Rasmussen L M, Holmstrup M
National Environmental Research Institute, Department of Terrestrial Ecology, Vejlsøvej 25, PO Box 314, DK-8600 Silkeborg, Denmark.
J Comp Physiol B. 2002 Dec;172(8):691-8. doi: 10.1007/s00360-002-0298-4. Epub 2002 Sep 20.
Freeze-tolerance and some of the underlying biochemical defence mechanisms in the earthworm Dendrobaena octaedra was investigated. Survival after slow cooling to -2 degrees C, -4 degrees C, or -6 degrees C was analysed in D. octaedra from three geographic regions representing large differences in winter temperature (Denmark, Finland and Greenland). A large variation in freeze-tolerance between the three populations of D. octaedra was found. Earthworms from the northern populations (Finland and Greenland) tolerated lower temperatures (-6 degrees C) than earthworms from the Danish population (poor survival at -4 degrees C and -2 degrees C). In the Finnish population, freezing led to the production of high concentrations of glucose, which reached values much higher than controls (94 mg g(-1) vs. 2 mg g(-1) dry weight). Other potential cryoprotectants were not elevated after freezing. The Danish and Greenlandic populations had substantially lower mean glucose levels after freezing than the Finnish population (about 15 mg g(-1)). Danish earthworms rapidly frozen did not accumulate glucose, and did not survive freezing at -2 degrees C. Danish earthworms exposed to osmotic stress in Ringer's solutions, containing different concentrations of glycerol, showed significantly elevated glucose levels, but did not survive rapid freezing. It was determined if freezing had an influence on the reproduction of the earthworms. After warming to summer temperatures (15 degrees C), survivors of freezing produced viable cocoons. In a field experiment it was tested if natural acclimatization during autumn and winter months had an effect on freeze-tolerance in the Danish population. There was a significant increase of post-freeze survival during this period. The results of the freezing experiments are discussed in relation to the general ecology of D. octaedra.
对八毛枝蚓（Dendrobaena octaedra）的抗冻能力及一些潜在的生化防御机制进行了研究。分析了来自代表冬季温度差异较大的三个地理区域（丹麦、芬兰和格陵兰）的八毛枝蚓在缓慢冷却至-2℃、-4℃或-6℃后的存活率。发现八毛枝蚓的三个种群之间的抗冻能力存在很大差异。来自北方种群（芬兰和格陵兰）的蚯蚓比丹麦种群的蚯蚓能耐受更低的温度（-6℃）（丹麦种群在-4℃和-2℃时存活率较低）。在芬兰种群中，冷冻导致产生高浓度的葡萄糖，其含量远高于对照组（94毫克/克干重 vs. 2毫克/克干重）。冷冻后其他潜在的抗冻剂并未升高。丹麦和格陵兰种群冷冻后的平均葡萄糖水平明显低于芬兰种群（约15毫克/克）。快速冷冻的丹麦蚯蚓不积累葡萄糖，且在-2℃下冷冻不能存活。暴露于含有不同浓度甘油的林格氏溶液中的渗透胁迫下的丹麦蚯蚓，其葡萄糖水平显著升高，但快速冷冻后不能存活。研究了冷冻是否对蚯蚓的繁殖有影响。升温至夏季温度（15℃）后，冷冻的幸存者产生了有活力的茧。在一项田间实验中，测试了秋冬季节的自然驯化是否对丹麦种群的抗冻能力有影响。在此期间，冷冻后的存活率显著提高。结合八毛枝蚓的一般生态学对冷冻实验结果进行了讨论。
