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The study characterized the structure of juveniles and sub-adults of Farfantepenaeus brasiliensis and F. paulensis in the Cananéia-Iguape estuarine lagoon system and its adjacent coastal area by evaluating the period of juvenile recruitment, sex ratio, growth, longevity, natural mortality, and development time until the late juvenile phase. Samples were collected from July 2012 to June 2014. Shrimps were identified by species and sex, and measured (carapace length – CL mm); 889 individuals of F. brasiliensis and 848 of F. paulensis were analysed. Females were more abundant than males for both species. The growth parameters of F. brasiliensis were: CL∞ = 45.5 mm, k = 1.8 year−1 for males and CL∞ = 55.2 mm, k = 1.6 year−1 for females; longevity of 2.52 years (males) and 2.88 years (females); and natural mortality of 1.71 (males) and 1.55 (females). For F. paulensis, the following values were observed: CL∞ = 40.7 mm, k = 2.3 year−1 for males and CL∞ = 56.5 mm, k = 1.9 year−1 for females; longevity of 2.04 years (males) and 2.37 years (females); and natural mortality of 2.39 (males) and 2.05 (females). The juvenile recruitment of both species peaked in January 2014. The development time until late juvenile phase was ~7 months (F. brasiliensis) and ~5 months (F. paulensis). Even though the highest abundance of juveniles did not occur in the closed season, fishing is forbidden in the estuarine area and the migration towards the adult population occurred close to or even during the closed season.
The meadow spittlebug, Philaenus spumarius (L.) (Hemiptera: Aphrophoridae), is the main vector in Europe of the recently detected plant pathogen bacterium Xylella fastidiosa Wells et al. (Xanthomonadales: Xanthomonadaceae). While the ecology of continental populations is well documented, nothing is known about the insular populations of P. spumarius, such as in Corsica, where the bacterium was detected in 2015. Hence, in an epidemiological context, the ecology of P. spumarius has been studied in a maquis landscape in the Ajaccio region between 2017 and 2019. Adults and nymphs were almost exclusively collected on Cistus monspeliensis L. (Cistaceae). However, very few specimens were collected in summer, suggesting a movement of the adults to sheltered habitats. Unfortunately, despite several trapping methods used, the location of adult summer habitat remains unknown for the studied population. It might be tempting to destroy the central plant host of P. spumarius populations. However, as spittlebug nymphs are highly polyphagous on low-growing plant species and as the females can lay eggs in any dead plant tissues, such practice could have limited the impact. Instead, the strong relationship between P. spumarius and C. monspeliensis could be used to monitor spittlebug populations, to limit/concentrate the means of insect control, or in an agronomic context to lure insects away from crops. Maintaining natural arboreal vegetation around agronomic systems could help decrease insect abundance – and potentially, pathogen load – on cultivated species. Such hypotheses need to be further studied by landscape experiments.
Parasitoids can be used as biological agents of pest control. Anagyrus saccharicola Timberlake (Hymenoptera: Encyrtidae) is a parasitoid of the pink sugarcane mealybug Saccharicoccus sacchari (Cockerell) (Hemiptera: Pseudococcidae). Although this mealybug is present in all sugarcane-producing countries, there is limited information regarding this pest and its parasitoid. Aiming to elucidate information on bioecological parameters of A. saccharicola, were evaluated the survival of parasitoid females and males at three temperatures, the host preference of the parasitoid, and the fecundity and longevity of the host. In addition, the parasitism rate of A. saccharicola was estimated based on three factors, feeding, mating, and time. Survival was evaluated at 20, 25, and 30°C. Host preference was conducted on 15-, 20-, and 30-day-old mealybugs. And the parasitism rate was evaluated in fed and unfed, mated and unmated parasitoids and with 24 h and newly emerged. The temperature of 20°C was the most favorable for parasitoid survival. Parasitism occurred at all evaluated ages of the mealybug; however, the preference was for those that were 30-days-old. The parasitized mealybugs longevity was approximately 8 additional days after parasitization, and non-parasitized mealybugs lived for an additional 20 days for mealybugs aged 30 and 20 days at the outset of the tests, and a further 13 days for the 15 days. Feeding and mating after 24 h of emergence resulted in a higher parasitism rate. These findings can contribute to more efficient rearing of A. saccharicola and in the planning of the biological control of S. sacchari in the integrated pest management programs.
The Belgian medical world has acknowledged the diagnosis of transsexualism and accepted Sex Reassignment Surgery (SRS) as one of the steps in the treatment of choice since 1985. This prevalence and demographic study analyses data on all Belgian individuals who have undergone SRS since that year.
All (188) plastic surgeons as well as all gender teams (Antwerp, Bruges, Ghent, and Liège) in Belgium were sent demographic questionnaires to be completed for each of their transsexual patients.
The results show an overall prevalence of 1:12,900 for male-to-female and 1:33,800 for female-to-male transsexuals in Belgium. In Wallonia (the French-speaking region of Belgium) the prevalence is significantly lower than in Flanders (the Dutch-speaking region) and in Brussels (the bilingual capital region). In the total Belgian population the male/female sex ratio is 2.43:1, again with a substantial difference between Wallonia on the one hand and Flanders on the other.
Discussion and Conclusion
While in Flanders and in Brussels the prevalence is comparable to that in other Western European countries, in Wallonia it is markedly lower. Transsexualism in Wallonia appears to be socially less acceptable: persons suffering from gender dysphoria in that part of Belgium encounter more problems accessing gender clinics and receiving treatment.
The temperature-dependent development of Apanteles hemara (Nixon), a larval endoparasitoid of the devastating amaranth pest Spoladea recurvalis (F.) was studied in the laboratory at six constant temperatures (10, 15, 20, 25, 30 and 35 °C), a photoperiod of 12L:12D and a relative humidity of 60–70%. Developmental time decreased significantly with increasing temperature within the range of 15–30 °C. The parasitoid's pupal mortality, successful parasitism rate, adult emergence rate and longevity, sex ratio and fecundity were affected by temperature. The population of A. hemara failed to develop at 10 and 35 °C. The development threshold (Tmin) and the thermal constant (K) were calculated by the linear model while the lethal temperature (Tmax) was determined by the Lactin-1 model. The estimated values of Tmin, Tmax and K by the two models were 10.3 °C, 35.0 °C and 185.18 DD respectively for the total immature development. The estimated value of the optimum temperature using the Taylor model was 30.8 °C. This is the first study to report on the effect of temperature on the developmental parameters of A. hemara giving an insight into its biology. The implications of these findings for the use of A. hemara in biological control are discussed.
The sex ratio question has been an area of growing interest in population dynamics, especially in developing countries with respect to the issue of missing women, but few studies have examined this in sub-Saharan Africa. Both at birth and in the general population, sex ratios follow an expected demographic pattern in the absence of the interference of historical events affecting either males or females in a population. In Zambia, an unexpected demographic pattern of sex ratios is exhibited in census and survey data. This study used data from censuses and surveys conducted from 1969 to 2014 to examine variations in sex ratios in the Zambian population. It was found that sex ratio imbalances were largely due to data deficiencies due to age misreporting and under-enumeration. A consistent under-enumeration of young adult males in the 20–34 years age group was found. A systematic pattern of high sex ratios, above 100, for ages 40+ was found, represented by synthetic cohorts traceable from the 1969 census, progressing to the 2000 census and phased out in the 2010 census. Extremely high adult male mortality was found in 2010 in the 35–59 years age group, primarily attributable to HIV/AIDS. Understanding the demographic pattern of sex ratios in a population is relevant for policies to improve the quality of data collection systems, and socioeconomic development planning, for the young age group population, which is prone under-enumeration.
A survey of Antarctic toothfish (Dissostichus mawsoni) was conducted in the northern Ross Sea region during the winter of 2016 to document the timing and location of spawning activity, to collect biological information about reproductive status during the spawning season and to look for temporal signals in biological data from D. mawsoni that may indicate a spawning migration of mature toothfish from the continental slope region to the northern Ross Sea region. The 58 day survey showed that spawning of D. mawsoni began on some seamounts by early July. No changes were detected between winter and summer in length, age, sex ratio or condition factor distributions for D. mawsoni in the northern Ross Sea as hypothesized following a spawning migration from the slope to the northern Ross Sea region. These results suggest that the distribution of D. mawsoni in the Ross Sea is mainly accomplished through ontogenetic migration and not annual return spawning migrations.
The Trivers–Willard Hypothesis (TWH) states that parents in good conditions bias the sex ratio towards sons and parents in poor conditions bias the sex ratio towards daughters. This study used data from a large nationwide population dataset (N=1,401,851) from the Czech Republic – a modern contemporary society. The study included air pollution and property prices in the TWH estimation, and had a more detailed focus on stillbirths than previous studies. Using official natality microdata from the Czech Statistical Office for years between 1992 and 2010 and data on levels of air pollution in the country over the same period, the study assessed whether the biological and socioeconomic status of mothers and environmental factors affected the sex of children. The results were largely insignificant and not robust across specifications. The presented epidemiological evidence suggests that stillbirths are randomly distributed in the Czech Republic and that the sex ratio is not affected by the socioeconomic status of mothers or by environmental characteristics.
The Chinese white pine beetle Dendroctonus armandi (Coleoptera: Scolytinae) typically displays bivoltinism at altitudes below 1700 m in the Qinling Mountains, China. The periods of host colonization and larval overwintering are two important phases in the life cycle of bark beetles, as it is during these periods that they have to contend with host plant defences and periods of intense cold, respectively. Although during different seasons, the females and males of Chinese white pine beetles show varying tolerances to host plant terpenoids, the sex ratio and survival physiology condition of the two beetle generations are unknown. We investigated the sex ratio of individuals, and also examined the body mass, energy stores, and detoxication enzymes of males and females in each of the two generations in order to determine the overall population stability of each generation. We identified a female-biased sex ratio among adults in both generations. Furthermore, patterns of body mass, energy stores, and detoxication enzymes were found to differ between the two sexes and two seasons. Compared with the males, the females have a larger body mass and higher amounts of stored lipids, which are assumed to be adaptations designed to overcome host resistance and facilitate subsequent oviposition.
The blue shark Prionace glauca is the most abundant species in the artisanal driftnet fishery off the coastal waters of Ivory Coast. The reproductive parameters were investigated with the aim of providing basic information on the reproductive biology for fisheries management. A total of 424 specimens (256 males and 168 females) ranging from 170–330 cm in total length (TL) were sampled between August 2014 and November 2016. Sample for embryonic sex ratio was obtained from 18 litters of 503 individuals (255 males and 248 females). The embryonic sex ratio was not significantly different from 1:1 (χ2 = 0.10, P > 0.05, N = 503). The size at 50% maturity (L50) was 218.1 cm TL for males and 223.3 cm TL for females. The litter size based on the number of embryos varied from 6 to 62, with an average of 30 embryos. Mating started in July whereas ovulation, fertilization and uterine eggs occurred in late October–November. Smallest embryos of 3–5 cm in stretch total length (STL) appeared in uterus from November to January. The embryo size varied widely among months, and well-pigmented embryos were already present in April–May samples, although most of them occurred in August–September, suggesting a gestation period of around 11 months. The absence of neonates in catches, as well as parturition females, does not support a hypothesis that parturition takes place in the Gulf of Guinea.
Coupled with the social practice of female hypergamy, the male surplus within the never-married population means that today's Chinese marriage market is extremely tight in particular for men from a rural background and the least privileged socio-economic categories. Drawing on quantitative data from a survey conducted in 2014–2015, this article sheds light on the situation of single men who are past prime marriage age in three rural districts of Shaanxi particularly affected by this phenomenon. It compares single men's characteristics to those of their married counterparts and offers insights into the heterogeneity of single men with the aim of challenging some commonly accepted assumptions about bachelorhood in rural China. Results suggest a strong internalization of the various characteristics, centred on being able to offer social mobility to a potential wife, that a man is expected to have to be attractive to women in a context where women have more choice in mate selection. We conclude that mate selection is highly marked by class, social norms, social interactions, health, generation and age, and requires the mobilization of certain amounts of individual, social and economic resources. Unwanted bachelorhood would thus be better understood using an intersectional approach rather than mainly in numeric terms.
The present study investigated the population dynamics of Hepatus pudibundus in the Cananéia region, in southern São Paulo state, Brazil, focusing on population structure, growth parameters, longevity, sex ratio, reproduction and recruitment juvenile period. Sampling was performed monthly at seven stations from July 2012 to June 2014, using a shrimp fishing boat. A total of 1650 specimens were collected: 551 males and 1099 females. The males were larger than females. Reproductive females were captured throughout the study period and juveniles were captured in most months. Both of these demographic categories were positively correlated with temperature. Growth parameters showed differences between sexes: CW∞ = 78.91 mm, k = 0.0066 day−1, t0 = 0.0965 for males and CW∞ = 69.71 mm, k = 0.0053 day−1, t0 = −0.2404 for females. Longevity was estimated at 1.91 and 2.40 years for males and females, respectively. The findings provide a greater understanding of the life cycle in this species. Additionally, since trawl nets are not selective, this study also provides information for better trawl fishery management, addressing not only the target shrimp but also the by-catch species.
Female family headship has strong implications for endemic poverty in the United States. Consequently, it is imperative to explore the chief factors that contribute to this problem. Departing from prior literature that places significant weight on welfare-incentive effects, our study highlights the role of male marriageability in explaining the prevalence of never-married female family headship for blacks and whites. Specifically, we examine racial differences in the effect of male marriageability on never-married female headship from 1980 to 2010. By exploiting data from IPUMS-USA (N = 4,958,722) and exogenous variation from state-level sentencing reforms, the study finds that the decline in the relative supply of marriageable males significantly increases the incidence of never-married female family headship for blacks but not for whites.
Superparasitism is an adaptive strategy in solitary parasitoids, yet insufficient evidence confirms this in gregarious ones. We here ask whether the gregarious parasitoid Oomyzus sokolowskii is able to discriminate in attack and progeny allocation between parasitized and unparasitized Plutella xylostella larvae, and how the parasitoid allocates brood size and sex to superparasitized hosts due to some circumstances. We found that female parasitoids preferred unparasitized to parasitized host larvae, and allocated a smaller brood with more males in the later than in the former host. Brood size and sex ratio decreased from superparasitized hosts with a 48 h interval since a previous attack compared with one without an interval; they also declined from the host superparasitized by the parasitoid with oviposition experience compared with one without it. Brood size and sex ratio did not differ between the host superparasitized by the same parasitoid as in the first attack and that by a different one. Our findings suggest that O. sokolowskii females may adjust their oviposition decisions on progeny allocation in response to parasitized P. xylostella larvae to maximize their fitness gains from superparasitism.
This study evaluated the population structure, growth and longevity of Xiphopenaeus kroyeri in the State of Sergipe. The obtained data were compared with other populations on a latitudinal scale in order to evaluate whether the latitudinal paradigm applies to this species. Shrimp sampling took place monthly from September 2013 to August 2014, in nine stations distributed at 5, 15 and 30 m depths, using a shrimp fishery boat equipped with a ‘double rig’ net. Sexual maturity was estimated by the logistic function y = a/(1 + b*exp(-cx)), and the sex ratio was analysed with the Chi-square test. The individual growth rate was estimated using the von Bertalanffy model, and the longevity was estimated by the inverse form of this formula. A total of 6418 (3457 females and 2961 males) was analysed. The size at onset of sexual maturity was 12 mm of carapace length (CL) for males and 12.5 mm CL for females. The total sex ratio did not differ from the expected (1:1). Males exhibited higher growth coefficients (k) and smaller asymptotic growth (CC∞ = 28.74 mm, k = 0.0081 day−1) than females (CC∞ = 30.79 mm, k = 0.0058 day−1). The estimated longevity (years) was 1.55 for males and 2.15 for females. No evident latitudinal pattern was observed regarding the size at onset of sexual maturity or the growth parameters for X. kroyeri. The information found, besides contributing to the knowledge about the biology of this shrimp, can also clarify hypotheses presented in relation to the latitudinal paradigm along the Brazilian coast.
In laboratory experiments, we investigated how media with varying ratio of peat:sand and two levels of compaction influence dispersal success of entomopathogenic nematode (EPN) species with different foraging strategies: Steinernema carpocapsae (ambusher), Heterorhabditis downesi (cruiser) and Steinernema feltiae (intermediate). Success was measured by the numbers of nematodes moving through a 4 cm column and invading a wax moth larva. We found that both compaction and increasing peat content generally decreased EPN infective juvenile (IJ) success for all three species. Of the three species, H. downesi was the least affected by peat content, and S. carpocapsae was the most adversely influenced by compaction. In addition, sex ratios of the invading IJs of the two Steinernema species were differentially influenced by peat content, and in the case of S. feltiae, sex ratio was also affected by compaction. This indicates that dispersal of male and female IJs is differentially affected by soil parameters and that this differentiation is species-specific. In conclusion, our study shows that organic matter: sand ratio and soil compaction have a marked influence on EPN foraging behaviour with implications for harnessing them as biological pest control agents.
The present study investigated the population dynamics of Exhippolysmata oplophoroides in an area influenced by upwelling, focusing on reproductive period, sex ratio, growth rate, longevity, mortality, relative growth and size of sex change. We also tested the hypothesis that the appendices internae increased in size with sex change from the male to the simultaneous hermaphrodite phase as possible replacements for the male appendices masculinae, which are reduced or lost at sex change. Population structure was assessed by the distribution of size frequency in three demographic groups: male phase, hermaphrodite phase with, and without embryos. For relative growth analysis, the length of the following structures was measured: carapace, second pleuron, first pereopod, second pereopod, appendices internae of the second to fifth pleopods, and appendix masculina. Smaller size classes were composed only by male-phase individuals. The sex ratio was significantly biased towards the simultaneous hermaphrodite phase. Reproduction was continuous in the population throughout the year. Slower growth rates but higher maximum body sizes than those estimated at other locations in south-eastern Brazil were observed in the population studied. Cooler temperatures and higher nutrient levels associated with upwelling may have produced this pattern of reproduction and growth, similar to that found in more southerly austral latitudes. We also found that sex change influences the relative growth of body structures such as the second pereopods, appendices internae, and appendix masculina, and hypotheses on the adaptive value of such allometric growth are proposed.
Polymorphism may allow individuals to expand habitat use through morph-specific resource demands. However, the underlying mechanisms maintaining different morphotypes in nature are difficult to identify. We sampled populations of the shrimp Hippolyte obliquimanus in the macroalgae Sargassum furcatum and Galaxaura marginata to examine morph-specific distribution patterns, population structure and female reproductive output, as an initial step to understand polymorphism in this species. Two main colour morphotypes were identified: homogeneous shrimps (H), which change their colour, mostly from pink to greenish-brown tones, and striped translucent shrimps (ST), whose colour remain unaltered. Distribution of individuals between habitats was clearly morph-specific. H shrimps occupied colour-matching substrates, mainly Sargassum, where they can attain large densities, and ST individuals were evenly distributed in both algae. Brood production and size-fecundity relationships were similar between morphs and habitats, suggesting these are relatively fixed traits in the population. However, sex proportions, defined as the male to female ratio, were different between morphs and macroalgae. H shrimps were chiefly females (1:2.04) and ST shrimps mostly males (1:0.30). Given the likely polygynic pure-search mating system in H. obliquimanus, the female-biased sex ratio observed in Sargassum is apparently more advantageous than the Mendelian proportion found in Galaxaura habitat. Clustering on vegetated habitat, the female-biased H morph may be relatively cryptic and sedentary, compared with the male-biased ST morph which apparently combines a more neutral camouflage strategy to a generalized habitat use. Altogether, results suggest that selection for sex-specific traits favours the maintenance of polymorphism in H. obliquimanus.
Sirex noctilio Fabricius (Hymenoptera, Siricidae) is rare and rarely studied where it is native in Eurasia, but is a widespread pest of pines in the Southern Hemisphere. Here we report on the abundance, basic biology, host use patterns and natural enemies of native S. noctilio in Galicia, Spain. Most trees attacked by S. noctilio failed to produce any adult progeny: >90% of emergences came from <20% of the attacked trees. The highest reproduction was in Pinus pinaster, followed by Pinus sylvestris and Pinus radiata. The proportions of S. noctilio requiring 1, 2 or 3 years for development were 0.72: 0.24: 0.04. Delayed development could be an adaptation to avoid parasitic nematodes, which sterilized 41.5% adults with one year generation time but only 19% of adults with 2 years generation time. Hymenoptera parasitoids accounted for 20% mortality. Sex ratios were male biased at 1: 2.9. Body size and fecundity were highly variable and lower than previously reported from the Southern Hemisphere. On attacked trees, there were 5–20 attacks per standard log (18 dm2), with usually 1–3 drills per attack. Attack densities and drills per attack were higher in trees that subsequently died. The production of S. noctilio per log was positively related to total attacks, and negatively related to: (1) attack density, (2) incidence of blue stain from Ophiostoma fungi and (3) frequency of lesions in plant tissue around points of attack. A preliminary life table for S. noctilio in Galicia estimated effects on potential population growth rate from (in decreasing order of importance) host suitability, unequal sex ratio, parasitic nematodes and Hymenoptera parasitoids.
Sex change, or sequential hermaphroditism, occurs in the plant and animal kingdoms and often determines a predominance of the first sex. Our aim was to explore changes in sex ratios within the range of the species studied: Patella vulgata and Patella depressa. The broad-scale survey of sex with size of limpets covered a range of latitudes from Zambujeira do Mar (southern Portugal) to the English Channel. Indirect evidence was found for the occurrence of protandry in P. vulgata populations from the south of England, with females predominating in larger size-classes; cumulative frequency distributions of males and females were different; sex ratios were biased towards males and smallest sizes of males were smaller than the smallest sizes of females. In contrast in Portugal females were found in most size-classes of P. vulgata. In P. depressa populations from the south coast of England and Portugal females were interspersed across most size-classes; size distributions of males and females and size at first maturity of males and females did not differ. P. depressa did, however, show some indications of the possibility of slight protandry occurring in Portugal. The test of sex ratio variation with latitude indicated that P. vulgata sex ratios might be involved in determining the species range limit, particularly at the equatorward limit since the likelihood of being male decreased from the south coast of England to southern Portugal. Thus at the southern range limit, sperm could be in short supply due to scarcity of males contributing to an Allee effect.