Cripe G M, Hemmer B L, Goodman L R, Vennari J C
Gulf Ecology Division, Office of Research and Development, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Gulf Breeze, FL 32561, USA.
Arch Environ Contam Toxicol. 2009 Apr;56(3):500-8. doi: 10.1007/s00244-008-9204-8. Epub 2008 Aug 14.
Evaluation of effects on fish reproduction and development during chemical exposures lasting for multiple generations is sometimes limited by variable reproductive responses and the time required for the exposure. Established testing methods and the short life cycle of the sheepshead minnow, Cyprinodon variegatus, make this species particularly suitable for use in identifying potential impacts of contaminants in estuarine and marine environments. This study describes the refinement of life-cycle exposure methods that increased the reliability of reproduction in sheepshead minnows and reduced the time to maturation for larvae and juvenile fishes. A test of three spawning chamber designs, three sex ratios, and two photoperiods identified conditions that reduced the coefficient of variation in egg production from >100% to as little as 32%. The most reliable results were produced with groups of three female and two male fishes (all of similar size) when they were placed in a rectangular chamber and acclimated for 12 days. A test water temperature of 26.5 +/- 2 degrees C and a 14L:10D photoperiod resulted in fish producing a mean of 74 embryos per female per day, with a coefficient of variation of 31.8%. Egg fertility exceeded 90%, with a hatch rate of 95% for normal embryos (>or=80% yolk) and a hatch rate of <or=45% for embryos containing <or=77% yolk. The length of time to grow larvae to spawning adult fish was reduced to approximately 60 days posthatch by feeding them flake food twice daily to satiation for 15 min, and it was observed that size (>or=2.7 cm standard length) was critical for spawning readiness. Adult fish were prepared for the spawning assessment by adding frozen brine shrimp to their diet. Results of these experiments provide methods that are of particular interest in assessment of endocrine-disrupting chemicals that are known to affect reproduction.
在对持续多代的化学物质暴露期间鱼类繁殖和发育的影响进行评估时，有时会受到生殖反应的变异性以及暴露所需时间的限制。已确立的测试方法以及羊头鲦鱼（Cyprinodon variegatus）较短的生命周期，使得该物种特别适合用于识别河口和海洋环境中污染物的潜在影响。本研究描述了生命周期暴露方法的改进，这些改进提高了羊头鲦鱼繁殖的可靠性，并缩短了幼鱼和稚鱼成熟所需的时间。对三种产卵室设计、三种性别比例和两种光周期的测试确定了一些条件，这些条件将产蛋量的变异系数从>100%降低到了低至32%。当将三组大小相似的雌鱼和两条雄鱼放置在一个矩形产卵室中并适应12天时，得到了最可靠的结果。测试水温为26.5±2摄氏度，光周期为14小时光照：10小时黑暗，结果是每条雌鱼每天平均产74个胚胎，变异系数为31.8%。卵的受精率超过90%，正常胚胎（卵黄≥80%）的孵化率为95%，卵黄≤77%的胚胎孵化率≤45%。通过每天两次投喂片状食物至饱食15分钟，将幼鱼生长至产卵成鱼的时间缩短至孵化后约60天，并且观察到大小（标准长度≥2.7厘米）对于产卵准备至关重要。通过在成年鱼的饮食中添加冷冻盐水虾来为产卵评估做准备。这些实验的结果提供了一些方法，这些方法对于评估已知会影响繁殖的内分泌干扰化学物质特别有意义。
