An in-depth look at the basic aspects of dormancy in cyclic parthenogenetic organisms is now possible thanks to research efforts conducted over the past two decades with rotifer dormant embryos. In this review, we assemble and compose the current knowledge on four central themes: (1) distribution of dormancy in animals, with an overview on the phylogenetic distribution of embryo dormancy in metazoans, and (2) physiological and cellular processes involved in dormancy, with a strong emphasis on the dormant embryos of cyclically parthenogenetic monogonont rotifers; and discussions of (3) the selective pressures and (4) the evolutionary and population implications of dormancy in these animals. Dormancy in metazoans is a widespread phenomenon with taxon-specific features, and rotifers are among the animals in which dormancy is an intrinsic feature of their life cycle. Our review shows that embryo dormancy in rotifers shares common functional pathways with other taxa at the molecular and cellular level, despite the independent evolution of dormancy across phyla. These pathways include the arrest of similar metabolic routes and the usage of common metabolites for the stabilization of cellular structures and to confer stress resistance. We conclude that specific features of recurrent harsh environmental conditions are a powerful selective pressure for the fine-tuning of dormancy patterns in rotifers. We hypothesize that similar mechanisms at the organism level will lead to similar adaptive consequences at the population level across taxa, among which the formation of egg banks, the coexistence of species, and the possibility of differentiation among populations and local adaptation stand out. Our review shows how studies of rotifers have contributed to improved knowledge of all of these aspects.

中文翻译：

---

面对逆境：轮虫中的休眠胚胎

由于过去二十年对轮虫休眠胚胎进行的研究工作，现在可以深入了解循环孤雌生殖生物休眠的基本方面。在这篇综述中，我们汇集并撰写了关于四个中心主题的当前知识：（1）动物休眠的分布，概述了后生动物胚胎休眠的系统发育分布，以及（2）休眠涉及的生理和细胞过程，重点关注周期性单性生殖轮虫的休眠胚胎；和讨论（3）选择压力和（4）休眠对这些动物的进化和种群影响。后生动物的休眠是一种具有分类群特异性特征的普遍现象，轮虫是休眠是其生命周期内在特征的动物之一。我们的综述表明，尽管休眠在整个门中独立进化，但轮虫的胚胎休眠在分子和细胞水平上与其他分类群共享共同的功能途径。这些途径包括阻止相似的代谢途径和使用共同代谢物来稳定细胞结构和赋予抗压性。我们得出结论，反复出现的恶劣环境条件的特​​定特征是微调轮虫休眠模式的强大选择压力。我们假设生物体水平上的类似机制将导致整个分类群在种群水平上产生类似的适应性后果，其中包括卵库的形成、物种的共存、人群差异化和地方适应的可能性突出。我们的评论显示了轮虫研究如何有助于提高所有这些方面的知识。