New reproductive anomalies in fruitless-mutant Drosophila males: Extreme lengthening of mating durations and infertility correlated with defective serotonergic innervation of reproductive organs

Several features of male reproductive behavior are under the neural control of fruitless (fru) in Drosophila melanogaster. This gene is known to influ ence courtship steps prior to mating, due to the absence of attempted copul ation in the behavioral repertoire of most types of fru-mutant males. Howev er, certain combinations of fru mutations allow for fertility. By analyzing such matings and their consequences, we uncovered two striking defects: ma ting times up to four times the normal average duration of copulation; and frequent infertility, regardless of the time of mating by a given transhete rozygous fru-mutant male. The lengthened copulation times may be connected with fru-induced defects in the Formation of a male-specific abdominal musc le, production of sperm and certain seminal fluid proteins are normal in th ese fru mutants. However, analysis of postmating qualities of females that copulated with transheterozygous mutants strongly implied defects in the ab ility of these males to transfer sperm and seminal fluids. Such abnormaliti es may be associated with certain serotonergic neurons in the abdominal gan glion in which production of 5HT is regulated by fru. These cells send proc esses to contractile muscles of the male's internal ses organs; such projec tion patterns are aberrant in the semifertile foe mutants. Therefore, the r eproductive functions regulated by fruitless are expanded in their scope, e ncompassing not only the earliest stages of courtship behavior along with a lmost all subsequent steps in the behavioral sequence, but also more than o ne component of the culminating events. (C) 2001 John Wiley & Sons, Inc.