Molecular simulation modelling of the circadian system of the blow fly, Lucilia cuprina

The Australian sheep blow fly, Lucilia cuprina, is a day active calliphorid whose larval stages are facultative parasites of sheep. As a calliphorid, L. cuprina provides an interesting comparative platform to examine the conservation of circadian timing mechanisms in the Diptera. Here we describe the development of a quantitative dynamic simulation model for the circadian system of L. cuprina which is based on data concerning the molecular nature of the feedback loop in Drosophila and is modified to account for the basic behavioural differences between Lucilia and Drosophila. The model provides a representation of behavioural rhythmicity and the underlying molecular oscillations which generate this rhythmicity. Some of the basic molecular assumptions of the model have been supported by cloning a full length L. cuprina per cDNA and expression analysis of this gene (Warman et al., Genetical Research Cambridge 75 (2000) 257). Having produced a biochemically valid model, its predictive power was tested. Simulations of the response of the circadian system to constant bright and constant dim light were validated at a behavioural level and the model was used to predict the molecular changes underlying these behavioural responses. The integration of molecular data with classical approaches to chronobiological modelling leads to improved insight into the functioning of dipteran circadian systems.