Hala David N, Van Look Katrien, Holt William V, Jobling Susan
Institute for the Environment, Brunel University, Uxbridge, London, UK UB8 3PH.
ILAR J. 2009;50(4):e1-e10. doi: 10.1093/ilar.50.4.e1.
The fathead minnow (Pimephales promelas) is an OECD-proposed test species routinely used in reproductive toxicity trials with suspected endocrine-disrupting compounds (EDCs). The basic fecundity, endocrinology, and histopathology of reproductively active male and female fathead minnows has been well characterized, but there are few studies of the utility of male sperm concentration and motility as endpoints for use in reproductive trials. The purpose of this study was to (1) characterize the baseline sperm concentration and motility of pair-breeding male fathead minnows over their spawning cycle and (2) determine whether a repeated and nondestructive sperm sampling protocol would influence the baseline fecundity of the fish. Pair-breeding male fathead minnows that underwent sampling for milt three times a week for 4 weeks exhibited no significant changes in milt volume, sperm concentration, or motility parameters up to 6 days after each spawning event. The repeated sperm sampling procedure did, however, cause a significant lowering of spawning frequencies, although this decline did not correlate with effects on fecundity as there were no significant changes in the mean total numbers of eggs laid, fertilization, and hatching successes. This study confirmed the presence of a stable background of sperm concentration and motility parameters of pair-breeding male fathead minnows under reference conditions. The absence of any inherent "cycling" in the magnitude of these parameters over the spawning period suggests that sperm concentration and motility could be useful measures of male reproductive toxicity at the termination of tests in which pair-breeding males are at varying days post spawn.
黑头呆鱼（Pimephales promelas）是经济合作与发展组织（OECD）提议的试验物种，常用于对疑似内分泌干扰化合物（EDC）进行生殖毒性试验。具有生殖活性的雄性和雌性黑头呆鱼的基本繁殖力、内分泌学和组织病理学已得到充分表征，但关于将雄性精子浓度和活力作为生殖试验终点的效用的研究较少。本研究的目的是：（1）描述成对繁殖的雄性黑头呆鱼在产卵周期内的基线精子浓度和活力；（2）确定重复且非破坏性的精子采样方案是否会影响鱼的基线繁殖力。每周对成对繁殖的雄性黑头呆鱼采精3次，持续4周，在每次产卵事件后的6天内，其精液体积、精子浓度或活力参数均无显著变化。然而，重复的精子采样程序确实导致产卵频率显著降低，不过这种下降与对繁殖力的影响无关，因为产卵总数、受精率和孵化成功率的平均值没有显著变化。本研究证实，在参考条件下，成对繁殖的雄性黑头呆鱼存在稳定的精子浓度和活力参数背景。在产卵期内这些参数的大小不存在任何固有的“周期性”变化，这表明在对成对繁殖雄性进行不同产后天数的试验结束时，精子浓度和活力可能是衡量雄性生殖毒性的有用指标。
