ABSTRACT: In polygynous species, the sperm economy hypothesis predicts that males can adjust the amount of their ejaculate during copulation in response to (1) individual traits of females according to potential female fecundity, (2) future mating opportunities, and (3) risk of sperm competition. We tested this hypothesis in the crab Metacarcinus edwardsii by performing laboratory mating experiments to compare the response of males (sperm number and ejaculate weight delivered) in 3 sex-ratio scenarios: (1) equal, 1 female:1 male; (2) male-biased, 1 female:2 males; and (3) female-biased, 2 females:1 male. First, we determined if any variable, or an interaction between variables, could explain the variation in sperm or ejaculate amount delivered under an equal sex ratio. Second, we contrasted the ejaculate allocation among different sex-ratio scenarios. Under an equal sex ratio, males of M. edwardsii did not adjust their ejaculate allocation in response to any female trait. Male size was positively related to ejaculate delivery, indicating that the pair of vasa deferentia has ejaculate reserves that scale exponentially with male size. However, larger males delivered disproportionally more seminal fluid than sperm. Under a female-biased sex ratio, males did not show plasticity in their ejaculate allocation, but they increased their ejaculate investment (23%) per female under a male-biased sex ratio (i.e. risk of sperm competition). M. edwardsii presented a low level of ejaculate allocation, responding only when competitive males were perceived. In species with trans-molt sperm retention and long ejaculate storage, the risk of sperm competition is present all the time; therefore, males do not economize ejaculate even if more receptive females are available.

中文翻译：

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Brachyura的射精分配：爱德华Meta骨的雄性对什么有反应？

摘要：在多生种物种中，精子经济假说预测，雄性可以在交配过程中调节其射精量，以响应（1）根据潜在雌性繁殖力，（2）未来交配机会和（3）风险的雌性个体特征。精子竞争。我们在爱德华氏蟹蟹中验证了这一假设通过进行实验室交配实验，比较三种性别比例下的男性反应（精子数量和射出的射精重量）：( 1）相等，1女性：1男性；（2）男性偏见，女性1：男性2；（3）女性偏见，2位女性：1位男性。首先，我们确定是否有任何变量或变量之间的相互作用可以解释在性别平等的情况下精子或射精量的变化。其次，我们对比了不同性别比例情况下的射精分配。在性别平等的情况下，爱德华氏菌的男性没有针对任何女性特征调整射精分配。雄性大小与射精量呈正相关，表明这对输卵管的射精储备量与雄性大小成指数关系。但是，较大的男性比精子不成比例地输送更多的精液。在以女性为偏见的性别比例下，男性的射精分配没有表现出可塑性，但在以男性为偏见的性别比例下（即，有精子竞争的风险），他们增加了每名女性的射精投资（23％）。爱德华氏菌表现出低水平的射精分配，仅在感知到有竞争能力的男性时才做出反应。在具有蜕皮精子保留和长时间射精的物种中，精子竞争的风险一直存在。因此，即使有更多接受能力强的雌性，雄性也不能节省射精。