Morphological and Physiological Responses to Altitude in Deer MicePeromyscus maniculatus

Abstract

Individuals within a species, living across a wide range of habitats, often display a great deal of phenotypic plasticity for organ mass and function. We investigated the extent to which changes in organ mass are variable, corresponding to environmental demand, across an altitudinal gradient. Are there changes in the mass of oxygen delivery organs (heart and lungs) and other central processing organs (gut, liver, kidney) associated with an increased sustainable metabolic rate that results from decreased ambient temperatures and decreased oxygen availability along an altitudinal gradient? We measured food intake, resting metabolic rate (RMR), and organ mass in captive deer mice (Peromyscus maniculatus bairdii) at three sites from 1,200 to 3,800 m above sea level to determine whether energy demand was correlated with organ mass. We found that food intake, gut mass, and cardiopulmonary organ mass increased in mice living at high altitudes. RMR was not correlated with organ mass differences along the altitudinal gradient. While the conditions in this study were by no means extreme, these results show that mice living at high altitudes have higher levels of energy demand and possess larger cardiopulmonary and digestive organs than mice living at lower altitudes.

The relationship between cardiopulmonary size and aerobic performance in adult deer mice at high altitude

“…This was unexpected because in repeated published and unpublished work we have observed an ~10% increase in hematocrit of high altitude-acclimated mice from this same colony (Hammond et al, 1999;Hammond et al, 2001;Hammond et al, 2002). Because blood draws on deer mice can have a significant impact on aerobic performance up to 2 weeks (Van Sant, 2012), we refrained from measuring hematocrit in HA animals while they were still at high altitude and waited until after their final normoxia run.…”

“…The change in whole-animal aerobic capacity resulting from acclimation to high altitude is accompanied by increased hematocrit, hemoglobin concentration and lung mass compared with animals acclimated to low altitude (Hammond et al, 1999;Hammond et al, 2001). Changes in splenic function have also been noted in response to high altitude acclimation, as it is generally considered to be associated with storage of red blood cells (Baker and Remington, 1960;Böning et al, 2011).…”

Regulatory changes contribute to the adaptive enhancement of thermogenic capacity in high-altitude deer mice

“…Because of this broad altitudinal distribution, deer mice have long been used as a model to study physiological mechanisms of acclimatization and adaptation to high-altitude hypoxia (3)(4)(5)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). The wellestablished connections between thermogenic capacity and fitness (3) make P. maniculatus an especially ideal study animal for investigating the mechanistic underpinnings of metabolic adaptation to high-altitude environments.…”

Age and Seasonal Aspects of Sexual Differences in Social Vole, Microtus socialis, (Rodentia, Arvicolinae), in the South of Ukraine

“…In most murine rodent species sexual differences, if detected, can be expressed in a bigger males size (Ralls, 1977Panteleev et al, 1990Markowski, Ostbye, 1992) or, conversely, females (Bank vole, 1981;Lammers et al, 2001). In some studies the differences were not registered at all (Hammond et al, 1999).…”

“…In murine rodents sexual differences of the majority morphological characters are slightly expressed (Panteleev et al, 1990;Meyer et al, 1996;Hammond et al, 1999) and often ignores in the practice of their comparative morphological studies. Meanwhile, the literature accumulated a lot of evidences of the specificity of sexual differences in different species (Kaneko, 1978;Grulich, 1987;Heske, Ostfeld, 1990;Boonstra et.…”