College of Biological Sciences, School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, 305-8572, Tsukuba, Ibaraki, Japan.
Master's Program in Biology, Degree Programs in Life and Earth Sciences, Graduate School of Science and Technology, University of Tsukuba, 1‑1‑1 Tennodai, 305‑8572, Tsukuba, Ibaraki, Japan.
Exp Appl Acarol. 2023 Oct;91(2):251-262. doi: 10.1007/s10493-023-00842-y. Epub 2023 Oct 4.
In many animals, males increase their reproductive success by mating with as many females as possible. The number of females a male can fertilize is often limited by male competition for access to females, sperm competition, and the cost of sperm production. Especially, recent studies have shown that sperm production is more costly than previously expected. In the two-spotted spider mite, Tetranychus urticae Koch, the number of females a male can inseminate is limited mainly by male competition for access to females. However, in the absence of rivals, males mate with so many females that they can become sperm-depleted. Mating without sperm transfer does not produce any offspring, although it takes time and energy. Therefore, a question arises as to why males continue to mate even after sperm depletion. In this study, we hypothesized that males continue to mate because sperm is replenished after a short period. To test the hypothesis, we investigated how long it takes for sperm replenishment after sperm depletion. We found that in 3 h, sperm can be replenished enough to inseminate a few females. As 3 h is sufficiently short not to lose the next mating opportunity, the results support the hypothesis. However, copulation duration in the sperm-replenished males was significantly longer than in the sperm-depleted males but shorter than in males before sperm depletion. To explain the differences, further research would be necessary. In addition, anatomical physiology study in males is also required to confirm that sperm is indeed depleted and replenished.
在许多动物中，雄性通过尽可能多地与雌性交配来提高其繁殖成功率。雄性能够使多少只雌性受精通常受到雄性对雌性的竞争、精子竞争和精子生产成本的限制。特别是，最近的研究表明，精子的生产成本比以前预期的要高。在二斑叶螨（Tetranychus urticae Koch）中，雄性能够使雌性受精的数量主要受到雄性对雌性的竞争限制。然而，在没有竞争对手的情况下，雄性与如此多的雌性交配，以至于它们可能会精疲力尽。虽然交配不需要转移精子，但它需要时间和能量，并且不会产生任何后代。因此，出现了一个问题，即为什么雄性在精子耗尽后仍然继续交配。在这项研究中，我们假设雄性继续交配是因为在短时间内精子就会得到补充。为了验证这个假设，我们研究了在精子耗尽后精子补充需要多长时间。我们发现，在 3 小时内，精子可以得到足够的补充，从而使几只雌性受精。由于 3 小时的时间足够短，不会错过下一个交配机会，因此结果支持了这个假设。然而，在精子补充后的雄性的交配持续时间明显长于精子耗尽后的雄性，但短于精子耗尽前的雄性。为了解释这些差异，需要进一步的研究。此外，还需要对雄性进行解剖生理学研究，以确认精子确实被耗尽和补充。
