Department of Zoology, Miami University, Oxford, OH 45056, USA.
J Exp Biol. 2013 Jun 1;216(Pt 11):1961-7. doi: 10.1242/jeb.070268.
Ectothermic vertebrates have colonized regions that are seasonally or perpetually cold, and some species, particularly terrestrial hibernators, must cope with temperatures that fall substantially below 0°C. Survival of such excursions depends on either freeze avoidance through supercooling or freeze tolerance. Supercooling, a metastable state in which body fluids remain liquid below the equilibrium freezing/melting point, is promoted by physiological responses that protect against chilling injury and by anatomical and behavioral traits that limit risk of inoculative freezing by environmental ice and ice-nucleating agents. Freeze tolerance evolved from responses to fundamental stresses to permit survival of the freezing of a substantial amount of body water under thermal and temporal conditions of ecological relevance. Survival of freezing is promoted by a complex suite of molecular, biochemical and physiological responses that limit cell death from excessive shrinkage, damage to macromolecules and membranes, metabolic perturbation and oxidative stress. Although freeze avoidance and freeze tolerance generally are mutually exclusive strategies, a few species can switch between them, the mode used in a particular instance of chilling depending on prevailing physiological and environmental conditions.
变温脊椎动物已经占领了季节性或永久性寒冷的地区，一些物种，特别是陆生冬眠动物，必须应对远低于 0°C 的温度。这种迁徙的生存取决于通过过冷却避免冻结还是通过抗冻结能力来应对。过冷却，即体液在平衡冰点以下仍保持液态的亚稳状态，通过保护免受冷害的生理反应和限制环境冰和冰核形成剂引起的接种性冻结风险的解剖学和行为特征来促进。抗冻结能力是从对基本压力的反应进化而来的，以使大量身体水分在与生态相关的热和时间条件下冻结时能够存活。冻结的生存受到一系列复杂的分子、生化和生理反应的促进，这些反应限制了因过度收缩、大分子和膜损伤、代谢扰动和氧化应激而导致的细胞死亡。尽管避免冻结和抗冻结能力通常是相互排斥的策略，但少数物种可以在它们之间切换，在特定的寒冷情况下使用哪种模式取决于当前的生理和环境条件。
