Mutant <i>Drosophila melanogaster</i> flies with drastically altered free-running periods of locomotor activity (<i>period</i> mutants) were used to investigate the relationship between circadian control of overt rhythm production and photoperiodic time measurement. Comparison of the free-running rhythms of wild-type, short period and long period mutants revealed that alterations in this periodicity resulted from a decrease in the active phase (short <i>period</i> mutant) or an increase in the inactive phase (long <i>period</i> mutant) when compared with wild-type. Light phase response curves were determined for light pulses of different durations which suggested that the mutants also had an altered sensitivity to light. Comparisons of the photoperiodic response of these strains revealed a remarkable similarity from which it was concluded that the <i>period</i> locus is not essential for PPTM but may be involved in a peripheral role. The light PRC data were used to model the CDL of the photoperiodic response in the wild-type, short <i>period</i> and long <i>period</i> mutants and the modelled results did not agree with the experimental ones. A feedback model for photoperiodic time measurement involving two oscillations, a pacemaker controlling overt rhythmicity and weakly coupled to a slave involved in PPTM was shown to replicate the experimental results. In conclusion, although the locomotor activity rhythm and the photoperiodic time measuring system are both governed by circadian oscillators, they are believed to be, at best, weakly coupled together so that the oscillator controlling locomotor activity may play a role in photoperiodism.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:651482 |
| Date | January 1993 |
| Creators | Gillanders, S. W. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14915 |
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