三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响

近年来越来越多研究表明,雄性产生精子(精液)也需付出代价。在多次交配的动物中,雄性为获得最大生殖潜力,必须依据配偶的质量策略性地调整每次交配的生殖投入。雄性策略性的生殖投入主要体现在两个方面,一是精子竞争(sperm competition),二是柯立芝效应(Coolidge effect)。目前精子竞争研究主要集中于昆虫类群,而柯立芝效应研究集中于高等脊椎动物,同时验证结果也时常与假说不一致。以多次交配的三突伊氏蛛为材料,以雄蛛交配行为为指标,在蜘蛛类群中探讨和验证雄性精子竞争强度假说和柯立芝效应。设定3个交配组合:2只雄蛛依次与1只雌蛛各交配1次(A组)、2只雄蛛依次与2只雌蛛各交配1次(B组)和1只雄蛛与1只雌蛛交配2次(C组),分析比较3个交配组合的三突伊氏蛛第1次交配和第2次交配在交配潜伏期、交配持续时间和交配回合数方面的差异,比较三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响,以此验证雄性精子竞争强度假说和柯立芝效应。研究结果表明A和B组的三突伊氏蛛第2次交配的交配潜伏期和交配持续时间显著长于第1次交配。同时,C组的三突伊氏蛛第1次交配的交配潜伏期和交配持续时间与第2次交配都没有显著差异。同时,A、B和C组的三突伊氏蛛第1次交配的交配回合数与第2次交配都没有显著差异。研究结果支持精子竞争强度假说,而不支持柯立芝效应。

Effects of female mating history on male mating behavior in the crab spider Ebrechtella tricuspidata

Sperm (ejaculate) production is known to be costly to males across diverse taxa. Consequently, depending on mate quality, mated males are predicted to strategically allocate their ejaculate so as to maximize their reproductive success. Such male strategies include sperm competition and the Coolidge effect. Sperm competition is widely explored in a wide range of insect taxa, whereas studies on the Coolidge effect have mainly focused on vertebrates. Nevertheless, the results are often inconsistent with the predictions. In the present study, our aim was to test the hypotheses of sperm competition intensity and Coolidge effect by analyzing the effects of female mating history (in the crab spider Ebrechtella tricuspidata) on male mating behavior. By manipulating mating histories of both females and males, we designed three mating groups: Group A (2 virgin males copulated with 1 virgin female 1 time in sequence), Group B (1 virgin male and 1 previously mated-once male copulated with 1 female 1 time in sequence), and Group C (1 male copulated with 1 female 2 times). We compared the differences in male courtship latency, mating duration, and mating bouts between the first and second mating across the 3 mating groups. The mating latency and mating duration of the second mating were significantly longer than those of the first mating in groups A and B. In contrast, there was no significant difference in mating latency and mating duration between the first and second mating in Group C. Furthermore, there was no significant difference in the mating bouts between the first and second mating across the 3 mating groups. Our results suggest that male E. tricuspidata may be able to detect female mating history and strategically allocate their reproductive investment in terms of mating latency and mating duration. When a male "believed" that the female had mated previously with a rival, this male prolonged his mating duration (reproductive investment). When a male repeatedly mated with the same female, the male did not significantly shorten his mating duration in the second mating relative to the first one, as predicted by the hypothesis of the Coolidge effect. Taken together, our data support the model of sperm competition intensity, but contradict the Coolidge effect. To our knowledge, this is the first study to test sperm competition and the Coolidge effect in spiders.