Temperature-sensitive mutations in Drosophila melanogaster. VII. A mutation (para-ts) causing reversible adult paralysis.

A temperature-sensitive mutation, para(ts), in Drosophila melanogaster causes an immediate, but reversible, paralysis of adult flies when they are shifted from 22 degrees C to 29 degrees C. The mutation is a sex-linked recessive that maps 2.8 units to the left of f. Wild-type flies observed for 2-hr periods exhibited normal mobility at all temperatures between 22 degrees C and 35 degrees C. From 22 degrees C to 25 degrees C, para(ts) flies were wild type in walking, climbing, and flying ability. At 1-degree intervals above 25 degrees C, para(ts) flies became increasingly debilitated; at 29 degrees C, complete paralysis occurred. After flies were maintained for prolonged intervals at 29 degrees C, some activity could be recovered at that temperature. Studies of the behavior of mosaics at 29 degrees C revealed a requirement of the (+) allele in the head for mobility, and a thoracic component for proper leg movement. Normal electroretinograms were obtained at both 22 degrees C and 30 degrees C. The results suggest a temperature-sensitive defect in the nervous system.