Barbora Konopova

1 Introduction Across the globe, more than 5% of mammalian species, representing several orders, spend most of their lives in moist and dark, oxygen-poor and carbon dioxide-rich, self-constructed underground burrow systems that are deprived of most sensory cues available aboveground. These mammals are specialized for their unique way of life, conducting all essential activities, including foraging, mating, breeding and sleeping, underground.

eLife assessment This important study presents findings regarding the role of Juvenile Hormone in development and cell differentiation in the ametabolous insect Thermobia domestica, providing an in-depth analysis of JH's roles in a member of this basally branching group. The evidence supporting the claims of the authors is convincing, drawing on a broad range of approaches and variety of experimental techniques.

Abstract To gain insights into how juvenile hormone (JH) came to regulate insect metamorphosis, we studied its function in the ametabolous firebrat, Thermobia domestica. Highest levels of JH occur during late embryogenesis, with only low levels thereafter. Loss-of-function and gain-of-function experiments show that JH acts on embryonic tissues to suppress morphogenesis and cell determination and to promote their terminal differentiation.