Equal Sex Ratio Research Articles

The Influence of Temperature on Embryonic Respiration, Growth, and Sex Determination in a Western Australian Population of Green Turtles (Chelonia mydas).

The thermal environment of sea turtle embryos has marked effects on many aspects of their development and energetics and has consequences for posthatching stages. Here we incubated Chelonia mydas embryos from Ningaloo Reef in Western Australia at a range of temperatures (27°, 29°, 30°, 31°, 32°, and 30° ± 5°C) to determine development rates and the pivotal temperature for sex determination. We also measured embryonic growth, oxygen consumption, and carbon dioxide production throughout development at 27° and 31°C. Metabolic rates were higher at 31°C than at 27°C, but total energy expenditure was greater at 27°C, with 2,281 mL of oxygen consumed compared with 1,992 mL at 31°C. Respiration at both temperatures showed a pattern typical of sea turtle embryos, with peak rates occurring at approximately 85% of development and then declining toward hatching. Hatchlings produced at higher incubation temperatures developed faster, were smaller, and had larger residual yolk masses than hatchlings produced at lower temperatures. The pivotal temperature that produced an equal sex ratio was 29.2°C, with mixed sexes produced between 27.9° and 30.4°C. Our results showed that the Ningaloo population of C. mydas has somewhat different thermal sensitivities than other C. mydas populations and justified why is it necessary to collect population-specific data to accurately project the impacts of global warming on focal populations.

The importance of core habitat for a threatened species in changing landscapes

Abstract Habitat loss, fragmentation, and alteration of the landscape matrix are interdependent processes, collectively responsible for most recent species extinctions. Thus, determining the extent to which these landscape processes affect animals is critical for conservation. However, researchers have often assumed that interdependent effects are independently related to animals’ responses, underestimating the importance of one or several landscape processes in driving species declines. We demonstrate how to disentangle the interdependent effects of habitat amount, fragmentation, and edge context on population size by assessing abundance of a rapidly declining grassland songbird species (grasshopper sparrow Ammodramus savannarum) in eastern Kansas (USA). We conducted >7,000 point count surveys at >2,000 sites over two breeding seasons, then modelled the direct, interactive, and indirect effects of landscape factors on abundance within spatial scales (200‐, 400‐, 800‐, and 1,600‐m radii) relevant to our focal species’ dispersal behaviour. Sparrow abundance correlated most strongly with landscape structure within 400‐m radii, increasing nonlinearly with grassland area and decreasing with the proportion of grassland near cropland or woody edges. Sparrows’ negative response to cropland edges was mostly an added, indirect consequence of reduced grassland area, whereas sparrows’ stronger negative response to woody edges was not attributable to variation in grassland area. Fragmentation and edge context mattered most in landscapes comprising c. 50%–80% grassland. Synthesis and applications. In our research, abundance of a threatened grassland songbird was influenced more by core grassland area (a function of total grassland area, fragmentation, and edge context) than total grassland area per se. Moreover, a local extinction threshold of c. 50% grassland indicated that small amounts of habitat were unsuitable for our focal species regardless of habitat configuration or matrix type. Local extinction thresholds in response to habitat area provide clear baseline targets for land managers; above those thresholds, configuration and the matrix can be modified to increase abundance of edge‐sensitive animals. Conflicting evidence in the literature regarding the importance of fragmentation and matrix features could be partially explained by species‐level traits, or methodological issues such as defining landscapes at ecologically arbitrary spatial scales, assessing landscape quality using species richness, and ignoring interactive and indirect effects.

Assessing the effect of size-grading for rearing young-of-the-year white-clawed crayfishAustropotamobius pallipes

Crayfish growth rates can vary considerably among individuals from the same brood, and social dominance hierarchies in crustacean species occur frequently. These hierarchies can reduce growth and survival when rearing communal groups. Size-grading and single-sex culturing are the methods used to combat this. A 160-day experiment took place on 288 young-of-the-year captive-born Austropotamobius pallipes, within a closed-circuit, indoor aquaculture facility. Crayfish were reared in three treatments (a) equal numbers of large males + small females (LMSF); (b) equal numbers of small males + large females (SMLF); (c) individuals of the same size, equal sex ratio; plus two control groups of single-sex, same sized individuals. Female survival in the LMSF was significantly reduced (52.8%, SD = 20.7%), whereas overall survival in all other groups was high (83.1%, SD = 15.1%). Male growth (6.3 mm, SD = 0.6 mm) was greater than female growth (4.9 mm, SD = 0.9 mm) across all groups. Cheliped autotomy was significantly greater (8.8%) in males (26.7%, SD = 8.9%) than females (17.9%, SD = 2.7%). This study suggests that young-of-the-year juvenile male A. pallipes grow faster and are more aggressive than females. Large males will suppress and reduce survival in smaller females whereas small males, when housed with larger females, will still grow faster than the females. We suggest that it is sex and not size that is the main factor that causes dominance hierarchies and growth suppression within juvenile A. pallipes. Maintaining juvenile A. pallipes in single-sex groups is optimal to ensure high survival and growth rates.

Differential post-breeding movements of Cetti’s Warblers Cettia cetti in two reedbeds in south-west France

ABSTRACTDifferential post-breeding movements between sex or age groups lead to spatial segregation and can result in the exploitation of different habitats by individuals from the same population. Our aim is to assess whether the use of reedbeds by non-breeding Cetti’s Warblers Cettia cetti involves many transients arriving and departing throughout autumn, or a brief dispersal into this habitat after which individuals stay for a prolonged period. We sampled two reedbeds in south-west France: one dry, or flooded by rain, composed of small mixed reeds, and another with tall reeds and influenced by tidal flooding. We analysed daily capture–recapture data in autumn for two years in each reedbed. Capture–recapture analysis did not detect transients and showed a weak transit dynamic, with some immigration, mainly in the first half of September, and negligible emigration. Thus, reedbeds are used by dispersing birds, mostly the same individuals, with at both sites a strong majority of young females. We interpret this segregation as a product of intraspecific competition. We also noted a higher proportion of adult birds in the dry reedbed (27.6%, with equal sex ratio; more similar to habitats used throughout the year) than in the flooded one (11.7%, with 83.3% being females; unsuitable for breeding). These findings have important implications for the significance of reedbed habitat to this species. Its sustained use by young females makes Cetti’s Warbler vulnerable to the loss of reedbed, or its degradation due to growth of shrubby vegetation or the lack of suitable management.

Geriatric influenza death (GID) score: a new tool for predicting mortality in older people with influenza in the emergency department

Although influenza may cause death in the geriatric population, the best method for predicting mortality in this population is still unclear. We retrospectively recruited older people (≥65 yr) with influenza visiting the emergency department (ED) of a medical center between January 1, 2010, and December 31, 2015. We performed univariate and multivariate logistic regression to identify independent mortality predictors and then developed a prediction score. Four hundred nine older ED patients with a nearly equal sex ratio were recruited. Five independent mortality predictors were identified: severe coma (Glasgow Coma Scale score ≤8), past histories of cancer and coronary artery disease, elevated C-reactive protein levels (>10 mg/dl), and bandemia (>10% band cells). We divided the patients into three mortality risk and disposition groups: (1) low risk (1.1%; 95% confidence interval [CI], 0.5–3.0%); (2) moderate risk (16.7%; 95% CI, 9.3–28.0%); and (3) high risk (40%; 95% CI, 19.8–64.2%). The area under the receiver operating characteristic curve and the Hosmer-Lemeshow goodness of fit of the GID score were 0.86 and 0.578, respectively. The GID score is an efficient and simple tool for predicting mortality in older ED patients with influenza. Further studies are warranted to validate its use.

Shock index predicted mortality in geriatric patients with influenza in the emergency department

BackgroundThe shock index is a rapid and simple tool used to predict mortality in patients with acute illnesses including sepsis, multiple trauma, and postpartum hemorrhage. However, its ability to predict mortality in geriatric patients with influenza in the emergency department (ED) remains unclear. This study was conducted to clarify this issue. MethodsWe conducted a retrospective case-control study, recruiting geriatric patients (≥ 65 years) with influenza visiting the ED of a medical center between January 01, 2010 and December 31, 2015. Demographic data, vital signs, shock index, past histories, subtypes of influenza, and outcomes were included for the analysis. We investigated the association between shock index ≥1 and 30-day mortality. ResultsIn total, 409 geriatric ED patients with mean age of 79.5 years and nearly equal sex ratio were recruited. The mean shock index ± standard deviation was 0.7 ± 0.22 and shock index ≥1 was accounted for in 7.1% of the total patients. Logistic regression showed that shock index ≥1 predicted mortality (odds ratio: 6.80; 95% confidence interval: 2.39–19.39). The area under the receiver operating characteristic was 0.62 and the result of the Hosmer–Lemeshow goodness-of-fit test was 0.23. The sensitivity, specificity, positive predictive value, and negative predictive value of a shock index ≥1 were 30.0%, 94.1%, 20.0%, and 96.4%. ConclusionsA shock index ≥1 has a high specificity, negative predictive value, and good reliability to predict 30-day mortality in geriatric ED patients with influenza.

The Effects of Dietary Whey Lactose and Lactobacillus Agilis Bacteria on the Growth Performance, Physicochemical Conditions of the Digestive Tract and the Caecal Microbial Ecology of Broiler Chickens

Abstract The principal goal of this study was to assess the responses of broiler chickens raised on floor litter to the 2% dietary level of lactose (LAC) originating from dried whey fed in combination with live culture of Lactobacillus agilis bacteria (90 million cells/kg diet) in terms of the performance and basic postslaughter parameters, the lumen pH in some alimentary tract segments, concentration of volatile fatty acids (VFA ) in the total (T) and undissociated (UD) forms and count of selected microbial populations in the caeca determined by fluorescent in-situ hybridisation (FISH). A parallel aim was to evaluate the outcomes from the combined supplementation in comparison with feeding of LAC and the L. agilis bacteria as separate dietary supplements. Six hundred and forty Ross 308 chickens were placed in 16 floor pens (40 birds per pen having equal sex ratio) and were provided with free access to the feed (a mash maize-wheat-soybean meal-based diet) and water. Dietary treatments provided from day 8 to 42 of age were: LAC-free basal diet (CON), LAC-containing diet (CON + LAC), LAC-free diet with the addition of L. agilis (CON + BAC) and LAC-containing diet with addition of L. agilis (CON + LAC + BAC). The LAC supplementation caused significant decreases in the luminal pH of the crop, ileum and caeca, and the addition of the L. agilis bacteria reduced the pH in the crop and caeca. The overall concentration of total (T) volatile fatty acids was higher in the caeca of broilers receiving the LAC-containing diets. Both the LAC and the BAC supplements, independently from one another, resulted in significantly greater caecal levels of UD acetate, propionate and butyrate. The FISH analysis revealed that counts of Bacteroides sp./Prevotella sp. group were higher after the inclusion of LAC in the feed. All three dietary supplementations significantly reduced the total counts of the family Enterobacteriaceae and decreased the number of naturally occurring C. perfringens bacteria compared with the basal control diet (CON). Neither LAC inclusion nor BAC addition to the diet affected the counts of the Clostridium coccoides/Eubacterium rectale group. The synergistic effects of the simultaneous supplementation of LAC and L. agilis were found on the T butyrate concentration and on C. perfringens and the Enterobacteriaceae counts. No improvements in the body weight gains and post-slaughter traits were observed due to uncombined and combined supplementation with 2% LAC and L. agilis, indicating that the shifts in composition of the caecal microbiota toward a healthier composition by using these additives were not large enough to create the positive growth rate and processing yields responses in broilers maintained in a litter-floor environment.

Clinical and molecular characterization of 112 single-center patients with Neurofibromatosis type 1

BackgroundThe aim of this retrospective study was to define clinical and molecular characteristics of a large sample of neurofibromatosis type 1 (NF1) patients, as well as to evaluate mutational spectrum and genotype-phenotype correlation. NF1 is a relatively common neurogenetic disorder (1:2500–1:3000 individuals). It is caused by mutations of the NF1 gene on chromosome 17ql1.2, with autosomal dominant pattern of inheritance and wide phenotypical variability. Café-au-lait spots (CALs), cutaneous and/or subcutaneous neurofibromas (CNFs/SCNFs), skinfold freckling, skeletal abnormalities, Lisch nodules of the iris and increased risk of learning and intellectual disabilities, as well as tumors of the nervous system and other organs are its main clinical features.MethodsThe preliminary group collected 168 subjects with clinical suspicion of NF1. They were evaluated following the National Institutes of Health (NIH) criteria for NF1, revised by Gutmann et al. 1997, integrated for 67 of them by molecular testing. According to these references, 112 of 168 patients were diagnosed as NF1. The sample was characterized by an equal sex ratio (57 males, 55 females) and age distribution ranging from 10 days to 60 years of age (mean age, 13 years).ResultsA wide spectrum of clinical features has been observed in our patients. Mutational analysis resulted positive in 51 cases (76%). Twenty-four mutations detected in our cohort have not been reported to date.ConclusionsThis study may contribute to a better definition of genotypic and phenotypic features of NF1 patients, with respect to further insights into the clinical characterization of the disease. In addition, an amplification of the spectrum of mutations in the NF1 gene has been documented.

School-based malaria prevalence: informative systematic surveillance measure to assess epidemiological impact of malaria control interventions in the Democratic Republic of the Congo

BackgroundIn southern Democratic Republic of the Congo, malaria transmission is stable with seasonal fluctuations. Different measurements can be used to monitor disease burden and estimate the performance of control programmes. Repeated school-based malaria prevalence surveys (SMPS) were conducted from 2007 to 2014 to generate up-to-date surveillance data and evaluate the impact of an integrated vector control programme.MethodsBiannual SMPS used a stratified, randomized and proportional sampling method. Schools were randomly selected from the entire pool of facilities within each Health Area (HA). Subsequently, school-children from 6 to 12 years of age were randomly selected in a proportional manner. Initial point-of-care malaria diagnosis was made using a rapid detection test. A matching stained blood film was later examined by expert microscopy and used in the final analysis. Data was stratified and analysed based on age, survey time and location.ResultsThe baseline SMPS (pre-control in 2007) prevalence was approximately 77%. From 2009 to 2014, 11,628 school-children were randomly screened. The mean age was 8.7 years with a near equal sex ratio. After exclusion, analysis of 10,493 students showed an overall malaria prevalence ratio of 1.92 in rural compared to urbanized areas. The distribution of Plasmodium falciparum malaria was significantly different between rural and urban HAs and between end of wet season and end of dry season surveys. The combined prevalence of single P. falciparum, Plasmodium malariae and Plasmodium ovale infections were 29.9, 1.8 and 0.3% of those examined, respectively. Only 1.8% were mixed Plasmodium species infections. From all microscopically detected infections (3545 of 10,493 samples examined), P. falciparum represented 88.5%, followed by P. malariae (5.4%) and P. ovale (0.8%). Cases with multiple species represented 5.3% of patent infections. Malaria prevalence was independent of age and gender. Control programme performance contributed to a significant decrease in mean P. falciparum infection density in urban compared to rural locations. Some rural areas remained highly refractory to control measures (insecticide-treated bed nets, periodic indoor residual spraying).ConclusionThe SMPS is a useful longitudinal measurement for estimating population malaria prevalence and demonstrating disease burden and impact of control interventions. SMPS can identify refractory areas of transmission and thus prioritize control strategies accordingly.

Male spiders control offspring sex ratio through greater production of female-determining sperm

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.

Plasticity in life history traits of the native Proterorhinus semilunaris suggests high adaptive capacity in its invasive range

Invasion risk assessments are reliant on ecological data that assist the predictions of whether an introduced species will adapt to novel conditions. Data from the native range of potential invaders can thus assist these assessments. Here, the growth and reproductive characteristics of the Western tubenose goby Proterorhinus semilunaris, a Ponto-Caspian gobiid, were assessed in three natural lakes in their native range, as there are few extant data on these traits. Across the three lakes, the gobies were found in varying abundances. Sex ratios varied, with females significantly outnumbering males in only one lake, with equal sex ratios in the other lakes. The fish always showed a positive allometric growth, but had high variability in their somatic growth rates and relative body conditions between the lakes. Scale ageing revealed all populations comprised of individuals to four years old, with one lake having individuals to 5 years old. Reproductive characteristics, including size at maturity, gonado-somatic index and fecundity, did not differ significantly between the lakes. These data suggest that plasticity in aspects of their life history traits provides P. semilunaris with considerable adaptive capacity following their introduction into novel conditions.

Characteristics and prognosis in adult acute myeloid leukemia patients with MLL gene rearrangements

目的分析MLL基因重排成人急性髓系白血病（AML）的临床、实验室特征及预后情况。方法回顾性分析2010年1月至2016年12月确诊的92例MLL基因重排成人AML患者的临床和实验室资料。结果1 417例成人AML（不包括急性早幼粒细胞白血病，均采用FISH方法进行了MLL基因重排分析）患者中检出92例（6.5%）MLL基因重排患者，男女性别比为1∶1，诊断时中位年龄为35.5（15~64）岁，中位WBC 21.00（0.42~404.76）×109/L。按FAB分型标准，78例（84.8%）患者属于急性单核细胞白血病。32例患者检测了11种MLL常见伙伴基因，其中MLL/AF9阳性9例（28.1%），MLL/AF6阳性5例（15.6%），MLL/ELL阳性5例（15.6%），MLL/AF10阳性2例（6.3%），MLL/SETP6阳性1例（3.1%），余10例（31.3%）患者的伙伴基因未知。83例患者可进行疗效分析，中位随访时间为10.3（0.3~74.0）个月，完全缓解（CR）率为85.5%，中位总生存（OS）和无复发生存（RFS）时间分别为15.4和13.1个月，2年OS和RFS率分别为36.6%和29.5%。31例患者进行了异基因造血干细胞移植（allo-HSCT），移植患者的2年OS和RFS率分别为57.9%和52.7%，未移植患者分别为21.4%和14.9%，差异均有统计学意义（P值均<0.001）。进行伙伴基因检测的患者中，9例MLL/AF9阳性患者中位随访时间为6.0（4.1~20.7）个月，3例（33.3%）进行了allo-HSCT；23例非MLL/AF9阳性患者中位随访时间为7.8（0.3~26.6）个月，14例（60.1%）进行了allo-HSCT。两组患者的1年OS率分别为38.1%和55.5%，差异无统计学意义（P=0.688）。多因素分析显示起病时WBC（RR=1.825，95% CI 1.022~3.259，P=0.042）、是否1个疗程达CR（RR=0.130，95% CI 0.063~0.267，P<0.001）以及是否移植（RR=0.169，95% CI 0.079~0.362，P<0.001）为影响MLL基因重排AML患者OS的独立预后因素。结论MLL基因重排成人AML多见于急性单核细胞白血病，MLL/AF9是最常见的伙伴基因。该类型白血病常规化疗虽然缓解率尚可，但极易复发，allo-HSCT可以改善其预后。

Composite intestinal adenoma-microcarcinoid in the colon and rectum: a case series and historical review

BackgroundComposite intestinal adenoma-microcarcinoid (CIAM) is a rare colorectal lesion that mostly comprises a conventional adenomatous component with a minute proportion of neuroendocrine (NE) component. Although microcarcinoids are well-recognized in the setting of chronic inflammatory disorders of the gastrointestinal tract, large intestinal microcarcinoids associated with intestinal adenoma are exceedingly rare and their clinicopathologic characteristics are yet to be elucidated. This study was performed to clarify their clinicopathologic characteristics and to review the relevant literature.MethodsIn total, 24 cases of CIAM in which tumors were excised endoscopically (n = 22) or surgically (n = 2) were retrieved from the Department of Pathology, Daehang Hospital. We analyzed their clinicopathologic characteristics and performed immunohistochemical staining for NE markers to determine their endocrine nature.ResultsCIAM usually developed in middle-aged and elderly patients, with a mean age of 62.0 years (range, 44–81 years). Thirteen patients were men and 11 were women, indicating a nearly equal sex ratio. Unlike classic carcinoid tumors, CIAMs occurred mostly in the colon (83.3% of cases), particularly in the proximal colon. Histologically, the microcarcinoid component consisted of low-grade NE cells arranged in small nests, glands or cords interspersed with glandular elements or less frequently resembled squamous morules. There was no expansile nodular or organoid growth pattern, which is typical of carcinoid tumors. The microcarcinoids were 1–20 mm in size (mean size, 4.7 mm) and were mostly situated in the basal lamina propria with no submucosal layer involvement; none showed desmoplastic reaction or increased proliferative activity. Follow-up data (mean, 23.1 months) were available for 18 patients; all patients are alive and well.ConclusionsTo the best of our knowledge, ours is the largest series of patients with CIAM in the English-language literature. Microcarcinoids found in CIAMs appear to show favorable clinical outcomes regardless of their size, likely due to the absence of submucosal extension and/or increased proliferative activity. We recommend avoiding additional radical surgeries in patients who have endoscopically undergone complete CIAM excision unless they exhibit ominous histologic features such as submucosal extension or increased proliferative activity.

Effects of model-mimic frequency on insect visitation and plant reproduction in a self-mimicry pollination system.

The proportion of mimics and models is a key parameter in mimetic systems. In monoecious plants with self-mimicry pollination systems, the mimic-model ratio is determined by the floral sex ratio. While an equal sex ratio (1:1) could provide the perfect balance between pollen donors and stigma surfaces able to receive the pollen, an unequal ratio could increase pollination by production of a greater number of rewarding, model flowers. The aim of the present study is to test the differences in visitation frequency and reproductive rates of different mimic and model flower arrays in order to assess the efficacy of the mimetic system in a Begonia cucullata population. The frequencies of visitors to groups of flowers with three distinctive sex ratio arrays (male-biased, female-biased and equal ratio) were compared using a Bayesian approach. The reproductive outcomes were compared in order to detect advantages of particular sex ratios. Low visitation frequency was recorded in all arrays. Pollinators showed similar behaviour regardless of sex ratio; they tended to avoid female, rewardless flowers. Pollination quality was highest in the equal sex ratio array. The current study shows that sex ratio plays a critical role in the pollination of B. cucullata and that the efficacy of the self-mimicry system appears to be doubtful. Visitation frequency may be associated with visual or chemical cues that allow pollinators to recognize models and mimics, regardless of their frequency in the population.

Sympatric occurrence and population dynamics of Scylla spp. in equatorial climate: Effects of rainfall, temperature and lunar phase

Mud crabs (Scylla spp.) are known to exist sympatrically in the wild. However, information on their population dynamics and the influence of climate parameters and lunar phase, especially along the equatorial region, are limited. Four sampling stations representing three seas (the Strait of Malacca, South China Sea and Sulu Sea) along the equator were selected. Mud crabs were collected using baited traps during spring tides from April 2012 to July 2013. All three Scylla species, S. olivacea, S. tranquebarica and S. paramamosain live in sympatry in the three seas. Scylla olivacea is the most prevalent species in the Strait of Malacca and South China Sea, whereas S. paramamosain dominates the Sulu Sea. The total crab abundance was not affected by rainfall or temperature. The abundance of S. tranquebarica in Strait of Malacca was negatively correlated with temperature and positively correlated with rainfall whereas the abundance of S. paramamosain positively correlated with temperature only at South China Sea. Scylla tranquebarica was the largest in terms of body size and it showed interchanging abundance trends with S. paramamosain. The average body size of S. paramamosain did not differ significantly with that of S. tranquebarica and S. olivacea. This decrease is most likely attributed to overfishing. Significant seasonal fluctuations in mean carapace width were detected in S. tranquebarica and S. paramamosain, but not in S. olivacea. The monthly sex ratio of all three species occasionally fluctuates above the equal sex ratio value. Lunar phase did not affect species abundance, but males and females were significantly heavier during full moon. These findings serve as a baseline of seasonal variation in crab population dynamics that are useful in mud crab fisheries and resource management.

Spatial distribution, size composition, and dynamics of catches of the Okhotsk skate Bathyraja violacea in the North Pacific Ocean

The results of the long-term (1963–2015) studies of spatial and vertical distributions, dynamics of abundance and size composition of the Okhotsk skate Bathyraja violacea in the North Pacific Ocean are presented. This species is the most abundant at depths of 100–400 m; in the cold season, it migrates to the larger depths for wintering, while it migrates to shallower depths in the warm season. Specimens of the length 12 to 132 cm with prevalence of skates of 50 to 80 cm long were recorded in catches. The difference between males and females in body weight and length was not considerable. Condition factor of specimens decreases from January to August and begins to increase in September. Males dominate among the skates up to 30 cm long, females dominate in the size groups of 30–60 cm and >70 cm, while an almost equal sex ratio is observed in the size group of 60–70 cm. The dynamics of the catches of the Okhotsk skate vary in different regions: in the western Bering Sea and in the Sea of Okhotsk, the catches consistently increased during the study period, the catches increased to the mid-1980s–early 1990s in the Kuril and Kamchatka waters of the Pacific Ocean, and then a decrease has been observed; in the eastern Bering Sea, the peak of catches occurred in the mid-1970s, and then they decreased subsequently.

Early life co-exposures to a real-world PAH mixture and hypoxia result in later life and next generation consequences in medaka (Oryzias latipes)

Acute effects of individual and complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are well documented in vertebrate species. Hypoxia in fish reduces metabolic rate and reproduction. However, less is known about the later life consequences stemming from early-life exposure to PAHs or hypoxia, particularly their co-exposure. To address this, medaka (Oryzias latipes) embryos were exposed to a complex PAH mixture sediment extract from the Elizabeth River, VA (ERSE) at concentrations of 0.1, 0.5, or 1.0% or to one of three different hypoxia scenarios: continuous, nocturnal, or late stage embryogenesis hypoxia. Co-exposures with 0.1% ERSE and each of the hypoxia scenarios were conducted. Results included decreased survival with ERSE, hatching delays with hypoxia, and higher occurrences of deformities with each. The continuous hypoxia scenario caused the most significant changes in all endpoints. These early-life exposures altered later-life growth, impaired reproductive capacity, and reduced the quality of their offspring. ERSE alone resulted in a female-biased sex ratio while continuous or nocturnal hypoxia produced significantly greater numbers of males; and co-exposure produced an equal sex ratio. Exposure to a PAH mixture and hypoxia during early life stages has meaningful later-life and next generational consequences.

Incubation Temperature Modifies Sex Ratio of Hatchlings in Collared Lizards, Crotaphytus collaris

Abstract Increasing evidence indicates that sex-determination mechanisms in reptiles (genotypic sex determination [GSD] and temperature-dependent sex determination [TSD]) are considerably labile and not mutually exclusive. Environmental factors can override GSD in some reptile species and some species shift from GSD to TSD at certain temperatures. We present data on the effects of incubation temperature on sex ratio in Collared Lizard (Crotaphytus collaris) hatchlings. Eggs were incubated at one of seven constant temperatures. More males were produced at both lower and higher temperatures and more females at intermediate temperatures. Although none of the seven treatments produced only females or only males (nor even differed significantly from an equal sex ratio), incubation at different constant temperatures influenced hatchling sex ratios and produced an overall statistically significant pattern, consistent with TSD pattern II but in an inverse way. Even with a lack of evidence, GSD has been suggested ...

The two-fold cost of sex: experimental evidence from a natural system.

Over four decades ago, John Maynard Smith showed that a mutation causing asexual reproduction should rapidly spread in a dioecious sexual population. His reasoning was that the per‐capita birth rate of an asexual population would exceed that of a sexual population, because asexual females do not invest in sons. Hence, there is a cost of sexual reproduction that Maynard Smith called the “cost of males.” Assuming all else is otherwise equal among sexual and asexual females, the cost is expected to be two‐fold in outcrossing populations with separate sexes and equal sex ratios. Maynard Smith's model led to one of the most interesting questions in evolutionary biology: why is there sex? There are, however, no direct estimates of the proposed cost of sex. Here, we measured the increase in frequency of asexual snails in natural, mixed population of sexual and asexual snails in large outdoor mesocosms. We then extended Maynard Smith's model to predict the change in frequency of asexuals for any cost of sex and for any initial frequency of asexuals. Consistent with the “all‐else equal” assumption, we found that the increase in frequency of asexual snails closely matched that predicted under a two‐fold cost.

Fitness Costs of Sexual Harassment-The Price of Persuasion

Females are often subjected to unwanted mating advances from males. Such advances can be costly to both parties. The short-term costs of harassment to females have been widely explored in the literature; however, few studies have measured the direct fitness costs. Moreover, male costs are seldom considered. Conventional wisdom would lead us to hypothesise that sexual harassment is costly; thus, when males and females are housed together, harassment should reduce foraging, growth and reproductive output and may disrupt social interactions. This study quantified harassment costs in both sexes by observing behavioural responses and long-term effects of unsolicited mating in a controlled setting. Sexually mature guppies were subjected to two housing treatments: equal sex ratios or single-sex groups. The effects of male harassment on males and females were assessed by measuring behaviour, growth rate and the number of offspring produced over a period of 6 mo. Contrary to our expectations, our results indicated no significant differences in foraging and growth rates between mixed- and single-sex shoals for either sex. Moreover, there was no significant difference in fry production between mixed- and all-female shoals. Large males showed higher mortality when housed with females. Both sexes showed a reduction in shoaling when in mixed-sex groups. Thus, there appear to be few direct costs of harassment for females in natural, mixed-sex shoals, but males appear to bear significant harassment costs. The study provides insights into reproductive behaviour and life-history traits.