New insights into survival strategies of tardigrades

Life is set within a narrow frame of physicochemical factors, yet, some species have adapted to conditions far beyond these constraints. Nature appears to have evolved two principal strategies for living organisms to cope with hostile conditions. One way is to remain active, retaining metabolism through adaptations that enable the organism to match the physiological requirements of environmental change. The other is to enter a state of dormancy with metabolic suppression. One form of metabolic suppression, known as cryptobiosis, is a widespread state across life kingdoms, in which metabolism comes to a reversible standstill. Among animals, nematodes, rotifers and tardigrades, comprise species that have the ability to enter cryptobiosis at all stages of their life cycle. Tardigrades are microscopic cosmopolitan metazoans found in permanent and temporal aquatic environments. They are renowned for their ability to tolerate extreme stress and are particularly resistant after having entered a cryptobiotic state known as a tun. As new molecular tools allow for a more detailed investigation into their enigmatic adaptations, tardigrades are gaining increasing attention. In this graphical review, we provide an outline of survival strategies found among tardigrades and we summarize current knowledge of the adaptive mechanisms that underlie their unique tolerance to extreme or changing environments

Automated summary

Life is constrained by physicochemical factors, but some species have adapted beyond these limits. Organisms have evolved two main strategies to cope with harsh conditions: remaining active with metabolism or entering dormancy with metabolic suppression. Tardigrades, microscopic metazoans found in aquatic environments, have the ability to enter a cryptobiotic state and tolerate extreme stress. Their unique adaptive mechanisms are gaining attention as new molecular tools allow for detailed investigation.