Tardigrades, commonly known as ‘water bears,’ are eight-legged microscopic invertebrates renowned for their ability to withstand extreme stressors. Limb retraction and substantial decreases to their internal water store results in the tun state, greatly increasing their ability to survive. Emergence from the tun state and activity regain follows stress removal, where resumption of life cycle occurs as if stasis never occurred. However, the mechanisms through which tardigrades initiate tun formation are still poorly understood. New research demonstrates that tardigrade tun formation is mediated by reactive oxygen species.
Tardigrades are famous for their ability to withstand extreme conditions, and can survive freezing, radiation, and environments without oxygen or water.
They persist by going dormant and entering a tun state, in which their bodies become dehydrated, their eight legs retract and their metabolism slows to almost undetectable levels.
Previously, little was known about what signals tardigrades to enter and leave this state.
“Tardigrades are a phylum of eight-legged microscopic invertebrates renowned for their remarkable ability to survive extreme environmental stressors,” said Dr. Amanda Smythers from the University of North Carolina at Chapel Hill and colleagues.
“This survival is rooted in their ability to initiate cryptobiosis, a physiological state wherein metabolism slows to near undetectable conditions, enabling long-term survival despite inhospitable conditions.”
“Although some eukaryotes and bacteria are capable of cryptobiosis, no eukaryotes are able to do so across the entirety of their lifespan, including as eggs, juveniles, and adults, or in response to such a broad range of stressors as tardigrades.”
“Thus tardigrades’ ability to survive desiccation, freezing, oxygen starvation, fluctuating osmotic pressure, and ionizing radiation (via anhydrobiosis, non tun-forming cryobiosis, anoxybiosis, osmobiosis, and…
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