The Effects of Temperature on the Onset of Puberty

Abstract

The reproduction of laboratory mice (Mus musculus) kept at low environmental temperatures has been studied in very great detail by Barnett and his co-workers in Glasgow, and this work can be traced through the bibliographies in the papers by Barnett and Coleman (1959) and Barnett (1962). Mice were maintained at −3° C and their reproduction compared with mice kept at 21° C as controls. At the colder temperature the mean age of vaginal opening was 33 days (controls at 26 days), but the first oestrous smear in the cooled mice was seen on average at 61 days, compared with 38 days for the control. The vaginal openings in both groups occurred at the same body weight of 13 g, so that the temperature reduction had a marked effect in reducing the rate of growth of the female mice. A similar effect was also noted in mice with an ancestry of several generations in the cold. Barnett suggested that the slowing down of puberty may be attributed to the prior demands for catabolism but could not account for the reproductive patterns of 21° C females placed under −3° C temperatures, which first altered to the −3° C pattern but then reverted to their original pattern. There can be little doubt, however, that the delay in reproductive maturity in experiments such as this must be related very closely to the reduced rate of growth, and should therefore be considered as a secondary phenomenon. It is also possible that the selection of −3° C as the lower temperature, one considerably lower than normally met with by wild housemice, has unduly emphasized the effect. Knudsen (1962) was unable to find any difference in the age of puberty in groups of mice kept at 18°, 25°, and 32° C.