Daphnia magna and Daphnia pulex are two important model species in ecotoxicology. In daphniids, studies of the effects of contaminants have mostly focused on female life history traits, yet it would also be important to examine male reproductive traits, particularly in relation to endocrine disruptors. In this study, we developed a protocol that uses flow cytometry to measure sperm number in individual males of different species of Daphnia. We tested our protocol on 114 males from several clones of three common species of Daphnia. Sperm count varied widely among individuals and reached high numbers (up to 1.45 × 10⁵). Positive relationships between male length and sperm number were observed in D. pulex and Daphnia pulicaria, but not in D. magna. Important inter‐clonal differences in sperm production were observed in all species, with some clones producing very little sperm. Duplicated sperm samples showed on average only 6% difference in sperm counts. Sperm counts were stable at least over a 2‐hr period and up to 5 hr for most samples. This sperm isolation protocol and flow cytometric enumeration approach will be of major interest to ecotoxicologists.

中文翻译：

---

通过流式细胞术评估的水蚤物种（甲壳纲，克拉多菌）的精子数量

水蚤（Daphnia magna）和水蚤（Daphnia pulex）是生态毒理学中的两个重要模型物种。在蚤形鱼类中，对污染物影响的研究主要集中在女性的生活史特征上，但是检查男性生殖特征，特别是与内分泌干扰物有关的特征也很重要。在这项研究中，我们开发了一种协议，该协议使用流式细胞术来测量水蚤不同物种的雄性中的精子数量。我们在三种水蚤的三种常见克隆的114个雄性中测试了我们的方案。每个人的精子数量差异很大，并且数量很高（高达1.45×10 ⁵）。D. pulex的雄性长度与精子数量呈正相关和水蚤（Daphnia pulicaria），但不在D. magna中。在所有物种中均观察到重要的克隆间精子产生差异，有些克隆产生的精子很少。重复的精子样本显示平均只有6％的精子差异。精子计数至少在2小时内保持稳定，而大多数样品的精子计数在5小时内稳定。这种精子分离方案和流式细胞计数方法将是生态毒理学家的主要兴趣。