the red-eyed stock. When red-eyed shi(ts) and white-eyed shi(ts) flies were warmed to their re strictive temperatures of 28.5 and 39-degrees-C, respectively, the on- and off-transients disappeared within minutes. In white-eyed shi(ts), the restrictive temperature increased with post-eclosion age. To assa y differences in visual pigment turnover, we measured the absorbance d ifference of visual pigment by microspectrophotometry [MSP] at 25 and 35-degrees-C, respectively. The absorbance difference decreased slight ly with time when the white-eyed shi(ts) flies were warmed to 35-degre es-C.