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Once an embryo starts developing, it usually doesn’t stop. Unless that embryo happens to be an African turquoise killifish, Nothobranchius furzeri. These fish must survive long dry seasons in which their transient ponds evaporate from under them. To make it ‘til the next rainy season, embryos will enter a period of suspended development called diapause.

But all is not idle—a new study in Science reveals the patterns of gene activity that let the developing fish hit pause yet come out unscathed months later.

The team of researchers, led by Anne Brunet at Stanford, assembled a transcriptomic time course for killifish embryos in diapause to determine gene expression at different points. In particular, they observed that a collection of chromatin regulators in the Polycomb complex kick in while the embryos are otherwise shut down, preserving organ tissues and muscles until it rains down in Africa again.