Department of Biology, University of Vermont, Burlington, VT 05405, USA.
Parasitology. 2011 Sep;138(10):1203-10. doi: 10.1017/S0031182011000941. Epub 2011 Jul 15.
Evolutionary theory predicts that the sex ratio of Plasmodium gametocytes will be determined by the number of gametes produced per male gametocyte (male fecundity), parasite clonal diversity and any factor that reduces male gametes' ability to find and combine with female gametes. Despite the importance of male gametocyte fecundity for sex ratio theory as applied to malaria parasites, few data are available on gamete production by male gametocytes. In this study, exflagellating gametes, a measure of male fecundity, were counted for 866 gametocytes from 26 natural infections of the lizard malaria parasite, Plasmodium mexicanum. The maximum male fecundity observed was 8, but most gametocytes produced 2-3 gametes, a value consistent with the typical sex ratio observed for P. mexicanum. Male gametocytes in infections with higher gametocytaemia had lower fecundity. Male fecundity was not correlated with gametocyte size, but differed among infections, suggesting genetic variation for fecundity. Fecundity and sex ratio were correlated (more female gametocytes with higher fecundity) as predicted by theory. Results agree with evolutionary theory, but also suggest a possible tradeoff between production time and fecundity, which could explain the low fecundity of this species, the variation among infections, and the correlation with gametocytaemia.
进化理论预测，疟原虫配子体的性别比例将由每个雄配子体产生的配子数量（雄配子生殖力）、寄生虫克隆多样性以及任何降低雄配子寻找和与雌配子结合能力的因素决定。尽管雄性配子生殖力对适用于疟原虫的性别比例理论很重要，但关于雄性配子体产生配子的资料很少。在这项研究中，为了研究蜥蜴疟原虫 Plasmodium mexicanum 的 26 种自然感染情况，对 866 个配子体进行了鞭毛配子（衡量雄性生殖力的指标）计数。观察到的最大雄性生殖力为 8，但大多数配子体产生 2-3 个配子，这一数值与 Plasmodium mexicanum 观察到的典型性别比例一致。在配子体血症较高的感染中，雄性配子体的生殖力较低。雄性生殖力与配子体大小无关，但在感染之间存在差异，这表明生殖力存在遗传变异。生殖力和性别比例呈正相关（生殖力较高的雌性配子体更多），这与理论预测一致。结果与进化理论一致，但也表明在生产时间和生殖力之间可能存在权衡，这可以解释该物种的低生殖力、感染之间的变异以及与配子体血症的相关性。
