Sperm morph and remating frequency in the Indian meal moth, Plodia interpunctella

All Lepidoptera produce two sperm types: normal, nucleated ‘eupyrene’ sperm and anucleate ‘apyrene’ sperm. One hypothesis for the evolution of apyrene sperm suggests that they act to reduce female remating rate. Apyrene sperm require less resources to produce than do eupyrene sperm, and could delay remating by females by acting as a “cheap filler”, packing the spermatheca and thereby reducing receptivity. This would reduce the risk of sperm competition, giving a potential adaptive advantage to the male producing these sperm. This leads to the prediction that the probability of a female remating should correlate with the number of stored apyrene sperm, which has previously been supported by experiments using the Green-Veined White butterfly, Pieris napi. We repeated this experiment using the Indian meal moth, Plodia interpunctella. We find that in this species eupyrene, not apyrene sperm number is the best predictor of female remating probability, indicating that the “cheap filler” hypot...所有鳞翅目（Lepidoptera）昆虫均产生两种精子：正常的、带有细胞核的真核精子（eupyrene sperm），以及无核的无核精子（apyrene sperm）。关于无核精子演化的一种假说提出，这类精子可降低雌性的再交尾率。相较于真核精子，无核精子的生产所需资源更少，可通过充当"廉价填充物"、填满雌性受精囊（spermatheca）从而降低其接受性，以此延缓雌性再次交尾。这一机制可减少精子竞争风险，为产生这类精子的雄性带来潜在的适应性优势。由此可预测，雌性再次交尾的概率应与储存的无核精子数量相关，此前这一假说已通过绿脉白蝶（*Pieris napi*）的相关实验得到验证。本研究以印度谷螟（*Plodia interpunctella*）为实验对象重复了该实验。我们发现，在该物种中，能够最佳预测雌性再交尾概率的是真核精子数量，而非无核精子数量，这表明"廉价填充物"假说……