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Host-finding in Trichobilharzia ocellata cercariae: swimming and attachment to the host

Published online by Cambridge University Press:  06 April 2009

W. Feiler
Affiliation:
Institut für Zoologie I, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-8520 Erlangen, Federal Republic of Germany
W. Haas*
Affiliation:
Institut für Zoologie I, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-8520 Erlangen, Federal Republic of Germany
*
To whom reprint requests and correspondence should be addressed

Summary

The cercaria of Trichobilharzia ocellata finds and identifies its duck host with a seriesof different behavioural phases. Dispersal and selection of the water surface as microhabitat is achieved by an intermittent swimming behaviour, which is governed by the interplay of passive dropping with forward and backward swimming movements and includes a positive phototactic and a geonegative orientation. Then the cercariae tend to cling to the water surface in an energy-saving resting position. A movement towards the duck feet as the site of entry occurs when shadows evoke forward swimming movements, which are directed away from the source of light, i.e. normally downwards. Forward swimming movements are also stimulated by touch, but only in free-swimming cercariae and not when these are in the resting position. Attachments occur only when a substrate is touched during forward swimming movements. Attachments are stimulated by warm substrates (1 °C temperature difference triggers a nearly maximal response) and by chemical components of duck-foot skin, and the readiness to attach is increased when the forward swimming movement is started by shadow stimuli.

Information

Type
Research Article
Copyright
Copyright © Cambridge University Press 1988

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