水熊虫是一类具有卓越的极端环境耐受性的微型动物，隶属于泛节肢动物超门缓步动物门。它们能够在干燥、低温、高温及强辐射等极端恶劣条件下生存，其核心机制是通过脱水隐生(罐生)策略进入近乎停滞代谢的休眠状态，以抵御多种极端环境条件的胁迫。在分子层面，水熊虫会分泌热休克蛋白、缓步动物特异性无序蛋白以及海藻糖等保护性物质，以稳定细胞结构与生物大分子的完整性。在“灾难”来临时，水熊虫还会启动高效的抗氧化系统与DNA修复机制，共同构筑其非凡的环境耐受性，渡过难关。由于它们非凡的生命力，水熊虫曾多次被发射到太空参与实验，结果表明不少个体在太空真空、微重力及宇宙辐射下仍能存活，进一步证明它们是卓越的深空探索模式生物。

Water bears are microscopic animals renowned for their extraordinary tolerance to extreme environments, belonging  to the phylum Tardigrada within the broader Panarthropoda. They are capable of surviving under desiccation, extreme cold, high temperatures, and intense radiation. The mechanism underlying this resilience is their ability to enter a state of anhydrobiosis, a dehydrated cryptobiotic strategy in which metabolism nearly ceases, allowing them to withstand diverse environmental stresses. At the molecular level, tardigrades produce protective substances such as heat shock proteins, tardigrade-specific intrinsically disordered proteins, and trehalose, which help stabilize cellular structures and biomolecules. When confronted with environmental challenges, they also activate efficient antioxidant systems and DNA repair mechanisms, together forming the basis of their remarkable stress resistance. Because of their extraordinary vitality, tardigrades have been launched into space on multiple occasions. Experimental results show that a considerable number of individuals can survive exposure to the vacuum of space, microgravity, and cosmic radiation, further demonstrating their value as exceptional model organisms for deep-space exploration.