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The daily cercarial emission rhythm of Schistosoma margrebowiei with particular reference to dark period stimuli

Published online by Cambridge University Press:  05 June 2009

K. Raymond  and
A. J. Probert
K. Raymond
Affiliation:
School of Biological Sciences, University of Wales, Bangor, Gwynedd LL57 2UW, UK
A. J. Probert
Affiliation:
School of Biological Sciences, University of Wales, Bangor, Gwynedd LL57 2UW, UK
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Abstract

The cercariae of Schistosoma margrebowiei showed two peaks of emergence from Bulinus natalensis in a 12 h light/dark cycle. Peak emission occurred at 0700 h (one hour after the onset of light) and at 1900 h (one hour after the onset of darkness). Both peaks were of equal magnitude and were maintained during constant illumination indicating that the rhythm is innate. Delaying or advancing the timing of the dark period did not affect the timing of these two peaks. Following a five minute dark treatment elevation in cercarial output resulted irrespective of when the treatment was applied. Subjecting snails to various intensities of light only resulted in an elevation in output when a sudden change in intensity from 0 to 360 Lux or the reverse was applied. No response was seen to a gradual change in light intensity although the parasite could detect a change in light from 1 to 0 Lux. These responses appear to optimize the chances of host parasite contact.

Keywords

Schistosoma margrebowieiBulinus natalensiscercarial emergenceperiodicityTrematoda
Type
Research Papers
Information
Journal of Helminthology , Volume 65 , Issue 3 , September 1991 , pp. 159 - 168
Copyright
Copyright © Cambridge University Press 1991

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References

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