Effects of parity on pelvic size and shape dimorphism in Mus

Abstract

The pelvis is a sexually dimorphic structure and although the causes of that dimorphism have long been studied, relatively little is known regarding the effects of partuitive events on the magnitude of that dimorphism. Here, we use a sample of Mus musculus domesticus to contrast dimorphism in body length and os coxae size and shape between males and parous and nulliparous females. We also test for correlations between relative litter size (L/M) and relative offspring size (O/M) with body length and os coxae size and shape in parous females. Males had greater body length than nulliparous females but were not different from parous females. Females as a whole had the largest os coxae, with parous females having the largest and males the smallest. Os coxae shape was also significantly different between groups and was most divergent between parous females and males than between nulliparous females and males. Os coxae shape differences between females are associated with differences in body length between females and O/M is correlated with os coxae shape in parous females such that females with the largest offspring have the most divergent shapes along the relative warp one axis. Pelvic shape differences between males and females were consistent with previous findings in other taxa which identify the pubo-ischial complex as the primary region of dimorphism.

Sacro-femoral-pubic angle: a coronal parameter to estimate pelvic tilt

“…Patriquin et al [18] demonstrated that pubic bone and sciatic notch morphology differed between the genders enough to reliably predict gender based on pelvic shape alone. Schutz [19] recently discussed the role of parity on pelvic remodeling. In summary, both congenital and environmental factors may explain variations in correlation noted in this investigation.…”

Developmental evidence for obstetric adaptation of the human female pelvis

“…Although our data show that female and male trajectories diverge substantially before the attainment of sexual maturity, we further assessed whether maternity (pregnancy and lactation) has an influence on the development of pelvic shape, as reported, for example, in mice (41). To this end, we analyzed pelvic shape variation in a subsample of females with known maternity status.…”

Sexual dimorphism, asymmetry, and the effect of reproduction on pelvis bone in the bank vole, Myodes glareolus

“…We also found that the differences in bone size of the pelvis occur not only between females and males but also between nulliparous and parous females. Parturition may affect the size of various skeletal elements Miller 1999, 2001;Johanson and Berger 2003;Specker and Binkley 2005), but relatively little is known about the effects of parturition event on the pelvis dimorphism in small mammals (Schutz et al 2009b). Our study showed that parous females revealed more profound differences in pubic size from males than nulliparous females.…”

“…It is thought that pelvic dimorphism may emerge also from functional pressures on the pelvis produced by weight bearing, locomotion, and parturition (Schutz et al 2009b). Weight bearing affects the shape of the pelvis due to the pressures of weight to the rear limb.…”

“…Pelvic dimorphism is primarily genetically determined and grows in response to sex hormones during puberty (Schutz et al 2009b). It is thought that pelvic dimorphism may emerge also from functional pressures on the pelvis produced by weight bearing, locomotion, and parturition (Schutz et al 2009b).…”