MALE-MALE COURTSHIP BEHAVIOR INDUCED BY ECTOPIC EXPRESSION OF THE DROSOPHILA WHITE GENE - ROLE OF SENSORY FUNCTION AND AGE

Male-male courtship behavior was recently reported to be induced in la rge populations of Drosophila (e.g., 600-1500 flies) by ectopic expres sion of the white (w) gene. Little is known about the basis of this be haviour; in male-female courtship, sensory cues are believed to play a n important role. Previous data are consistent with the possibility th at misexpression of w causes abnormal reception or processing of senso ry information. We show here that w-induced male-male courtship occurs in isolated pairs of flies. Thus the behavior does not depend on sens ory cues found only among large populations of flies, or on cues produ ced only by a small subset of such populations. This finding enabled q uantitative analysis of mechanisms that underlie the behavior. Specifi cally, male-male courtship does not depend on the reception of olfacto ry information, nor on the reception or generation of auditory cues, a s determined by surgical ablation of antennae, maxillary palps, or win gs. Although the rapid onset of the behavior following w induction sug gested that its basis could lie in a modulation of sensory physiology, we found visual, olfactory, and gustatory function to be normal in ph ysiological or behavioral tests. The only sensory deprivation to produ ce an effect on male-male courtship was testing under dim red light; t he percentage of flies courting another male was reduced to one-fourth of control values. A striking age dependence of the behavior is also documented: courtship between paired male mini-w(+) flies was not obse rved in tests of very young (1-day-old) flies, but occurs at high leve ls between the ages of 1 and 4 weeks. (C) 1996 John Wiley & Sons, Inc.