Physiological and morphological responses to simultaneous cold exposure and parasite infection by wild‐derived house mice

Summary1 Many animals respond to environmental demands with phenotypic plasticity of morphology and physiology. We examined the effects of ambient temperature and parasitism on morphology and physiology of wild‐derived house mice ( Mus musculus ) that were exposed to cold and/or experimentally infected with a naturally occurring intestinal nematode ( Heligmosomoides polygyrus ). 2 Parasitized mice had changes in some organ masses, decreased ability to digest food, and lower rates of glucose transport but similar total glucose transport capacity as unparasitized mice. Wild‐derived house mice did not use fat stores to respond to parasitism but did increase mucosal mass in the small intestine enough to maintain glucose acquisition at a similar level to unparasitized mice. 3 Cold‐exposed mice showed increased masses of some organs, lower rates of glucose transport but similar total capacity to transport glucose as warm acclimated mice. 4 The effects of cold exposure and parasite infection were largely independent of each other for the morphological and physiological parameters we measured. 5 The more recent exposure of wild‐derived house mice to fluctuating temperatures and to parasite infection may help to explain the subtle differences that we observed in how wild‐derived mice respond to environmental demands compared to their laboratory mouse counterparts.