Comportement, croissance et influences maternelles et génétiques dans l'adaptation de la souris au froid

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Abstract
Long-term adaptation to cold, over 2 or more generations, was studied by breeding mice, Mus musculus, domestic and wild, in environments kept near or below 0.degree. C,. The changes imposed on females, by the combined action of cold and reproduction, include enlargement of the heart, liver and kidneys, and lengthening of the small intestine. Cold-adaptation of domestic mice results in lower body fat; but wild mice have little fat even in a warm environment. At birth, young of cold-adapted females have more fat than controls, and at 10 days they have more brown adipose tissue. The milk of both wild and domestic mice in a cold environment has a lower concentrations of sugars, but higher protein and fat, than that of controls. Effects of breeding wild mice in a cold environment include progressive changes over generatinos, such as higher growth rates and improved fertility on return to a warm environment. Differences between stocks bred at different temperatures are not only genetical. There are also maternal effects: cross-fostering experiments show the weight of yound at 3 wk to be influenced by the strain of the foster-grandparents. Phenotypic differences reflect the combined actions of genotype, ambient environment and maternal environment. Laboratory experiments provide hypotheses on which to base study of natural populations, but do not predict what will be found in them. Whild mice can evidently adapt to a given harsh environment by adopting one several alternative strategies.

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