缓步以进入被称为隐生物的潜伏生命的极端耐受状态而闻名。虽然人们普遍认为,通过冷冻(冷冻)和干燥(脱水)可以诱发隐菌病,后者涉及形成所谓的隧道,这种状态的确切机制以及其他隐菌病诱导因素的意义仍然不明确。这里,我们专注于海洋潮汐缓步Echiniscoidessigismundi的渗透和化学胁迫耐受性。我们表明,西吉斯蒙迪在暴露于饱和海水后以及暴露于含有线粒体解偶联剂DNP的局部海水后进入tun状态。后面的实验提供了渗透生物和化学生物的证据,即,由高水平的渗透物和毒物诱导的隐生物,分别。同时暴露于DNP和饱和海水后,观察到存活率略有下降,这表明在渗透生物系统中,缓流可能不是完全代谢的。缓步容易处理暴露于超纯水,但是低渗休克会损害Tun的形成,当暴露于超纯水中时,缓流不会耐受DNP,表明对稀溶液的耐受性涉及耗能过程。我们讨论了与早期和更现代的隐生物研究有关的数据,我们认为渗透生物应被定义为由高外部渗透压引起的隐生物状态。我们的研究支持以下假设:渗透生物和脱水生物的潜在机制是重叠的,渗透生物可能代表了涉及体内水分剥夺的隐生形式的进化先驱。
Tardigrades are renowned for their ability to enter the extremotolerant state of latent life known as
cryptobiosis. While it is widely accepted that
cryptobiosis can be induced by freezing (cryobiosis) and by desiccation (anhydrobiosis), the latter involving formation of a so-called tun, the exact mechanisms underlying the state-as well as the significance of other cryptobiosis inducing factors-remain ambiguous. Here, we focus on osmotic and chemical stress tolerance in the marine tidal tardigrade Echiniscoides sigismundi. We show that E. sigismundi enters the tun state following exposure to saturated seawater and upon exposure to locality seawater containing the mitochondrial uncoupler DNP. The latter experiments provide evidence of osmobiosis and chemobiosis, i.e.,
cryptobiosis induced by high levels of osmolytes and toxicants, respectively. A small decrease in survival was observed following simultaneous exposure to DNP and saturated seawater indicating that the tardigrades may not be entirely ametabolic while in the osmobiotic tun. The tardigrades easily handle exposure to ultrapure water, but hypo-osmotic shock impairs tun formation and when exposed to ultrapure water the tardigrades do not tolerate DNP, indicating that tolerance towards dilute solutions involves energy-consuming processes. We discuss our data in relation to earlier and more contemporary studies on
cryptobiosis and we argue that osmobiosis should be defined as a state of
cryptobiosis induced by high external osmotic pressure. Our investigation supports the hypothesis that the mechanisms underlying osmobiosis and anhydrobiosis are overlapping and that osmobiosis likely represents the evolutionary forerunner of cryptobiosis forms that involve body water deprivation.