Litter sex composition affects life-history traits in yellow-bellied marmots.
ABSTRACT 1. The presence of siblings might have long-lasting fitness consequences because they influence the early environment in which an animal develops. Several studies under laboratory conditions have shown long-lasting consequences from the presence of male siblings in utero on morphology and life-history traits. However, in wild animals, such effects of litter sex composition are unexplored. 2. We capitalized on a long-term study of individually marked yellow-bellied marmots (Marmota flaviventris) and documented the effects of weaned litter sex composition and anogenital distance on several life-history and fitness traits. 3. First, we demonstrated that the number of males in a litter influenced anogenital distance. Then, we found that masculinized females, those with larger anogenital distances, were less likely to survive their first hibernation, were more likely to disperse and were less likely to become pregnant and wean young. Males from male-biased litters had lower growth rates, but we failed to detect longer-term consequences. 4. Taken together, our results show profound sex-dependent effects of litter sex composition, probably due to differential prenatal exposure to androgens, in free-living animals. We conclude that masculinization might constitute an alternative mechanism explaining variation in different demographic traits. This finding highlights the importance of studying these maternal effects, and they enhance our concern over the widespread use of endocrine disrupting compounds.
Article: Anogenital distance is related to ovarian follicular number in young Spanish women: a cross-sectional study.[show abstract] [hide abstract]
ABSTRACT: BACKGROUND: In animals, anogenital distance (AGD) at birth reflects androgen levels during pregnancy and predicts adult AGD. Little is known about AGD in relation to female reproductive characteristics in humans, a question this study was designed to explore. METHODS: We used multiple linear and logistic regression analyses to model the relationships between adult female reproductive system characteristics (e.g. ovarian morphology, menstrual cycle) and two measures of AGD [anus-fourchette (AGDAF) and anus-clitoris (AGDAC)] in 100 college-age volunteers in Spain. Ovarian morphology was classified as having < 6 or >= 6 follicles per ovary. RESULTS: Both AGD measures were positively associated with ovarian follicle number, with AGDAF being more strongly associated. Women in the upper tertile of the AGDAF and AGDAC distributions were more likely to have >= 6 ovarian follicles [OR: 6.0 (95% CI 2.0, 17.6) and 3.0 (95% CI 1.1, 8.6), respectively] compared to women in the lowest tertile. CONCLUSIONS: Increased follicular recruitment has been related to excess androgen exposure in utero in toxicological studies. Our results suggest that the androgenic environment during early fetal life may influence reproductive system development, including AGD, in human females.Environmental Health 12/2012; 11(1):90. · 2.65 Impact Factor