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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4537

T. Kreuels, R. Joerres, Wolfgang Martin, and Klaus Brinkmann; System Analysis of the Circadian Rhythm of Euglena gracilis, II: Masing Effects and Mutual Interactions of Light and Temperature Responses. Z.Naturforsch. 39c:801-811, 1984

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Motility of Euglena gracilis shows free running circadian rhythms. The circadian system is sensitive to light and temperature signals, but it is always marked by direct responses of motility to light (photokinesis) and temperature (thermokinesis). By means of a compartimental model which defines the interrelations between the pathways of thermokinesis, photokinesis and the circadian system a unifying view of effects of temperature and light input signals is outlined. According to the model, and using double sine input signals the dynamics of thermokinesis is described by a differential amplifier with constant gain. Although thermokinesis heavily masks circadian responses to temperature signals, the limited range of circadian entrainment is indirectly demonstrated by a limited reappearance of free running circadian oscillations after stopping the temperature program. Free running circadian oscillations do reappear only after pretreatment with temperature periods near the circadian eigenperiod. A white mutant lacking photosynthesis is used to investigate the role of photosynthesis in the signal processing. Although light synchronizes the circadian rhythms of the white mutant if applied as single input, it does not affect the motility of applied together with temperature inputs near the circadian eigenperiod. These results indicate frequency dependent mutual interactions between the model compartments.