Marcus Nancy H
Biol Bull. 1987 Aug;173(1):169-177. doi: 10.2307/1541870.
The duration of diapause of Labidocera aestiva eggs collected from the field and reared in the laboratory was determined at 5°C. A clear seasonal trend was observed. Diapause eggs produced in the early fall required a much longer exposure to cold to yield a 50% hatch (CT) (i.e., the duration of diapause was longer) than eggs produced later in the fall. Eggs produced by laboratory animals that were reared at 14°C, 8L-16D, required a shorter period of chilling to terminate diapause than the eggs of animals reared at 19° C, 12L-12D. Considerable variation in the CT value was also observed among laboratory cultures that were all reared under identical conditions, but which differed in terms of selection history. The results indicate that both the genotype of the egg and the conditions prevailing during oocyte formation influence the duration of diapause. Eggs that were stored at 5°C for periods longer than 300 days no longer hatched upon warming. It is suggested that the variation in the duration of diapause is an adaptation that promotes synchronization of hatching by ensuring that all individuals terminate diapause at approximately the same time, and survival during the winter by conferring cold-hardiness. Synchronizing the onset of post-diapause development is also discussed as an alternative mechanism for achieving synchronous hatching.
对从野外采集并在实验室饲养的艾氏歪水蚤（Labidocera aestiva）卵在5°C下的滞育持续时间进行了测定。观察到了明显的季节性趋势。秋季早期产生的滞育卵比秋季后期产生的卵需要更长时间的低温暴露才能达到50%孵化率（CT）（即滞育持续时间更长）。在14°C、8小时光照 - 16小时黑暗条件下饲养的实验动物所产的卵，与在19°C、12小时光照 - 12小时黑暗条件下饲养的动物所产的卵相比，终止滞育所需的低温处理时间更短。在相同条件下饲养但选择历史不同的实验室培养物中，也观察到CT值存在相当大的差异。结果表明，卵的基因型以及卵母细胞形成期间的环境条件都会影响滞育持续时间。在5°C下储存超过300天的卵在升温后不再孵化。有人认为，滞育持续时间的变化是一种适应性特征，通过确保所有个体大致在同一时间终止滞育来促进孵化同步，并通过赋予抗寒能力来保证冬季存活。文中还讨论了使滞育后发育同步开始作为实现同步孵化的另一种机制。
