The influence of pheromones produced by freely growing laboratory populations on the reproductive maturation of prairie deermice following prenatal and postnatal exposure

Significantly more females reared on bedding soiled by different populations reproduced by 100 days of age than those reared on bedding soiled by the same populations (P<.1) or on clean bedding (P<.025) whereas the latter two groups did not differ significantly. Significantly greater percentages of females reproduced in both treatments maintained on soiled bedding than was true in the populations from which the bedding came. There were no significant differences between treatments in the weights of the reproductive organs (testes, seminal vesicles, ovaries, uteri) or in the numbers of corpora lutea or mature follicles in the ovaries of nulliparous females. The data suggest that if there were reproductively inhibiting pheromones influencing the population animals, they were altered or dissipated immediately after removal of the bedding from the population enclosures or that they were nonfunctional in the absence of the population animals. These data further suggest that the reproductive inhibition of population young is due to the presence of the populaton animals and that sociobiological factors within the populations act to prevent the reproductively stimulating influence of materials which may be present.     

The influence of urine from asymptotic laboratory populations on sexual maturation in prairie deermice

Male and female prairie deermice housed singly from weaning (21 days) until 40 days of age had urine from one of the following sources applied daily to their nostrils: sexually mature laboratory population males or females, and sexually mature breeder males or females from our laboratory colony. Other males and females were treated with water. Records were obtained of the weights of the tests, seminal vesicles and bacula of males and the ovaries and uteri of females at 40 days of age. The major results of this study were as follow: Female urine from sexually mature and inhibited population or isolated mice stimulated the development of the male reproductive organs significantly more than water or male urine. Male urine applied to young males did not differentially affect the weights of their reproductive organs compared with water and thus showed no inhibition effects. The reproductive organs of females treated with male urine did not differ significantly in weight from those of females treated with female urine. Females treated with water developed significantly larger uteri than those treated with urine from sexually mature population females (P≤0.02), inhibited population females (P<0.001) and inhibited population males (P<0.007).     

The influence of the social environment on sexual maturation of female deermice (Peromyscus maniculatus bairdi)

Population Ecology - Female deermice housed from weaning with groups of five females, five males or five males plus five females had significantly smaller uteri at 35–38 days of age compared...     

The effects of differential prenatal and postnatal social enviroments on sexual maturation of young prairie deermice (Peromyscus maniculatus bairdii).

We compared the influence of different social enviroments on sexual maturation of young prairie deermice. Between 12 and 48 hr after parturition, one-half of a litter from a population was exchanged with one-half of a litter from a bisexual pair. In each situation the remaining half-litter served as controls for the exchange procedure. The testes and vesicular weights of population-reared males were significantly larger than those of males reared by bisexual pairs, irrespective of prenatal enviroment. Generally, population-reared females also had larger reproductive organs than those reared by bisexual pairs, although these differences were not statistically significant. There were no significant differences in the adrenal weights of males or females, but females reared by bisexual pairs had larger absolute and relative adrenals than females reared in populations.     

Effects of grouping and fighting on the reproductive tracts of male white-footed mice (Peromyscus leucopus)

Summary Adult, male white-footed mice (Peromyscus leucopus) were subjected to a variety of social situations ranging from isolation during the 20 day experimental period to constant contact with both females and other adult males. Contacts included grouping (three or four males per cage) and exposure to fighters (once daily for 20 minutes). The following measurements were recorded: weights of the body, testes, epididymides, vesicular glands, vesicular gland tissue (wet and dry), seminal fluid of the vesicular gland, adrenal glands, and baculum; spermatozoan reserves of the testes and epididymides. Grouping significantly affected both the weight and spermatozoan reserves of the testes and epididymides, as well as both the tissue and seminal fluid weight of the vesicular glands. The results suggested a graded effect of all treatments on the reproductive tract. In order of magnitude of the associated response, from none to greatest, the treatments may be ranked as follows: pairing with females, isolating, handling, fighting, and grouping. All reproductive parameters measured showed this general ranking, suggesting that the response to the various treatments was similar and differed only quantitatively. The results further suggested decreased secretion of LH and testosterone, although measurements of testosterone did not substantiate this conclusion. The lack of significant effects of grouping on adrenal gland weights strengthened the argument that adrenal involvement is not a necessary adjunct to the suppression of the reproductive tract in groupedPeromyscus, but the adrenal may be involved if contacts between males result in overt fighting.