The effect of sex hormones on sex inversion in the mussel Mytilusgalloprovincialis.

Global changes in the coastal ecosystems of oceans and seas, influenced by natural environmental factors and anthropogenic load, have led to a shift in the sexual structure of the mussel Mytilus galloprovincialis, a species cultivated in many countries. This paper is the first to study the effects of steroid hormones on sex inversion and mortality in the M. galloprovincialis. A unidirectional pattern of sex change from females to males was observed. A 100% sex change of females was achieved under the influence of the hormone testosterone during the period of post-spring restructuring of the gonads. No sex change occurred when males and females were exposed to 17ß-estradiol. The mortality of mollusks did not exceed 5%.

Induced abortion after advent of fetal sex detection technology and child sex at birth.

BACKGROUND: National level Sex Ratio at Birth (SRB) is normal in Bangladesh despite its patriarchal social structures, strong son preference, and low fertility level, widely recognized as preconditions for Gender-Biased Sex Selection (GBSS). To better understand this anomaly, we examine the trend in SRB in a sub-district in Bangladesh and assess the impact of the introduction of fetal sex-detection technology and the history of induced abortion on child sex using longitudinal data. METHODS: We have used secondary data collected routinely by icddr, b's Matlab Health and Demographic Surveillance System (HDSS) between 1982 and 2018. All births occurring during this period (N = 206,390) were included in the analyses. We calculated the SRB and used multivariate logistic regression analyses to assess the likelihood of birth of a male child before and after the introduction of ultrasonogram in Matlab. RESULTS: Overall, SRB was within the natural limit (106) during 1982-2018 in Matlab. SRB among women with a history of induced abortion was 109.3 before the introduction of ultrasonography in 2001 and 113.5 - after 2001. Women's history of induced abortion prior to introduction of ultrasonogram (1982-2000) increased the likelihood of birth of a male child 1.06 times (AOR 1.06; 95% CI- 1.01-1.11). In the period after, however, this likelihood was 1.08 (AOR 1.08; 95% CI- 1.02-1.15). CONCLUSIONS: In a context with normal SRB, it was found to be skewed among women who had induced abortion. SRB was relatively more skewed among such women after the advent of ultrasonogram compared to a period without ultrasonogram. Moreover, induced abortion after introduction of fetal sex determination technology increased the likelihood of birth of a male child. These findings suggest the plausibility of GBSS in a sub-group. Further research is needed, particularly in regions with skewed SRB to examine whether GBSS is indeed a threat to Bangladesh.

Autosomal suppression of sex-ratio meiotic drive influences the dynamics of X and Y chromosome coevolution.

Sex-ratio meiotic drivers are selfish genes or gene complexes that bias the transmission of sex chromosomes resulting in skewed sex ratios. Existing theoretical models have suggested the maintenance of a four-chromosome equilibrium (with driving and standard X and suppressing and susceptible Y) in a cyclic dynamic, studies of natural populations have failed to capture this pattern. Although there are several plausible explanations for this lack of cycling, interference from autosomal suppressors has not been studied using a theoretical population genetic framework even though autosomal suppressors and Y-linked suppressors coexist in natural populations of some species. In this study, we use a simulation-based approach to investigate the influence of autosomal suppressors on the cycling of sex chromosomes. Our findings demonstrate that the presence of an autosomal suppressor can hinder the invasion of a Y-linked suppressor under some parameter space, thereby impeding the cyclic dynamics, or even the invasion of Y-linked suppression. Even when a Y-linked suppressor invades, the presence of an autosomal suppressor can prevent cycling. Our study demonstrates the potential role of autosomal suppressors in preventing sex chromosome cycling and provides insights into the conditions and consequences of maintaining both Y-linked and autosomal suppressors.

Spatio-temporal metapopulation trends: The coconut crabs of Zanzibar.

Species experience a variety of environmental and anthropogenic conditions across their ranges leading to spatial variation in population dynamics. Understanding population dynamics under different conditions is important but it is challenging to allocate limited effort to spatial and temporal subpopulation monitoring. Using GLMMs, we analyze survey data of a metapopulation of coconut crabs spanning 7 years and 15 sites in and near the Pemba archipelago, Zanzibar, to estimate trends in population size (based on catch per unit effort), weight and sex ratio at the meta- and subpopulation level and investigate anthropogenic drivers of these trends. We found that the overall metapopulation has remained stable in terms of size and composition over the survey period, but observed diverging trends in population size and sex ratio at some subpopulations. Formal protection of sites was associated with positive population trends. Of nine sites for which we could estimate site-specific trends, three showed increasing and two decreasing trends, whereas four sites had stable subpopulations. Although anthropogenic factors affected the average weight, and the incidence of small and large individuals, we found no temporal trends in any weight-related measures. Furthermore, there were no apparent patterns between weight-related measures and subpopulation trends. The metapopulation was biased toward males, and exploitation appeared to be associated with declining trends in the proportion of females, likely an artifact of a strong decline in the proportion of females in one of only two exploited sites in the dataset. Educational campaigns implemented in 2020 at six sites were not related to higher population sizes in later surveys. The variable trends in subpopulation sizes and composition highlight the need for spatially replicated monitoring in metapopulations. The analyses further provide a detailed baseline for future subpopulation studies of this vulnerable species in one of its last remaining metapopulations in the Western Indian Ocean.

Transformation of meiotic drive into hybrid sterility in Drosophila.

Hybrid male sterility is one of the fastest evolving intrinsic reproductive barriers between recently isolated populations. A leading explanation for the evolution of hybrid male sterility involves genomic conflicts with meiotic drivers in the male germline. There are, however, few examples directly linking meiotic drive to hybrid sterility. In this study, we report that the Sex-Ratio chromosome of Drosophila pseudoobscura, which causes X-chromosome drive within the USA subspecies, causes near-complete male sterility when it is moved into the genetic background of the Bogota subspecies. In addition, we show that this new form of sterility is genetically distinct from the sterility of F1 hybrid males in crosses between USA males and Bogota females. Our observations provide a tractable study system where noncryptic drive within species is transformed into strong hybrid sterility between very young subspecies.

Demographic drivers of reproductive failure in a threatened bird: Insights from a decade of data.

Hatching failure affects up to 77% of eggs laid by threatened bird species, yet the true prevalence and drivers of egg fertilization failure versus embryo mortality as underlying mechanisms of hatching failure are unknown. Here, using ten years of data comprising 4,371 eggs laid by a population of a threatened bird, the hihi (Notiomystis cincta), we investigate the relative importance of infertility and embryo death as drivers of hatching failure and explore population-level factors associated with them. We show that of the 1,438 eggs that failed to hatch (33% of laid eggs) between 2010 and 2020, 83% failed due to embryo mortality, with the majority failing in the early stages of embryonic development. In the most comprehensive estimates of infertility rates in a wild bird population to date, we find that fertilization failure accounts for around 17% of hatching failure overall and is more prevalent in years where the population is smaller and more male biased. Male embryos are more likely to die during early development than females, but we find no overall effect of sex on the successful development of embryos. Offspring fathered by within-pair males have significantly higher inbreeding levels than extra-pair offspring; however, we find no effect of inbreeding nor extra-pair paternity on embryo mortality. Accurately distinguishing between infertility and embryo mortality in this study provides unique insight into the underlying causes of reproductive failure over a long-term scale and reveals the complex risks of small population sizes to the reproduction of threatened species.

Prenatal mercury exposure and the secondary sex ratio: The Japan Environment and Children's Study.

Prior research into the association between prenatal mercury (Hg) exposure and the secondary sex ratio has yielded inconclusive and conflicting results. Notably, no study has used cord blood Hg measurement in this context. Also, the differences in Hg species and the potential modifying role of selenium (Se) on this association remain unexplored. Using data from the Japan Environment and Children's Study, we analyzed mother-child pairs with available data for concentrations of total mercury (THg) and Se in maternal blood during late pregnancy, and THg, inorganic mercury (IHg), methylmercury (MeHg), and Se in cord blood. Logistic regression models were employed to examine the association between Hg and Se biomarkers and the secondary sex ratio. Out of the total sample of 3698 children, 1877 (50.8 %) were male, corresponding to an overall secondary sex ratio of 1.03. After adjusting for maternal age and parity, no significant associations were observed between THg concentrations of maternal blood and the secondary sex ratio. Nevertheless, we identified that two-fold increases in THg, IHg, and MeHg concentrations in cord blood were positively associated with increased odds of having a male child, yielding adjusted odds ratios of 1.13 (95 %CI: 1.04, 1.22), 1.12 (1.03, 1.21), and 1.12 (1.03, 1.22), respectively. When stratified by the median Se concentrations, no apparent differences were detected in the associations between Hg concentrations and the secondary sex ratio. In summary, elevated Hg concentrations in cord blood, but not maternal blood, were associated with an increased probability of male births.

Non-Mendelian transmission of X chromosomes: mechanisms and impact on sex ratios and population dynamics in different breeding systems.

The non-Mendelian transmission of sex chromosomes during gametogenesis carries significant implications, influencing sex ratios and shaping evolutionary dynamics. Here we focus on known mechanisms that drive non-Mendelian inheritance of X chromosomes during spermatogenesis and their impact on population dynamics in species with different breeding systems. In Drosophila and mice, X-linked drivers targeting Y-bearing sperm for elimination or limiting their fitness, tend to confer unfavourable effects, prompting the evolution of suppressors to mitigate their impact. This leads to a complex ongoing evolutionary arms race to maintain an equal balance of males and females. However, in certain insects and nematodes with XX/X0 sex determination, the preferential production of X-bearing sperm through atypical meiosis yields wild-type populations with highly skewed sex ratios, suggesting non-Mendelian transmission of the X may offer selective advantages in these species. Indeed, models suggest X-meiotic drivers could bolster population size and persistence under certain conditions, challenging the conventional view of their detrimental effects. Furthering our understanding of the diverse mechanisms and evolutionary consequences of non-Mendelian transmission of X chromosomes will provide insights into genetic inheritance, sex determination, and population dynamics, with implications for fundamental research and practical applications.

Errors in estimating reproductive parameters with macroscopic methods: a case study on the protogynous blacktip grouper Epinephelus fasciatus (Forsskål 1775).

A size-based, histological analysis of the reproductive life history of the blacktip grouper, Epinephelus fasciatus (Forsskål 1775), was conducted in Indonesia to evaluate the error rate associated with macroscopic reproductive analysis. Histological results indicated that E. fasciatus was protogynous with female L50 at 13.4 cm total length (LT) and a size at sexual transition of 22.0 cm LT. The weight-length relationship for the species was W = 0.011 L3.13. Overall sex ratios were significantly female biased, operational sex ratios were significantly male biased, and sex ratios of mature individuals varied predictably with length from female to male dominance as size increased. No significant relationship between length and batch fecundity was found. The population has a spawning period from February to August. Overall, 54.4% of macroscopic evaluations were incorrect compared to histological results. Of the errors, 14.8% were a failure to detect ovotestes, 12.7% were classifying non-gonadal tissue as ovary or testis, 12.2% were misclassifying sex, and 12.7% were misclassifying maturity status. However, the largest source of error (47.7%) was from misclassifying both sex and maturity status. Of these, 92.9% were macroscopically classified as immature females, but were histologically confirmed to be mature males. Compared to histological results, the only accurate macroscopic results were the absence of a sex-based difference in weight-length relationship and spawning seasonality estimated by a gonadosomatic index (February-June). The use of macroscopic methods to estimate reproductive life-history parameters for sex-changing reefes fish may introduce significant inaccuracies and misinterpretations. Of the parameters estimated by histological methods, size at maturity, size-specific sex ratios, and spawning seasonality have the greatest potential to inform local fishery management policy.

Sex ratio at birth across 100 years in Sweden and risk of cardiovascular disease and all-cause mortality - a national register study.

The human sex ratio at birth (SRB) undergoes temporary changes around a mean proportion of 0.51 male births. SRB has been well studied for historical, geographical, and secular trends, but until now not linked to health outcomes in the total population, e.g. for cardiovascular disease (CVD) or mortality during follow-up of birth cohorts. We used linkage analysis based on national registers in Sweden that cover all births from 1900 to 2016. SRB at birth was calculated by every 10-year birth cohort in all survivors living in 1997 for a follow-up analysis of risk of CVD and mortality with data from national registers. When the highest quartile of SRB was used as reference, a slightly increased risk of fatal CVD (HR 1.03 (95% confidence intervals, CI): 1.02-1.04), non-fatal CVD (HR 1.01; 95%CI: 1.01-1.02) and mortality (HR 1.02; 95%CI, 1.01-1.03) was found after full adjustments in men belonging to the lowest SRB quartile. A similar pattern was also found for fatal CHD in women. in the lowest SBR quartile compared to the highest, HR 1.03 (95%CI: 1.02-1.05). In conclusion, in birth cohorts with a relatively lower than expected number of males born, long-term adverse health effects were observed with slightly increased cardiovascular risk and total mortality at the population level. This could indicate that men belonging to so-called "culled cohorts" in a developed country during the 20th century are characterized by a slightly increased risk that could reflect negative early life influences and environmental exposures in pregnant women resulting in selective loss of male embryos or fetuses. In a public health perspective SRB could be of some importance to monitor as an aspect of birth statistics linked to relatively minor population health effects.

Were fewer boys born in the United States during the early months of the COVID-19 pandemic? A test of the Trivers-Willard hypothesis.

The Trivers-Willard hypothesis predicts that mammalian parents in poor environmental conditions will favor the offspring sex with more reliable chance of reproductive success, which in humans is females. Three months following the onset of the COVID-19 pandemic in South Africa, England, and Wales, there were significant decreases in the sex ratio at birth (SRB) (male births/total live births). We analyzed this ratio with a seasonal autoregressive moving average model, and a logistic regression, using nationwide natality data for all singleton births in the United States from 2015 to 2021 (n = 25,201,620 total births). We identified no significant change in the sex ratio in either analysis. Rather, we observed marked differences in the sex ratio by maternal characteristics of race/ethnicity, age, and education, with more vulnerable groups having lower sex ratios. These findings suggest the SRB may be an important marker of reproductive vulnerability for disadvantaged groups in the United States.

Successive stamen movement in Saxifraga candelabrum is responsive to weather and pollinator visits.

BACKGROUND: Successive stamen movement is a complex plant behavior involving successive uplift of stamens and pollen release, which plays a role in reducing sexual interference, increasing pollen deposition and promoting pollen export. Although reported from several taxa, studies on whether the movement can be influenced by abiotic and biotic factors are scarce. METHODS: In this study, we here for the first time described a pattern of successive stamen movement in Saxifraga candelabrum (Saxifragaceae). We then compared the rates of stamen movement in S. candelabrum under different weather and varying pollinator visits. Pollen packaging and presentation schedule of S. candelabrum were also investigated. RESULTS: The results showed that the number of stamens bent per day in sunny days was significantly higher than overcast and rain. Flowers that receive more pollinator visits (control treatment) had significantly higher number of stamen movement than those that received fewer (removal treatment) and none (bagging treatment). Throughout the staminate phase of a flower, there was a progressive increase in both pollen quantity of individual stamens and pollen presentation during each day. CONCLUSION: Our research demonstrates that successive stamen movement in S. candelabrum was accelerated by favorable weather and increased pollinator visits, which may promote pollen export. Moreover, incremental pollen packaging is likely an adaptation to seasonal regularity in variations of sex ratio resulting from protandry.

Effect of the COVID-19 pandemic on Vogt-Koyanagi-Harada disease.

To determine the disease prevalence rate and clinical characteristics of Vogt-Koyanagi-Harada (VKH) disease among new patients before and after the declaration of a state of emergency (April 7, 2020) in Japan. New patients and patients with newly diagnosed VKH disease were categorized into "Before" and "After" groups based on the initial visit. The prevalence rate, sex ratio, and age of patients newly diagnosed with VKH were compared between the groups. Best-corrected visual acuity (BCVA) and recurrence rates were compared among 59 patients observed for > 12 months after receiving pulse steroid therapy. For reference, we also examined the prevalence rate of patients newly diagnosed with acute angle closure (AAC) in the Before and After groups. The prevalence rates of VKH disease among newly diagnosed patients (P < 0.05) or patients with AAC (P < 0.001) were significantly higher in the After group. No significant differences in sex ratio or age of VKH disease were observed in both groups. BCVA and recurrence rates showed no significant differences. The COVID-19 pandemic increased the prevalence of VKH disease among new patients compared with that of AAC. However, the clinical features of VKH disease were unlikely affected by the COVID-19 pandemic.

The biology of Marchantia polymorpha subsp. ruderalis Bischl. & Boissel. Dub in nature.

Introduction: Though used as the model liverwort in culture for several decades, the biology of Marchantia polymorpha subsp. ruderalis in nature has never been documented in detail in a single account. Methods: Here we synthesize routine field observations documented with hundreds of images of M. ruderalis colonies (or groups) showing sex differentiation over 3 years on two populations of M. ruderalis after major heathland fires in 2020. Results: Initial post-fire establishment is from airborne spores rather than a spore bank but thereafter spread is via gemmae which have less exacting germination requirements. Young sporelings are highly gemmiferous but gemmae production becomes less frequent after sex organ formation. Over the course of a year there are up to three waves of carpocephalum production with the overwhelming majority of antheridiophores appearing 2-3 months ahead of the archegoniophores though no differences in growth rates were apparent between male and female thalli. Spermatozoids are produced almost continuously throughout the year, whilst sporophyte maturation is restricted to the summer months. Discussion: Because of the asynchrony between antheridiophore and archegoniophore production a 1:1 sex ratio is only apparent over this period. The spring months see an excess of males with more females in the summer. An almost 100% fertilization rate, with fertilization distances of up to 19 m far exceeding those in all other bryophytes, is attributed to vast spermatozoid production for most of the year, dispersal on surface oil films between thalli and highly effective intra-thallus spermatozoid transport via the pegged-rhizoid water-conducting system. Archegoniophores do develop on female-only populations but have shorter stalks than those where fertilization has occurred. Eventual disappearance post fires is attributed to a fall in topsoil nutrient levels preventing new sporeling establishment and competition from Ceratodon purpureus and Polytrichum spp. A major drought in the summer of 2022 almost wiped out the heathland Marchantia populations but all the other bryophytes survived.

Wolbachia affect female mate preference and offspring fitness in a parasitoid wasp.

BACKGROUND: Wolbachia are widespread intracellular bacteria in insects that often have high rates of spread due to their impact on insect reproduction. These bacteria may also affect the mating behavior of their host with impacts on the fitness of host progeny. In this study, we investigated the impact of Wolbachia on a preference for mating with young or old males in the parasitoid wasp Habrobracon hebetor. RESULTS: Our results showed that uninfected females from a tetracycline-treated line preferred to mate with young males, whereas Wolbachia-infected females had no preference. Time to mating was relatively shorter in the infected lines. Regardless of Wolbachia infection status, progeny resulting from matings with young males showed higher fitness than those from crosses with old males, and infected females crossed with infected young males showed the highest performance. CONCLUSION: These results suggest an impact of Wolbachia on female mate preference and offspring fitness although it is unclear how this phenomenon increases Wolbachia transmission of infected wasps. © 2024 Society of Chemical Industry.

The Impact of Lifestyle on the Secondary Sex Ratio: A Review.

The secondary sex ratio (SSR), indicating the ratio of male to female live births, has garnered considerable attention within the realms of reproductive biology and public health. Numerous factors have been posited as potential trendsetters of the SSR. Given the extensive research on the impact of daily behaviors and habits on individuals' reproductive health, there is a plausible suggestion that lifestyle choices may also influence the SSR. By synthesizing the existing literature on the current research field, this comprehensive review indicates that an elevated SSR has been associated with an increased intake of fatty acids and monosaccharides, proper nutrition, higher educational levels, financial prosperity, and favorable housing conditions. On the other hand, a decreased SSR may be linked to undernutrition, socioeconomic disparities, and psychological distress, aligning with the Trivers-Willard hypothesis. Occupational factors, smoking habits, and cultural beliefs could also contribute to trends in the SSR. Our review underscores the significance of considering the aforementioned factors in studies examining the SSR and emphasizes the necessity for further research to unravel the mechanisms underpinning these connections. A more profound comprehension of SSR alterations due to lifestyle holds the potential to adequately develop public health interventions and healthcare strategies to enhance reproductive health and overall well-being.

Ambient temperature-related sex ratio at birth in historical urban populations: the example of the city of Poznan, 1848-1900.

This study examines whether exposure to ambient temperature in nineteenth-century urban space affected the ratio of boys to girls at birth. Furthermore, we investigate the details of temperature effects timing upon sex ratio at birth. The research included 66,009 individual births, aggregated in subsequent months of births for the years 1847-1900, i.e. 33,922 boys and 32,087 girls. The statistical modelling of the probability of a girl being born is based on logistic GAM with penalized splines and automatically selected complexity. Our research emphasizes the significant effect of temperature in the year of conception: the higher the temperature was, the smaller probability of a girl being born was observed. There were also several significant temperature lags before conception and during pregnancy. Our findings indicate that in the past, ambient temperature, similar to psychological stress, hunger, malnutrition, and social and economic factors, influenced the viability of a foetus. Research on the effects of climate on the sex ratio in historical populations may allow for a better understanding of the relationship between environmental factors and reproduction, especially concerning historical populations since due to some cultural limitations, they were more prone to stronger environmental stressors than currently.

Sex Ratio at Birth after Concurrent Events of Earthquakes and the COVID-19 Pandemic in Croatia.

The sex ratio at birth (ratio of males to females) has been known to be affected by exogenous shocks such as wars, pollution, natural catastrophes, economic crises, and others. Among these stressful events, both earthquakes and the COVID-19 pandemic have been reported to lower the sex ratio at birth. In this article, a rather unusual situation of two episodes of simultaneous events of COVID-19 lockdown and earthquakes approximately nine months apart (March and December of 2020) is investigated to assess whether they were associated with a bias in sex ratio at birth 3-5 months later (in utero loss) and 9 months later (loss at conception) in Croatia. The monthly time series of sex ratio at birth, total number of births, and total number of both male and female births from January 2010 to December 2021 were analyzed. Seasonally adjusted autoregressive moving-average models were used to estimate the functional form of the time series from January 2010 to February 2020. These results were used to predict the future values of the series until December 2021 and to compare them with the actual values. For all series used, there was no indication of deviation from the values predicted by the models, neither for 3-5 months nor for 9 months after the COVID-19 lockdown and earthquake events. The possible mechanisms of the absence of bias, such as the threshold of the stressful events and its localized reach, as well as the statistical methods employed, are discussed.

Maternal hepatitis B status and Sex at birth: A cross-sectional study in a Ghanaian population.

Maternal carrier status of hepatitis B has been associated with excess sons while maternal immunity to it has been associated with excess daughters at birth. However, the proportion of males at birth (sex ratio) is relatively low in Sub-Saharan Africa despite the relatively high prevalence of hepatitis B. However, no known study has tested this hypothesis in the Ghanaian population; hence the aim of the study. The study was cross-sectional between January and September 2023 at the Tamale Central Maternal and Child Health unit. The study involved 380 mothers of whom mothers with daughters (MD) were 145 (38.2 %) while the rest were mothers with sons (MS). The mothers were aged between 18 and 43 years and were sampled within one week of delivery to singleton births. Maternal venous blood samples were collected and tested for hepatitis B surface antigen (HBsAg), surface antibody (HBsAb), envelop antigen (HBeAg) envelope antibody (HBeAb) and core antibody (HBcAb) using immunochromatographic technique and total testosterone (TT), using ELISA. There was no significant difference in the serum total testosterone level between MD and MS (0.32 ± 0.13 vs 0.32 ± 0.27, P = 0.991). Moreover, while the mothers were seropositive for HBsAg (10.5 %), HBsAb (35.5 %), HBeAg (0.0 %), HBeAb (5.3 %) and HBcAb (11.8 %), there was no significant association between sex at birth and maternal hepatitis B status for HBsAg (ꭓ2: 0.531, P = 0.472), HBsAb (ꭓ2: 2.655, P = 0.140), HBeAb (ꭓ2: 0.251, P = 0.633) and HBcAb (ꭓ2: 0.101, P = 1.000). Maternal hepatitis B status may not be associated with the offspring sex at birth in the studied population from Ghana.