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Pallisentis rexus from the Chiang Mai Basin, Thailand: ultrastructural studies on egg envelope development and the mechanism of egg expansion

Published online by Cambridge University Press:  12 April 2024

W. Wongkham  and
P.J. Whitfield
W. Wongkham
Affiliation:
Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand:
P.J. Whitfield*
Affiliation:
School of Health and Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NN, UK
*
*Author for correspondence Fax: 020 7848 4195 E-mail: phil.whitfield@kcl.ac.uk
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Abstract

Pallisentis rexus Wongkham & Whitfield, 1999 (Eoacanthocephala: Quadrigyridae) infects the freshwater snakehead fish, Channa striata, in the Chiang Mai Basin, Thailand. All stages of egg development within the body cavity of the female parasite were observed, using transmission electron microscopy. Changes in mature eggs after contact with water were also investigated. The mature egg has five egg envelopes separated from each other by four gaps. The fertilization membrane, which is formed first, is pushed centrifugally by other, subsequently formed, envelopes and gaps, which produces a final total shell thickness of 8–36 μm around the acanthor. The disappearance of the outermost layer and the unpleating of an adjacent inner layer causes the expansion of eggs on contact with water. The volume of an expanded egg is approximately 27 times that of an unexpanded one, but the density of eggs is reduced from a value greater than water to one almost equal to water. This is believed to aid the dispersion of eggs.

Type
Research Article
Information
Journal of Helminthology , Volume 78 , Issue 1 , March 2004 , pp. 77 - 85
Copyright
Copyright © Cambridge University Press 2004

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