Atop a towering Andean volcano measuring 6,739 meters, where the air is thin and temperatures hover below freezing, a minute leaf-eared mouse has established a habitat, feeding on poisonous plants. A global team, including scientists from McMaster University in Hamilton, Ont., has revealed some of the biological mechanisms enabling this phenomenon. Their research, published in the journal Science, indicates that high-altitude Andean leaf-eared mice possess enhanced heat generation capabilities in low-oxygen environments and have developed genetic adaptations to process toxic substances in their diet.
The species, known as Phyllotis vaccarum, has been identified on the summit of Volcán Llullaillaco, situated on the Chile-Argentina border. In this environment, oxygen levels are significantly lower compared to sea level. Grant McClelland, a co-author of the study and a biology professor at McMaster, expressed astonishment at the resilience of these mice, highlighting their ability to not only survive but thrive in such harsh conditions.
These mice hold the record for the widest elevation range among mammals, spanning from sea level along Chile’s northern coast to peaks exceeding 6,700 meters in the Andes. Researchers conducted genetic comparisons and laboratory tests on mice from various elevations, observing differences in heat production efficiency at simulated oxygen levels equivalent to sea level, 4,300 meters, and 7,000 meters. The highland mice exhibited superior heat generation capabilities compared to lowland counterparts, a crucial advantage in freezing climates where oxygen is scarce.
The highland mice leverage their muscle energy production and utilization mechanisms to withstand the cold temperatures at such elevations. Their mitochondria, responsible for converting oxygen and nutrients into energy, demonstrate a heightened capacity for energy production, particularly in shivering muscles—a key survival strategy in extreme cold. The abundance of mitochondria and their efficient use of lipid fuels provide a sustained energy source for shivering, essential for these mice in their challenging habitat.
Moreover, the study uncovered genetic adaptations in the mice related to detoxifying harmful compounds found in their limited diet on the high slopes. Despite the scarcity of edible vegetation, these mice have evolved mechanisms to process toxic plant materials, showcasing their remarkable ability to adapt to inhospitable environments. This research underscores the adaptability and resilience of life forms in extreme conditions, challenging traditional notions of where life can thrive.
McClelland emphasized the continuous surprises of evolution, illustrating how organisms can adapt and flourish in seemingly hostile environments. This study serves as a testament to the resilience and ingenuity of nature, showcasing the remarkable ability of these small mammals to not only survive but thrive at nearly 7,000 meters above sea level.