Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
J Exp Biol. 2014 Jun 15;217(Pt 12):2193-200. doi: 10.1242/jeb.101931. Epub 2014 Apr 15.
We investigated the ecological physiology and behavior of free-living wood frogs [Lithobates (Rana) sylvaticus] overwintering in Interior Alaska by tracking animals into natural hibernacula, recording microclimate, and determining frog survival in spring. We measured cryoprotectant (glucose) concentrations and identified the presence of antifreeze glycolipids in tissues from subsamples of naturally freezing frogs. We also recorded the behavior of wood frogs preparing to freeze in artificial hibernacula, and tissue glucose concentrations in captive wood frogs frozen in the laboratory to -2.5°C. Wood frogs in natural hibernacula remained frozen for 193 ± 11 consecutive days and experienced average (October-May) temperatures of -6.3°C and average minimum temperatures of -14.6 ± 2.8°C (range -8.9 to -18.1°C) with 100% survival (N=18). Mean glucose concentrations were 13-fold higher in muscle, 10-fold higher in heart and 3.3-fold higher in liver in naturally freezing compared with laboratory frozen frogs. Antifreeze glycolipid was present in extracts from muscle and internal organs, but not skin, of frozen frogs. Wood frogs in Interior Alaska survive freezing to extreme limits and durations compared with those described in animals collected in southern Canada or the Midwestern United States. We hypothesize that this enhancement of freeze tolerance in Alaskan wood frogs is due to higher cryoprotectant levels that are produced by repeated freezing and thawing cycles experienced under natural conditions during early autumn.
我们通过跟踪进入自然冬眠地的动物、记录小气候以及确定春季青蛙的存活率，研究了在阿拉斯加内陆越冬的自由生活的林蛙（Lithobates (Rana) sylvaticus）的生态生理学和行为。我们测量了防冻剂（葡萄糖）浓度，并在自然冻结的青蛙组织样本中鉴定出抗冻糖脂的存在。我们还记录了在人工冬眠地准备冻结的林蛙的行为，以及在实验室中冻结到-2.5°C的圈养林蛙的组织葡萄糖浓度。在自然冬眠地中，林蛙连续冻结了 193±11 天，经历了平均（10 月至 5 月）-6.3°C 的温度和平均最低温度-14.6±2.8°C（范围-8.9 至-18.1°C），存活率为 100%（N=18）。与实验室冻结的青蛙相比，自然冻结的林蛙肌肉中的葡萄糖浓度高 13 倍，心脏中的葡萄糖浓度高 10 倍，肝脏中的葡萄糖浓度高 3.3 倍。抗冻糖脂存在于冻结青蛙的肌肉和内脏提取物中，但不存在于皮肤中。与在加拿大南部或美国中西部收集的动物相比，阿拉斯加的林蛙在冻结到极端极限和持续时间方面具有更强的耐寒性。我们假设，这种增强的抗冻性是由于在初秋的自然条件下经历的反复冻结和解冻循环产生了更高的防冻剂水平。
