Temperature-Sensitive Mutations in <i>Drosophila melanogaster</i> , VII. A Mutation ( <i> para ^ts </i> ) 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°C to 29°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°C and 35°C. From 22°C to 25°C, para ts flies were wild type in walking, climbing, and flying ability. At 1-degree intervals above 25°C, para ts flies became increasingly debilitated; at 29°C, complete paralysis occurred. After flies were maintained for prolonged intervals at 29°C, some activity could be recovered at that temperature. Studies of the behavior of mosaics at 29°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°C and 30°C. The results suggest a temperature-sensitive defect in the nervous system.