Kanazawa Mai, Nanri Takahiro, Saigusa Masayuki
1 Department of Biology, Faculty of Science, Okayama University, Tsushima 3-1-1, Okayama-Kitaku 700-8530, Japan.
2 Section of Research and Education, The Biosphere Project (Non-Profit Organization), Tsushima-Fukui 1-8-71, Okayama-Kitaku 700-0080, Japan.
Zoolog Sci. 2017 Apr;34(2):81-85. doi: 10.2108/zs160057.
The bdelloid rotifer of the genus Adineta is a freshwater metazoan characterized by anhydrobiosis, a highly stable state of suspended animation induced by desiccation. This study investigated the influence of anhydrobiosis on the thermal habituation by use of an index, Activity Ratio (AR = the number of active rotifers at each experimental temperature/ number of active rotifers at the 25°C stage). In the first experiment, rotifers were divided into two groups: one group was cultivated at 25°C throughout experiment, and another group was transferred to 15°C for two days. AR was estimated during heating up to 40°C, or during cooling down to 5°C in each group. The largest difference in AR occurred at 35°C and 10°C, indicating that AR was changed depending on the pretreated medium temperature. In the next experiment, rotifers were maintained at 15°C, and were desiccated (anhydrobiosis). AR was estimated in the high temperature range (25°C to 40°C), using rotifers that had recovered from anhydrobiosis. AR was significantly different between the groups with and without desiccation, suggesting that thermal habituation at 15°C was completely cancelled by anhydrobiosis. Possible mechanisms on the influence of anhydrobiosis on the thermal habituation have been discussed in terms of neural changes and proteins.
艾氏蛭形轮虫属的蛭形轮虫是一种淡水后生动物，其特征是具有隐生现象，即由干燥诱导产生的一种高度稳定的假死状态。本研究通过使用一个指标——活动率（AR = 每个实验温度下活跃轮虫的数量/25°C阶段活跃轮虫的数量）来研究隐生现象对热适应性的影响。在第一个实验中，轮虫被分为两组：一组在整个实验过程中都在25°C下培养，另一组被转移到15°C下培养两天。在每组升温至40°C或降温至5°C的过程中估计AR。AR的最大差异出现在35°C和10°C时，这表明AR根据预处理的培养基温度而变化。在下一个实验中，轮虫在15°C下维持培养，然后进行干燥处理（隐生）。使用从隐生状态恢复的轮虫，在高温范围（25°C至40°C）内估计AR。有干燥处理和没有干燥处理的组之间AR存在显著差异，这表明15°C下的热适应性被隐生现象完全消除。关于隐生现象对热适应性影响的可能机制已从神经变化和蛋白质方面进行了讨论。
