Periconceptional influences on offspring sex ratio and placental responses

2012 ◽  
Vol 24 (1) ◽  
pp. 45 ◽  
Author(s):  
Cheryl S. Rosenfeld

Maternal diet and secondary factors can strikingly influence fetal outcomes, including biasing offspring sex ratio and altering the molecular biological responses of the conceptus, namely within the placenta. Alterations in the in utero environment might also lead to profound developmental origin of health and disease (DOHaD) outcomes into adulthood, including increased risk for cardiovascular disease, obesity and cancer, with males in general being at greater risk for these diseases. Female mice maintained on a very high fat (VHF) diet birth more sons than those on a chow-based and low fat (LF), high carbohydrate diet, with the latter group producing more daughters. However, neither the underlying mechanisms that contribute to this shift in offspring sex ratio nor when they occur during pregnancy have been resolved. In this review, we consider the evidence that maternal diet and other factors influence secondary sex ratio in a variety of species, including humans, and discuss when this skewing might occur. Additionally, we examine how fetal sex and maternal diet influences gene expression patterns in the mouse placenta, which serves as the primary nutrient acquisition and communication organ between the mother and her developing pups. These adaptations to diet observed as changes in gene expression are likely to provide insight into how the placenta buffers the fetus proper from environmental shifts in nutrient availability during pregnancy and whether male and female conceptuses respond differently to such challenges.

2018 ◽  
Vol 285 (1891) ◽  
pp. 20181251 ◽  
Author(s):  
Andrea E. Wishart ◽  
Cory T. Williams ◽  
Andrew G. McAdam ◽  
Stan Boutin ◽  
Ben Dantzer ◽  
...  

Fisher's principle explains that population sex ratio in sexually reproducing organisms is maintained at 1 : 1 owing to negative frequency-dependent selection, such that individuals of the rare sex realize greater reproductive opportunity than individuals of the more common sex until equilibrium is reached. If biasing offspring sex ratio towards the rare sex is adaptive, individuals that do so should have more grandoffspring. In a wild population of North American red squirrels ( Tamiasciurus hudsonicus ) that experiences fluctuations in resource abundance and population density, we show that overall across 26 years, the secondary sex ratio was 1 : 1; however, stretches of years during which adult sex ratio was biased did not yield offspring sex ratios biased towards the rare sex. Females that had litters biased towards the rare sex did not have more grandoffspring. Critically, the adult sex ratio was not temporally autocorrelated across years, thus the population sex ratio experienced by parents was independent of the population sex ratio experienced by their offspring at their primiparity. Expected fitness benefits of biasing offspring sex ratio may be masked or negated by fluctuating environments across years, which limit the predictive value of the current sex ratio.


2004 ◽  
Vol 71 (4) ◽  
pp. 1063-1070 ◽  
Author(s):  
Cheryl S. Rosenfeld ◽  
R. Michael Roberts

2016 ◽  
Vol 9 (3) ◽  
pp. 131-138 ◽  
Author(s):  
A.E. Gam ◽  
K.J. Navara

Previous research suggests that environmental and social factors can drive female birds to bias offspring sex ratios. The underlying mechanisms controlling these adjustments remain unclear. Results from experimental and correlative research suggest that maternal corticosterone plays an important role in this process. Since females are the heterogametic sex in birds, corticosterone may potentially bias offspring sex ratios during meiotic segregation, through non-random segregation of sex chromosomes. In a previous study, we showed that pharmacological elevations of corticosterone near the time of meiotic segregation exerted an effect on offspring sex ratio, causing female Zebra Finches ( Taeniopygia guttata) to produce significantly more males. Here, we aimed to determine whether endogenous elevations in the physiological range have similar effects on offspring sex. First we examined offspring sex ratio in relation to baseline corticosterone levels to determine if natural variation in circulating corticosterone near the time of meiotic segregation is related to offspring sex ratio. Next, we used a 5-minute bag handling protocol to induce corticosterone elevations 5 hours prior to ovulation. Maternal baseline corticosterone levels did not correlate with average clutch sex ratios. In addition, the sex ratios produced by females exposed to handling stress did not differ from sex ratios produced by unmanipulated females. Together these results suggest that physiological levels of endogenous corticosterone, both baseline and acutely elevated near the time of sex determination may not be involved in the adjustment of primary sex ratios in Zebra Finches.


Behaviour ◽  
2009 ◽  
Vol 146 (11) ◽  
pp. 1513-1529 ◽  
Author(s):  
Nikolaus Von Engelhardt ◽  
Sylvia Kaiser ◽  
Norbert Sachser ◽  
Kristina Kemme ◽  
Ton Groothuis ◽  
...  

AbstractEvolutionary theory suggests that offspring sex should be adjusted to environmental conditions in order to maximize future reproductive success. In several animal taxa environmental factors indeed affect the secondary sex ratio. In humans, changes in the sex ratio at birth have been associated with population stressors like war, environmental disasters or economic strife during pregnancy. Here we compared litter sex ratios of female guinea pigs, exposed experimentally to a stable and an unstable social environment. In the latter group composition was changed every three days. Under unstable social conditions the sex ratio was significantly more biased towards daughters than in the stable social situation. This finding was consistent among four independent experiments, conducted independently from each other. Life expectancy can be dramatically reduced under conditions of social instability. Hence mothers in such conditions should bias their investment towards the sex that reaches sexual maturity first, which is the female sex in this species. Thus, to shift the offspring sex ratio towards more daughters under conditions of social instability may represent a maternal strategy to maximize future reproductive success.


2016 ◽  
Vol 283 (1841) ◽  
pp. 20161206 ◽  
Author(s):  
Bao-Jun Sun ◽  
Teng Li ◽  
Yi Mu ◽  
Jessica K. McGlashan ◽  
Arthur Georges ◽  
...  

The adaptive significance of temperature-dependent sex determination (TSD) has attracted a great deal of research, but the underlying mechanisms by which temperature determines the sex of a developing embryo remain poorly understood. Here, we manipulated the level of a thyroid hormone (TH), triiodothyronine (T 3 ), during embryonic development (by adding excess T 3 to the eggs of the red-eared slider turtle Trachemys scripta , a reptile with TSD), to test two competing hypotheses on the proximate basis for TSD: the developmental rate hypothesis versus the hormone hypothesis . Exogenous TH accelerated embryonic heart rate (and hence metabolic rate), developmental rate, and rates of early post-hatching growth. More importantly, hyperthyroid conditions depressed expression of Cyp19a1 (the gene encoding for aromatase) and levels of oestradiol, and induced more male offspring. This result is contrary to the direction of sex-ratio shift predicted by the developmental rate hypothesis , but consistent with that predicted by the hormone hypothesis . Our results suggest an important role for THs in regulating sex steroid hormones, and therefore, in affecting gonadal sex differentiation in TSD reptiles. Our study has implications for the conservation of TSD reptiles in the context of global change because environmental contaminants may disrupt the activity of THs, and thereby affect offspring sex in TSD reptiles.


2004 ◽  
Vol 10 (1) ◽  
pp. 51-57 ◽  
Author(s):  
Bernt-Erik Sæther ◽  
Erling J. Solberg ◽  
Morten Heim ◽  
John E. Stacy ◽  
Kjetill S. Jakobsen ◽  
...  

2011 ◽  
Vol 45 (1) ◽  
pp. 55-57 ◽  
Author(s):  
M O M Chelini ◽  
N L Souza ◽  
E Otta

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