Mating Systems and Sperm Competition in Insects

为了了解昆虫的交配系统，对三个分类群的精子竞争机制进行了研究。观察到粉尘菊蝇的雄性使用三种不同的策略来获得配偶。在三种观察策略中，交配的平均持续时间不同，导致不同程度的精子取出和受精。研究了可能影响交配持续时间的各种因素。最重要的是雄性捕食配偶的地点。瓜蝇Dacus cucurbitae的雄性交配持续10小时或更长时间，通常从黎明开始，到黄昏结束。受精后转移到雌性体内的精子数量随着时间的延长而增加。当雌性进行双重交配时，交配持续时间是父子关系的主要决定因素。然而，当交配间隔超过10天时，精子优先的“最后雄性优势”被观察到。显微镜下计数受精囊中的精子数，估计精子的平均寿命为17天。由于第一次雄性的精子在第二次交配之前死亡的比例，精子优先值将在没有任何精子置换机制的情况下增加。研究了粘虫幼虫饲养密度与精荚大小的关系。在高密度条件下生长的雄性比单独生长的雄性产生更大的精荚，尽管它们的体型没有差别。精巢大小随着雄性年龄或前次交配与当前交配间隔时间的延长而增大。接受较大精囊的雌性比接受较小精囊的雌性延迟了更长时间。

Mechanisms of sperm competition in three taxonomical groups of insects was studied in order to understand their mating systems.1. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tactics to secure mates. The mean duration of copulation differed between the three observed tactics and resulted in varying degrees of sperm removal and insemination. A variety of factors which might influence copulation duration were invesitgated. The most important was the location of the site at which males captured thier mates.2. Males of the melon fly Dacus cucurbitae copulate for 10 hours or more, usually starting at dawn and terminating at dusk. The amount of sperm transferred to a female increased with time after mounting. Mating duration was a major determinant of paternity when females were doubly mated. However, "last male's advantage" in sperm precedence was observed when the mating interval was longer than 10 days. Counting the number of sperm in spermatheca under a microscope, mean longevity of sperm was estimated as 17 days. As a proportion of the first male's sperm die before a second mating has occurred, sperm precedence value would increase without any sperm displacement mechanism.3. Variation in spermatophore size was studied in relation to larval rearing density in the armyworm, Leucania separata. Males grew under a high density condition produced larger spermatophore than solitary males, in spite that the body size was not different between them. Spermatophore size increased with male age or time interval between previous and current matings. Females that received large spermatophore delayed remating longer than those receiving small ones.