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A Cystophorous Cercaria, C. projecta n.sp., from the Snail, Helisoma antrosa, North America

Published online by Cambridge University Press:  06 April 2009

Charles H. Willey
Charles H. Willey
Affiliation:
Department of Biology, University College, New York University.
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Extract

A new species of larval trematode, C. projecta, infects Helisoma antrosa. The very small distome cercaria is ontogenetically young, showing no traces of reproductive anlagen even after excystment. It belongs to the cystophorous cercariae, and has a vesicular tail into which the body of the cercaria withdraws when mature. In this encysted state the cercaria is expelled from the snail and awaits ingestion by the next host. The redia is a large, elongate sac, without “feet,” possessing a small pharynx, short intestine and an excretory system consisting of a longitudinal channel and at least sixty flame cells on each side of the body. Excystment is caused by mechanical pressure which releases a force within the cyst, which projects the cercaria very rapidly through a long cuticular tube, the excretory projection, to a considerable distance away from the cyst. Various complex appendages of the tail vesicle along with parts of the excretory system play a large part in this process of excystment. As postulated, the purpose of this type of excystment is to throw the larva away from its cyst, to prevent it from being regurgitated from the body with the empty cyst.

Type
Research Article
Information
Parasitology , Volume 22 , Issue 4 , October 1930 , pp. 481 - 489
Copyright
Copyright © Cambridge University Press 1930

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