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Causes of intraspecific variation in body size among trematode metacercariae

Published online by Cambridge University Press:  01 September 2009

I. Saldanha ,
T.L.F. Leung  and
R. Poulin
I. Saldanha
Affiliation:
Department of Zoology, University of Otago, PO Box 56, Dunedin9054, New Zealand
T.L.F. Leung
Affiliation:
Department of Zoology, University of Otago, PO Box 56, Dunedin9054, New Zealand
R. Poulin*
Affiliation:
Department of Zoology, University of Otago, PO Box 56, Dunedin9054, New Zealand
*
*E-mail: [email protected]
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Abstract

Inequalities in body size among adult helminths can result in inequalities in reproductive output, with consequences for population dynamics and genetics. These inequalities can result from growth differences among larval worms inside intermediate hosts that persist into the adult stage. Here, we investigate the effects of both host body size and intensity of infection on the sizes of metacercariae of the trematode Maritrema novaezealandensis (Microphallidae) inside their second intermediate host, the isopod Paridotea ungulata (Idoteidae). Among the more than 1500 metacercariae recovered and individually measured, there was no relationship between the mean diameter of metacercarial cysts per isopod and isopod body length. However, intensity of infection correlated negatively with the mean diameter of cysts within an isopod, i.e. metacercariae in crowded infections attained smaller sizes on average. In contrast, the variability in cyst sizes per isopod, measured as the coefficient of variation, was independent of both isopod body length and infection intensity. Our results show that a disproportionate number of relatively small metacercariae come from the relatively few hosts in which a large fraction of all metacercariae are aggregated. The combination of aggregation and intensity-dependent growth generates inequalities in sizes among metacercariae that will be passed on to adult worm populations in definitive hosts.

Type
Research Papers
Information
Journal of Helminthology , Volume 83 , Issue 3 , September 2009 , pp. 289 - 293
Copyright
Copyright © Cambridge University Press 2009

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