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The effect of light and darkness on the production of cercariae of Schistosoma haematobium from Bulinus globosus

Published online by Cambridge University Press:  05 June 2009

K. M. Raymond  and
A. J. Probert
K. M. Raymond
Affiliation:
School of Animal Biology, University College of North Wales, Bangor, UK
A. J. Probert
Affiliation:
School of Animal Biology, University College of North Wales, Bangor, UK
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Abstract

The cercariae of Schistosoma haematobium showed a diurnal periodicity of emergence from Bulinus globosus in a twelve hour light/dark cycle. Peak emission occurred at 11.00 hrs with a smaller peak at 20.00 hrs, following the start of the period of darkness. In continuous illumination this second peak was not seen, indicating that only the morning peak is circadian in origin. The evening peak occurs in response to dark treatment and can be produced by periods of darkness ranging from eight seconds to one hour. The longer the period of dark treatment the longer the rise in output is maintained on return to light conditions. Subjection of snails to periods of dark treatment during the normal light period caused a reduction in the evening peak with the largest effect seen following the longest period of darkness. An increased output of cercariae was seen following fifteen minutes exposure to a range of light intensities, the largest increase occurring at 10 000 and 7000 lux and complete darkness. The rapidity of this reaction to variations in light intensity suggests that the cercariae of S. haematobium are showing emergence in response to shadows.

Keywords

Schistosoma haematobiumBulinus globosuscercarial emergenceperiodicity
Type
Research Papers
Information
Journal of Helminthology , Volume 61 , Issue 4 , December 1987 , pp. 291 - 296
Copyright
Copyright © Cambridge University Press 1987

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References

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