Shams Imad, Avivi Aaron, Nevo Eviatar
Laboratory of Animal Molecular Evolution, Institute of Evolution, University of Haifa, Mt. Carmel, Haifa 31905, Israel.
Comp Biochem Physiol A Mol Integr Physiol. 2005 Nov;142(3):376-82. doi: 10.1016/j.cbpa.2005.09.003. Epub 2005 Oct 11.
The composition of oxygen (O2), carbon dioxide (CO2), and soil humidity in the underground burrows from three species of the Israeli subterranean mole rat Spalax ehrenbergi superspecies were studied in their natural habitat. Two geographically close populations of each species from contrasting soil types were probed. Maximal CO2 levels (6.1%) and minimal O2 levels (7.2%) were recorded in northern Israel in the breeding mounds of S. carmeli in a flooded, poor drained field of heavy clay soil with very high volumetric water content. The patterns of gas fluctuations during the measurement period among the different Spalax species studied were similar. The more significant differentiation in gas levels was not among species, but between neighboring populations inhabiting heavy soils or light soils: O2 was lower and CO2 was higher in the heavy soils (clay and basaltic) compared to the relatively light soils (terra rossa and rendzina). The extreme values of gas concentration, which occurred during the rainy season, seemed to fluctuate with partial flooding of the tunnels, animal digging activity, and over-crowded breeding mounds inhabited by a nursing female and her offspring. The gas composition and soil water content in neighboring sites with different soil types indicated large differences in the levels of hypoxic-hypercapnic stress in different populations of the same species. A growing number of genes associated with hypoxic stress have been shown to exhibit structural and functional differences between the subterranean Spalax and the above-ground rat (Rattus norvegicus), probably reflecting the molecular adaptations that Spalax went through during 40 million years of evolution to survive efficiently in the severe fluctuations in gas composition in the underground habitat.
在以色列三种东非鼹形鼠（Spalax ehrenbergi 超种）地下洞穴的自然栖息地，对氧气（O₂）、二氧化碳（CO₂）的组成以及土壤湿度进行了研究。对来自两种不同土壤类型、地理上相邻的每个物种的两个种群进行了探测。在以色列北部，卡氏东非鼹形鼠（S. carmeli）繁殖丘中记录到了最高二氧化碳水平（6.1%）和最低氧气水平（7.2%），该繁殖丘位于一个水淹、排水不良的重粘土田，体积含水量非常高。在研究的不同东非鼹形鼠物种测量期间，气体波动模式相似。气体水平更显著的差异不是在物种之间，而是在居住在重土壤或轻土壤中的相邻种群之间：与相对较轻的土壤（红壤和黑色石灰土）相比，重土壤（粘土和玄武岩）中的氧气较低，二氧化碳较高。在雨季出现的气体浓度极值似乎随着隧道的部分水淹、动物挖掘活动以及由哺乳雌性及其后代居住的过度拥挤的繁殖丘而波动。不同土壤类型相邻地点的气体组成和土壤含水量表明，同一物种不同种群的低氧 - 高碳酸血症应激水平存在很大差异。越来越多与低氧应激相关的基因已被证明在地下东非鼹形鼠和地上大鼠（褐家鼠）之间表现出结构和功能差异，这可能反映了东非鼹形鼠在4000万年的进化过程中为在地下栖息地气体组成的剧烈波动中有效生存所经历的分子适应。
