Differences in the sex ratios of offspring originating in the right and left ovaries of Mongolian gerbils (Meriones unguiculatus)

Abstract

Two experiments were undertaken to investigate the cause of the observed tendency of Mongolian gerbil dams to gestate more male than female fetuses in their right uterine horns and more female than male fetuses in their left uterine horns. It was found in Expt 1 that female gerbils that had both ovaries removed and portions of their right ovary placed in both ovarian capsules gestated significantly more male fetuses than did females that had both ovaries removed and portions of their left ovaries placed in both ovarian capsules. Expt 2 showed that female gerbils that had both their ovaries removed and then returned to their original locations gestated more males in their right uterine horns than in their left, while females that had the positions of their ovaries exchanged gestated more male fetuses in their left uterine horns than in their right. The data were consistent with the hypothesis that lateral asymmetries in gerbil ovaries rather than in gerbil uterine horns cause partial uterine segregation of gerbil fetuses by sex.

Sex Ratio of Bovine Embryos and Calves Originating from the Left and Right Ovaries1

“…Although Clark et al [11] used different experimental methods in the gerbil, the similar results reported reinforce the conclusions presented in this study. The data of the present experiments, in combination with the results reported by Clark et al [11], suggest that there is no preferential selection for embryos of a single sex in the uterine horns of recipient cattle.…”

“…In addition, the sexually dimorphic developmental inequalities previously reported were encountered in these experiments. Similarly, these data compare favorably with laterally asymmetric sex ratio distributions reported in the rabbit [1], mouse [2,36], and Mongolian gerbil [11,30,37] and those detected in the other experiments of this study. However, the mechanism underlying the difference in the sex ratio distortion found in IVF-derived embryos generated in oocytes from the left but not from the right ovary remains unknown.…”

“…The data of the present experiments, in combination with the results reported by Clark et al [11], suggest that there is no preferential selection for embryos of a single sex in the uterine horns of recipient cattle. Moreover, the sex ratio of embryos and calves produced by natural mating, superovulated cows, and ET suggests that the ovary of origin from which the pregnancy is derived, rather than the uterine horn of gestation, may influence the sex of offspring in cattle.…”

“…In an effort to determine the source of the uterine horn sex ratio variation, Clark et al [11] surgically translocated the left and right ovaries within Mongolian gerbil females. These authors reported an inversion of the sex ratio (% male) within the uterine horns of the treated animals, with more females on the right and males on the left, and postulated that the ovary of origin, rather than the horn of gestation, was responsible for the skewed ratio.…”

Long-Lasting Fitness Consequences of Prenatal Sex Ratio in a Viviparous Lizard

“…In some rodents, males and females are separated into different uterine horns (Clark and Galef 1990;Clark et al 1991Clark et al , 1994, possibly to reduce steroid leakage between the sexes (although other explanations are possible, for example that differential production of male and female eggs by the ovaries facilitates differential sex allocation; Clark et al 1994). No such redistribution of offspring between oviducts is evident in L. vivipara (T. Uller, unpubl.…”