Renfree M B, Shaw G
Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.
Annu Rev Physiol. 2000;62:353-75. doi: 10.1146/annurev.physiol.62.1.353.
Embryonic diapause, or delayed implantation as it is sometimes known, is said to occur when the conceptus enters a state of suspended animation at the blastocyst stage of development. Blastocysts may either cease cell division so that their size and cell numbers remain constant, or undergo a period of very slow growth with minimal cell division and expansion. Diapause has independently evolved on many occasions. There are almost 100 mammals in seven different mammalian orders that undergo diapause. In some groups, such as rodents, kangaroos, and mustelids, it is widespread, whereas others such as the Artiodactyla have only a single representative (the roe deer). In each family the characteristics of diapause differ, and the specific controls vary widely from lactational to seasonal, from estrogen to progesterone, or from photoperiod to nutritional. Prolactin is a key hormone controlling the endocrine milieu of diapause in many species, but paradoxically it may act either to stimulate or inhibit growth and activity of the corpus luteum. Whatever the species-specific mechanisms, the ecological result of diapause is one of synchronization: It effectively lengthens the active gestation period, which allows mating to occur and young to be born at times of the year optimal for that species.
胚胎滞育，有时也被称为延迟着床，据说是指当孕体在发育的囊胚阶段进入一种假死状态时发生的现象。囊胚可能会停止细胞分裂，使其大小和细胞数量保持不变，或者经历一段细胞分裂和扩张极少的非常缓慢的生长时期。滞育在许多情况下是独立进化而来的。在七个不同的哺乳纲目中，有近100种哺乳动物会经历滞育。在一些类群中，如啮齿动物、袋鼠和鼬科动物，滞育现象很普遍，而其他类群，如偶蹄目，只有一个代表物种（狍）。在每个科中，滞育的特征都不同，具体的控制因素差异很大，从泌乳到季节、从雌激素到孕酮、或者从光周期到营养等方面都有所不同。催乳素是控制许多物种滞育内分泌环境的关键激素，但矛盾的是，它可能既刺激也抑制黄体的生长和活性。无论物种特异性机制如何，滞育的生态结果是同步化之一：它有效地延长了活跃妊娠期，使交配能够发生，幼崽能够在一年中对该物种最适宜的时间出生。
