Sex and Intrauterine Position Influence the Size of the Gerbil Hippocampus
Section snippets
Subjects
Twenty-six male and 26 female Mongolian gerbils born and reared in the vivarium of the McMaster University Department of Psychology served as subjects. All were second or third generation descendants of breeding stock acquired from Tumblebrook Farms (Brookfield, MA). Seventeen male and 16 female subjects were delivered by cesarian section. The remaining 19 subjects (9 males and 10 females), referred to below as group R, were randomly selected from among males and females used as breeding stock
RESULTS
Volume of the hippocampus and telecephalon for all males and females is shown in Fig. 1. Analysis of covariance was used to examine the effects of sex and intrauterine position on the size of the hippocampus, using size of the telencephalon as a covariate. Homogeneity of the regression of hippocampal volume on telencephalon volume was confirmed for both sexes and for the three intrauterine conditions (2M, 2F, and R) prior to analysis of covariance. Mean residuals from this regression are shown
DISCUSSION
The results provide evidence for a sex difference in relative hippocampal size in a random selection of Mongolian gerbils in the direction expected on the basis of sex differences in home range size in the wild. Like male meadow voles and kangaroo rats 15, 16, male gerbils have a larger home range and a relatively larger hippocampus than do females.
As can be seen most clearly in Fig. 2, gestation in either 2F or 2M intrauterine positions eliminated the sex difference found in randomly selected
Acknowledgements
This research was supported by grants from the Natural Sciences and Engineering Research Council of Canada to D.F.S. and M.M.C. We would like to thank Tammi Ivanco, Karen-Anne Moore, and Miney Ham for assistance in preparing gerbil brains, Richard Cooley for expert histological work, and Mark Sangster for digitizing several thousand brain sections. Elizabeth Hampson and Scott Moffat provided valuable comment and discussion.
References (24)
- et al.
Ecology and social behaviour of Mongolian gerbils, Meriones unguiculatus, at Xilinhot, Inner Mongolia, China
Anim. Behav.
(1989) - et al.
Concentrations of sex steroid hormones in pregnant and fetal Mongolian gerbils
Physiol. Behav.
(1991) - et al.
Effects of uterine position on rate of sexual development in female Mongolian gerbils
Physiol. Behav.
(1988) - et al.
Fetal uterine position affects copulation and scent marking by adult male gerbils
Physiol. Behav.
(1990) - et al.
Sexually dimorphic spatial learning varies seasonally in two populations of deer mice
Brain Res.
(1994) - et al.
Performance (re-acquisition) of a water-maze task by adult meadow voles: effects of age of initial task acquisition and in utero environment (litter sex-ratio)
Behav. Brain Res.
(1994) - et al.
Sexual selection for spatial-learning ability
Anim. Behav.
(1989) - et al.
Is testosterone related to spatial cognition and hand preference in humans?
Brain Cognit.
(1994) - et al.
Resolving a mystery: progress in understanding the function of adrenal steroid receptors in hippocampus
Progr. Brain Res.
(1994) The dentate gyrus is sexually dimorphic in prepubescent rats: testosterone plays a significant role
Brain Res.
(1993)
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