ANALYSIS OF CONDITIONED COURTSHIP IN DUSKY-ANDANTE RHYTHM MUTANTS OF DROSOPHILA

Genetic connections between learning and rhythmicity were suggested to have been established in a previous study, in part because the dusky( Andante) (dy(And)) mutation in Drosophila disrupted both behaviors. dy (And), isolated as a slow-clock variant, was reported to cause an appr oximately fourfold decrement in courtship-suppression conditioning. Th ese effects have been reexamined; the experiments were buttressed by t esting the effects of several recently isolated mutations at the dusky locus, along with the original And allele that had been induced there . The reexamination was also prompted by anatomical concerns, certain of which have recently focused on dy-induced decrements in cell size, but only in terms of wing morphology. Another anatomical issue involve s the discovery of a neuronal pathway that seems to connect circadian pacemaker cells to a structure in the Drosophila brain that is involve d in learning. In observer-blind experiments, however, it was found th at neither pacemaker-slowing (Andante-like) dy mutations nor others th at cause no rhythm defects produced subnormal conditioned courtship. M oreover, in the adult brain of a slow-clock dy(And) mutant, no axonal pathway defects were readily discernible and putative pacemaker neuron s appeared to be normal in size.