Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe image on the cover features embryos of the freshwater cnidarian Hydra vulgaris. Hydra spp. are cosmopolitan inhabitants of lakes, ponds, and rivers. Although they commonly reproduce through asexual budding, they can also reproduce sexually. As Hydra embryos develop, they are encased within a protective theca that appears as a translucent “halo” around the opaque circular embryos in the image. On pages 111–118 R. E. Steele et al. demonstrate that Hydra embryos hatch sporadically, even after as much as a year of dormancy. They also report the discovery of Hydra polyps in a vernal pool that completely dries out each year and is refilled only by rainwater. They consider that the Hydra polyps are likely either to be dispersed by birds or animals or to persist in a desiccated state until the pond is filled again. In either case, this would likely involve theca-stage embryos. The authors propose that dormancy in Hydra may have evolved as a bet-hedging strategy in unstable environments.Many different types of animals can enter into dormancy, ranging from rotifers and copepods to fish and mammals. Broadly, dormancy can allow animals to persist through adverse environmental conditions, spread reproductive risk, and optimize seasonal phenology. As with Hydra, dormancy sometimes allows animals to disperse to environments that would otherwise be unreachable. As oceans warm and environments change, the relationship between dormancy cues, such as temperature and photoperiod, can shift, with as yet unknown effects on the timing of dormancy and resulting ecosystem dynamics. Our understanding of the mechanisms that regulate dormancy is rapidly increasing, enabled by the application of modern “omics” methods to a diverse suite of organisms. Ecological studies are revealing complex linkages between environmental and genetic regulation of dormancy, roles of dormant stages in maintaining diversity, and cascading consequences of shifts in the timing of dormancy. This symposium issue explores the diversity of strategies for dormancy and examines cross-cutting themes in the regulation of dormancy physiology.Credits: Photo of embryos, Robert E. Steele, University of California, Irvine; png image of globe, pCC BY-NC 4.0. Cover design, Jeannie Harrell, University of Chicago Press, and Ann M. Tarrant, Woods Hole Oceanographic Institution. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 237, Number 2October 2019 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/707330 © 2019 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.