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Gametocyte sex ratio in single-clone infections of the malaria parasite Plasmodium mexicanum

Published online by Cambridge University Press:  12 July 2010

A.T. NEAL  and
J.J. SCHALL
A.T. NEAL*
Affiliation:
Department of Biology, University of Vermont, Burlington, Vermont05405, USA
J.J. SCHALL
Affiliation:
Department of Biology, University of Vermont, Burlington, Vermont05405, USA
*
*Corresponding author: Department of Biology, University of Vermont, Burlington, Vermont, 05405, USA. Tel: 001 802 656 0702. Fax: 001 802 656 2914. E-mail: aneal@uvm.edu
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Summary

Sex ratio theory predicts that malaria parasites should bias gametocyte production toward female cells in single-clone infections because they will experience complete inbreeding of parasite gametes within the vector. A higher proportion of male gametocytes is favoured under conditions that reduce success of male gametes at reaching females such as low gametocyte density or attack of the immune system later in the infection. Recent experimental studies reveal genetic variation for gametocyte sex ratio in single-clone infections. We examined these issues with a study of experimental single-clone infections for the lizard malaria parasite Plasmodium mexicanum in its natural host. Gametocyte sex ratios of replicate single-clone infections were determined over a period of 3–4 months. Sex ratios were generally female biased, but not as strongly as expected under simple sex ratio theory. Gametocyte density was not related to sex ratio, and male gametocytes did not become more common later in infections. The apparent surplus of male gametocytes could be explained if male fecundity is low in this parasite, or if rapid clotting of the lizard blood reduces male gamete mobility. There was also a significant clone effect on sex ratio, suggesting genetic variation for some life-history trait, possibly male fecundity.

Keywords

sex ratioPlasmodiummalariasex allocationPlasmodium mexicanumgametocyteLocal Mate Competitionfertility insurancesingle-clone infections
Type
Research Article
Information
Parasitology , Volume 137 , Issue 13 , November 2010 , pp. 1851 - 1859
Copyright
Copyright © Cambridge University Press 2010

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