On top of a 6,739-meter Andean volcano, where the air is thin and temperatures remain consistently freezing, a small leaf-eared mouse has adapted to survive by consuming toxic plants. An international research team, which included scientists from McMaster University in Hamilton, Ontario, has unveiled the biological mechanisms behind this remarkable feat. The study, recently published in the journal Science, reveals that high-altitude Andean leaf-eared mice possess the ability to generate heat more efficiently in low-oxygen environments. Genetic analysis suggests they have evolved to metabolize harmful compounds found in their food.
The species, known as Phyllotis vaccarum, has been discovered at the summit of Volcán Llullaillaco on the border of Chile and Argentina. At such elevations, the oxygen levels are significantly reduced, posing a challenge for survival. Grant McClelland, a co-author of the study and a biology professor at McMaster, expressed astonishment at the resilience of these mice in such harsh conditions.
These mice have the widest known range of altitudes among mammals, inhabiting both sea level areas along Chile’s northern coast and peaks exceeding 6,700 meters in the Andes. Researchers conducted experiments comparing the genetic makeup and heat production of mice from various altitudes. They found that highland mice are better equipped to maintain heat production in low-oxygen settings compared to their lowland counterparts, providing a crucial advantage in cold climates.
The muscular structure of highland mice supports efficient energy production and usage, essential for activities like shivering to maintain body temperature. Mitochondria in their muscles exhibit a higher capacity to convert oxygen and nutrients into energy compared to lowland mice. This advantage is crucial for utilizing lipid fuels for sustained energy during shivering.
Additionally, genetic analysis revealed adaptations in detoxifying genes in highland mice, enabling them to process toxic compounds found in their limited diet at high altitudes. The ability of these small mammals to thrive near 7,000 meters serves as a testament to the adaptability of life forms in extreme environments. McClelland emphasized that evolutionary surprises continue to challenge biologists, showcasing life’s resilience in seemingly inhospitable conditions.