Abstract
cacophony (cac), a mutation affecting the courtship song in Drosophila melanogaster, is revealed to cause temperature-sensitive (TS) abnormalities. When exposed to high temperatures (37 degrees), cac flies show frequent convulsions and pronounced locomotor defects. This TS phenotype seems consistent with the idea that cac is a mutation in a calcium-channel gene; it maps to the same X-chromosomal locus that encodes the polypeptide comprising the alpha-1 subunit of this membrane protein. Analysis of the courtship song of some TS physiological mutants showed that slowpoke mutations, which affect a calcium-activated potassium channel, cause severe song abnormalities. Certain additional TS mutants, in particular para(ts1) and nap(ts1), exhibit subtler song defects. The results therefore suggest that genes involved in ion-channel function are a potential source of intraspecific genetic variation for song parameters, such as the number of cycles present in "pulses" of tone or the rate at which pulses are produced by the male's courtship wing vibrations. The implications of these findings from the perspective of interspecific lovesong variations in Drosophila are discussed.