Department of Biology, Faculty of Science and Engineering, Konan University, Kobe, 658-8501, Japan.
Institute for Integrative Neurobiology, Konan University, Kobe, 658-8501, Japan.
Sci Rep. 2023 Mar 1;13(1):3029. doi: 10.1038/s41598-023-29705-7.
After copulation, insect females store sperm in a spermatheca for some duration until fertilization. At the beginning of their adult lives, ant queens can preserve numerous viable sperm cells from copulation for over ten years. However, the key factors influencing long-term sperm storage have not been identified. Here we show that the spermathecal environment is nearly anoxic, which induces sperm immobilization. Furthermore, mitochondrial respiratory inhibitors suppress sperm motility, suggesting that sperm immobilization may be caused by a shortage of ATP generated from only glycolysis under near-anoxic conditions. Sperm immobilization is not induced by acidification via glycolytic metabolism because the spermathecal fluid is not acidic. Finally, we show that artificial anoxic conditions rather than aerobic conditions sustain viable sperm cells. Therefore, near-anoxia is a key factor influencing long-term sperm storage in ant queens. The viability of sperm cells under artificial anoxia, however, is lower than that of those dissected immediately from queens. Moreover, the immotile sperm cells under more than 4 h of anoxia do not begin swimming after aerobic exposure, unlike those under anoxic conditions for less than 2 h. This finding indicates that factors other than anoxia are also necessary for long-term sperm preservation.
交配后，昆虫雌性会将精子储存在精囊内一段时间，直到受精。在它们成年生活的开始，蚂蚁蚁后可以从交配中保存大量存活的精子细胞超过十年。然而，影响长期精子储存的关键因素尚未确定。在这里，我们表明精囊内环境几乎是缺氧的，这会导致精子失活。此外，线粒体呼吸抑制剂抑制精子运动，表明在近缺氧条件下，仅由糖酵解产生的 ATP 短缺可能导致精子失活。精子失活不是由糖酵解代谢引起的酸化引起的，因为精囊液不是酸性的。最后，我们表明人工缺氧条件而不是有氧条件维持有活力的精子细胞。因此，近缺氧是影响蚂蚁蚁后长期精子储存的关键因素。然而，在人工缺氧下的精子细胞的活力低于从蚁后中立即分离出来的精子细胞的活力。此外，在超过 4 小时的缺氧下，失活的精子细胞在有氧暴露后不会开始游动，而在缺氧条件下不到 2 小时则不会。这一发现表明，除了缺氧之外，还有其他因素也需要长期保存精子。
