Transgenerational sex determination: the embryonic environment experienced by a male affects offspring sex ratio.
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ABSTRACT:
SUBMITTER: Warner DA
PROVIDER: S-EPMC3776964 | biostudies-other | 2013
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict.
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Project description: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 (T3), during embryonic development (by adding excess T3 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.
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Project description:Evolutionary models of sex ratio adjustment applied to mammals have ignored that females may gain indirect genetic benefits from their mates. The differential allocation hypothesis (DAH) predicts that females bias the sex ratio of their offspring towards (more costly) males when breeding with an attractive male. We manipulated the number of available males during rut in a polygynous ungulate species, the reindeer (Rangifer tarandus), and found that a doubling of average male mass (and thus male attractiveness) in the breeding herd increased the proportion of male offspring from approximately 40 to 60%. Paternity analysis revealed indeed that males of high phenotypic quality sired more males, consistent with the DAH. This insight has consequences for proper management of large mammal populations. Our study suggests that harvesting, by generating a high proportion of young, small and unattractive mates, affects the secondary sex ratio due to differential allocation effects in females. Sustainable management needs to consider not only the direct demographic changes due to harvest mortality and selection, but also the components related to behavioural ecology and opportunities for female choice.
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Project description:Sex allocation theory predicts that when sons and daughters have different reproductive values, parents should adjust offspring sex ratio towards the sex with the higher fitness return. Haplo-diploid species directly control offspring sex ratio, but species with chromosomal sex determination (CSD) were presumed to be constrained by Mendelian segregation. There is now increasing evidence that CSD species can adjust sex ratio strategically, but the underlying mechanism is not well understood. One hypothesis states that adaptive control is more likely to evolve in the heterogametic sex through a bias in gamete production. We investigated this hypothesis in males as the heterogametic sex in two social spider species that consistently show adaptive female-biased sex ratio and in one subsocial species that is characterized by equal sex ratio. We quantified the production of male (0) and female (X) determining sperm cells using flow cytometry, and show that males of social species produce significantly more X-carrying sperm than 0-sperm, on average 70%. This is consistent with the production of more daughters. Males of the subsocial species produced a significantly lower bias of 54% X-carrying sperm. We also investigated whether inter-genomic conflict between hosts and their endosymbionts may explain female bias. Next generation sequencing showed that five common genera of bacterial endosymbionts known to affect sex ratio are largely absent, ruling out that endosymbiont bacteria bias sex ratio in social spiders. Our study provides evidence for paternal control over sex allocation through biased gamete production as a mechanism by which the heterogametic sex in CSD species adaptively adjust offspring sex ratio.
| S-EPMC5897641 | biostudies-literature
Project description:A major component of sex-allocation theory, the Trivers-Willard model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex-by-environment effects is mixed, and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex-by-environment effect on offspring using two experiments, one in which we manipulated age differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted, females with high investment ability overproduced sons relative to those with lower ability. Males were also overproduced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling-competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions. Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed-sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that parents are able to produce. Offspring sex interacts with the neonatal environment to influence offspring fitness, thus favouring sex-ratio adjustment by parents. However, increased sensitivity of males to environmental conditions, such as sibling rivalry and resource availability, reduces the fitness returns from highly male-biased broods.
| S-EPMC4377307 | biostudies-literature
Project description:In this study, I predict that the global variation of offspring sex ratio might be influenced in part by the level of parasite stress. From an energetic standpoint, higher gestational costs of producing a male offspring could decrease male births in a population with limited resources. This implies that, any factor that limits the parental resources could be expected to favor female offspring production. Human sex ratio at birth (SRB) is believed to be influenced by numerous socioeconomic, biological, and environmental factors. Here, I test a prediction that parasite stress, by virtue of its effects on the general health condition, may limit the parental investment ability and therefore could influence the SRB at the population level. The statistical analysis supports this prediction, and show that the level of parasite stress has a significant inverse relation with population SRB across the world. Further, this relation is many-folds stronger than the association of SRB with other factors, like; polygyny, fertility, latitude, and son-preference. Hence, I propose that condition affecting ability of parasites (but not adaptive significance) could be a likely causal basis for the striking variation of SRB across populations.
| S-EPMC3458865 | biostudies-literature
Project description:ObjectiveIn mammals, high parental testosterone levels present around the time of conception are thought to skew offspring sex ratio toward sons. The second to fourth digit ratio (digit ratio) is now widely accepted as a negative correlate of prenatal testosterone. Thus, we investigated the association between digit ratio and offspring sex ratio.MethodsA total of 508 Korean patients (257 males and 251 females) less than 60 years old who had one or more offspring were prospectively enrolled. The lengths of the 2nd and 4th digits of the right hand were measured by a single investigator using a digital vernier calliper. Next, the patients' lifetime offspring birth sex ratios were investigated.ResultsMaternal (rather than paternal) digit ratio was significantly associated with the number of sons (r = -0.153, p = 0.015), number of daughters (r = 0.130, p = 0.039), and offspring sex ratio (r = -0.171, p = 0.007). And, the maternal digit ratio was a significant factor for predicting offspring sex ratio (B = -1.620, p = 0.008) on multiple linear regression analysis. The female patients with a lower digit ratio (< 0.95) were found to have a higher offspring sex ratio (0.609 versus 0.521, p = 0.046) compared to those with a higher digit ratio (? 0.95). Furthermore, females in the low digit ratio group have a probability 1.138 greater of having sons than females in the high digit ratio group.ConclusionsMaternal digit ratio was negatively associated with offspring sex ratio. Females with a lower digit ratio were more likely to have more male offspring compared to those with a higher digit ratio. Thus, our results suggest that the sex of offspring might be more influenced by maternal rather than paternal factors.
| S-EPMC4648576 | biostudies-literature
Project description:BackgroundExposure to occupational radiation can lower the male sex ratio. However, specific radiation exposure to the testes has not been evaluated.ObjectiveThis study aimed to examine the association between testicular radiation exposure and lower male sex ratio in children.MethodsA comprehensive questionnaire survey was administered to 62 full-time male doctors with children aged < 10 years at 5 hospitals. Based on the possibility of testicular radiation exposure 1 year before the child's birth, participants were assigned to 3 groups as follows: RT (orthopedic surgery), RNT (cardiology/neurosurgery), and N (others). Intergroup differences in the proportion of female children were ascertained, and the female sex ratio (number of female/total number) of each group was compared against the standard value of 0.486. Multivariate logistic regression analysis with a generalized estimating equation was used to model the effects on the probability of female birth while controlling for the correlation among the same fathers.ResultsThe study population included 62 fathers and 109 children, 49 were female: 19/27, 11/30, and 19/52 in the RT, RNT, and N group, respectively; the RT group had the highest proportion of females (p = 0.009). The p values for comparisons with the standard sex ratio (0.486) were 0.02, 0.19, and 0.08 for the RT, RNT, and N groups, respectively. Based on the N group, the adjusted odds ratios for the child to be female were 4.40 (95% confidence interval 1.60-2.48) and 1.03 (0.40-2.61) for the RT and RNT groups, respectively.ConclusionsOur results imply an association between testicular radiation exposure and low male sex ratio of offspring. Confirmatory evidence is needed from larger studies which measure the pre-conceptional doses accumulated in various temporal periods, separating out spermatogonial and spermatid effects.
| S-EPMC8719764 | biostudies-literature
Project description:Dietary polyunsaturated fatty acids (PUFAs) can influence fertility in farm animals. Some evidence in mice and sheep have suggested that PUFAs may influence offspring sex ratio, which may have significant value for cattle production. To test this hypothesis, three groups of Holstein cows were supplemented with either 0%, 3% or 5% protected fat (PF) in the form of calcium salt of fatty acids (rich in omega-6) from 14-21 days pre-partum until conception. Proven-fertile frozen semen from the same ejaculate was used for insemination. Calf sex recorded at birth was 8/19 (42.1%) male offspring in the control group, increasing to 14/20 (70%, P > 0.05) and 17/20 (85%, P < 0.05) in 3% and 5% PF, respectively. To test if this effect was caused by a direct influence on the oocyte, we supplemented bovine cumulus oocyte complexes during in vitro maturation with either omega-3 alpha-linolenic acid (ALA), omega-6 linoleic acid (LA) or trans-10, cis-12 conjugated linoleic acid (CLA). Sex ratio of the produced transferable embryos was determined using PCR of SRY gene. Similar to the in vivo results, sex ratio was skewed to the male side in the embryos derived from LA- and CLA-treated oocytes (79% and 71%) compared to control and ALA-treated oocytes (44% and 54%, respectively). These results indicate that both dietary and in vitro supplementation of omega-6 PUFAs can skew the sex ratio towards the male side in cattle. Further experiments are required to confirm this effect on a larger scale and to study the mechanisms of action that might be involved.
| S-EPMC6161865 | biostudies-literature
Project description:Transgenerational effects of early experience on behavioural, hormonal and gene expression responses to acute stress in the precocial chicken. The data for the parental stressed and control birds is available in ArrayExpress with accession E-MTAB-924, while this experiment only concerns their offspring that never been exposed to early life stress.
2012-01-02 | E-MTAB-925 | biostudies-arrayexpress