A GENETIC ANALYSIS OF TEMPORALLY-PROGRAMMED BEHAVIOR IN DROSOPHILA MELANOGASTER: CIRCADIAN RHYTHMS, ULTRADIAN RHYTHMS, AND THE ROLE OF BIOLOGICAL CLOCKS IN LEARNING

Selection for circadian rhythm variants in Drosophila melanogaster has led to the isolation of three new mutants all of which display an abnormal synchronization of daily rhythms to entraining cycles. Two of these new mutant strains (psi-2 and psi-3), when entrained to either light-dark or temperature cycles, have a distribution for adult emergence that is abnormally early. The emergence of adults in the third strain (gate) is poorly synchronized becoming nearly aperiodic in continuous darkness and constant temperature, conditions lacking temporal cues. All three of the variants segregate like single-gene mutations and can be genetically mapped to specific chromosomal intervals of the Drosophila genome. psi-2 and psi-3 also lengthen periods for the circadian rhythm of adult emergence. In addition, psi-2 brings about an abnormal synchronization of locomotor activity to light-dark cycles and lengthens periods for the activity rhythm. It is proposed that the psi mutations affect a factor which couples component oscillators comprising daily clocks.;An analysis of short-period endogenous rhythms in male courtship song of the new mutants verifies previous work (Kyriacou and Hall, 1980) suggesting a genetic relationship between circadian cycles and ultradian oscillations. psi-2, psi-3 and gate have comparable effects on this short-period oscillation (< 1 min) and on the daily rhythm of adult emergence.;Since the conditioned modification of behavior is, in many situations, dependent on a normal response to temporally-delivered stimuli, new and previously-isolated (Konopka and Benzer, 1971; Smith and Konopka, in preparation) clock mutations have been used to assess the role of endogenous timing mechanisms in learning. Two different experience-dependent modifications of male courtship behavior are disrupted in males that carry any of five independently-isolated mutations resulting in longer period biological rhythms. Males bearing mutations that either shorten periods or abolish rhythmic behavior express a normal modification of courtship behavior. Evidence is presented supporting the idea that the long-period clock mutations, rather than other multigenic factors, are responsible for the altered response to conditioning stimuli.;It could be supposed that the learning deficits observed in long-period mutants are caused by pleiotropic effects of clock mutations: i.e., that learning and biological rhythms are affected independently by clock mutations. The hypothesis that longer period rhythms, per se, disturb learning has been tested by examining the behavior of doubly-mutant males. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI...