Sexual dimorphism in Amphisbaena nigricauda (Reptilia, Squamata, Amphisbaenidae) from Southeastern Brazil

Amphisbaena nigricauda Gans, 1966 is a small, poorly known amphisbaenid endemic to the restinga of the states of Espírito Santo and Bahia, Brazil. We analyze 178 specimens collected in Vitória municipality, state of Espírito Santo, Brazil, to investigate whether this species show sexual dimorphism in pre-cloacal pores and in morphological characters. Sex was determined by a ventral incision and direct inspection of gonads. A PCA analysis was performed to generate a general body size measurement. A T test and the non-parametric Mann-Whitney test were used to assess whether this species show sexual dimorphism on five morphometric and five meristic characters, respectively. Sex could not be determined in 36 specimens because they were mutilated in the posterior portion of their bodies. The diagnosis of the species is redefined based on this sample size: the smallest number of body annuli changes from 222 to 192, the number of dorsal and ventral segments in an annulus in the middle of the body changes to 9-11/13-16 (instead of 10/16), and the autotomic tail annulus lies between annulus 7-10 (instead of 6-9). The number of tail annuli remained within the known range of variation of the species (19-24). None of the 80 females analyzed showed pre-cloacal pores, whereas within males 59 out of 62 specimens displayed four and two specimens displayed five pre-cloacal pores. A single male did not possess pre-cloacal pores, but showed irregular scales on its cloacal region. Sex-based difference based on presence or absence of pre-cloacal pores as well as males with wider head was seen in other Neotropical amphisbaenids. However, a pattern of body size differences between males and females has not been identified so far in the few amphisbaenid species studied in this regard. Further studies on this taxonomic group are still needed to elucidate the existence of general patterns of sexual dimorphism and to identify the selective pressures driving these patterns.

Contribuição ao estudo dos Embiídeos: IV. Polimorfismo sexual da região cefálica de Embolyntha batesi Mac lachlan, 1877 (Embiidina, Embiidae)

Em continuação as pesquisas que vimos realizando nos Embiídeos é feito um estudo comparado das peças bucais entre machos e fêmeas de Embolyntha batesi. A cabeça é prognata recoberta por diminutas cerdas. É a região mais resistente do inseto, devido proteger, além de outros órgãos, principalmente, o sistema nervoso. Varia de tamanho nos dois sexos com os índices (comprimento : largura) na fêmea de 1,06 e nos machos de 1,36; a cabeça da fêmea é achatada, enquanto que a dos machos é alongada. Quase tôdas as suturas são visíveis nos sexos, com excessão de algumas, como é o caso da coronal e post-frontal dos machos. De tôdas as suturas, a temporal é a mais interessante, limita a região do vertex com as genas, ao mesmo tempo que origina um sulco profundo, que penetra na cápsula craniana fazendo parte do esqueleto interno da cabeça, e sendo responsável pelo aspecto diferente das mesmas. A sutura temporal, na região ventral, separa as genas das subgenas. A sutura hipostomal, em ambos os sexos, é muito acentuada, e na sua parte mais interna, vêm se inserir os ramos posteriores do tentório, e, ainda lateralmente, as maxilas. O tentório é primitivo, tendo um corpo central, de forma quadrangular e, de cada ângulo parte um ramo; dois anteriores, menores, que se dirigem para a região dorsal onde se bifurcam, indo ter próximo á base das antenas e mandíbulas, e dois ramos posteriores que seguem a direção ventral, indo ter á região hipostomal. As antenas são filiformes, variando o número de segmentos. Os olhos dos machos são reniformes, salientes e grandes, enquanto que os das fêmeas são pequenos, ovais e achatados. O número de omatídeos de macho é 34, e, na fêmea é 41, em uma determinada área. O clípeo quase não se diferencia da fronte, porém encontra-se dividido em anti-clípeo e post-clípeo. A sutura do clípeo-labro é bem acentuada, deixando transparecer, após a diafanização do material, um espessamento da cutícula na sua região mais interna, destinada a implantação dos músculos que movimentam o labro. Na parte ventral o labro apresenta sensilas, que variam quanto a forma, tamanho e estrutura nos dois sexos. As mandíbulas apresentam-se muito diferentes devida sua função, isto é, trituradora nas fêmeas e preensora nos machos. Pela simples morfologia das mandíbulas podemos identificar o sexo nos Embiídeos. Em ambos temos dentes incisivos e molares, porém mais acentuados nas fêmeas. Nos machos a região interna da mandíbula tem a forma côncava, com cutícula...

Inbreeding avoidance through kin recognition: choosy females boost male dispersal.

Inbreeding avoidance is predicted to induce sex biases in dispersal. But which sex should disperse? In polygynous species, females pay higher costs to inbreeding and thus might be expected to disperse more, but empirical evidence consistently reveals male biases. Here, we show that theoretical expectations change drastically if females are allowed to avoid inbreeding via kin recognition. At high inbreeding loads, females should prefer immigrants over residents, thereby boosting male dispersal. At lower inbreeding loads, by contrast, inclusive fitness benefits should induce females to prefer relatives, thereby promoting male philopatry. This result points to disruptive effects of sexual selection. The inbreeding load that females are ready to accept is surprisingly high. In absence of search costs, females should prefer related partners as long as delta<r/(1+r) where r is relatedness and delta is the fecundity loss relative to an outbred mating. This amounts to fitness losses up to one-fifth for a half-sib mating and one-third for a full-sib mating, which lie in the upper range of inbreeding depression values currently reported in natural populations. The observation of active inbreeding avoidance in a polygynous species thus suggests that inbreeding depression exceeds this threshold in the species under scrutiny or that inbred matings at least partly forfeit other mating opportunities for males. Our model also shows that female choosiness should decline rapidly with search costs, stemming from, for example, reproductive delays. Species under strong time constraints on reproduction should thus be tolerant of inbreeding.

Sexual dimorphism in resource acquisition and deployment: both size and timing matter.

Background and Aims The males and females of many dioecious plant species differ from one another in important life-history traits, such as their size. If male and female reproductive functions draw on different resources, for example, one should expect males and females to display different allocation strategies as they grow. Importantly, these strategies may differ not only between the two sexes, but also between plants of different age and therefore size. Results are presented from an experiment that asks whether males and females of Mercurialis annua, an annual plant with indeterminate growth, differ over time in their allocation of two potentially limiting resources (carbon and nitrogen) to vegetative (below-and above-ground) and reproductive tissues.Methods Comparisons were made of the temporal patterns of biomass allocation to shoots, roots and reproduction and the nitrogen content in the leaves between the sexes of M. annua by harvesting plants of each sex after growth over different periods of time.Key Results and Conclusions Males and females differed in their temporal patterns of allocation. Males allocated more to reproduction than females at early stages, but this trend was reversed at later stages. Importantly, males allocated proportionally more of their biomass towards roots at later stages, but the roots of females were larger in absolute terms. The study points to the important role played by both the timing of resource deployment and the relative versus absolute sizes of the sinks and sources in sexual dimorphism of an annual plant.

Genetical exchanges between one Biomphalaria glabrata (Gastropoda: Planorbidae) and a varying number of partners

When one pigmented Biomphalaria glabrata is mated with 1 to 20 albino snails, the percentage of albino parent producing pigmented offspring decreases while the percentage of parent laying albino offspring increases. If the number of snaisl/group increases, the mean duration of the use of allosperm decreases.

On the fate of sexual traits under asexuality.

Environmental shifts and life-history changes may result in formerly adaptive traits becoming non-functional or maladaptive. In the absence of pleiotropy and other constraints, such traits may decay as a consequence of neutral mutation accumulation or selective processes, highlighting the importance of natural selection for adaptations. A suite of traits are expected to lose their adaptive function in asexual organisms derived from sexual ancestors, and the many independent transitions to asexuality allow for comparative studies of parallel trait maintenance versus decay. In addition, because certain traits, notably male-specific traits, are usually not exposed to selection under asexuality, their decay would have to occur as a consequence of drift. Selective processes could drive the decay of traits associated with costs, which may be the case for the majority of sexual traits expressed in females. We review the fate of male and female sexual traits in 93 animal lineages characterized by asexual reproduction, covering a broad taxon range including molluscs, arachnids, diplopods, crustaceans and eleven different hexapod orders. Many asexual lineages are still able occasionally to produce males. These asexually produced males are often largely or even fully functional, revealing that major developmental pathways can remain quiescent and functional over extended time periods. By contrast, for asexual females, there is a parallel and rapid decay of sexual traits, especially of traits related to mate attraction and location, as expected given the considerable costs often associated with the expression of these traits. The level of decay of female sexual traits, in addition to asexual females being unable to fertilize their eggs, would severely impede reversals to sexual reproduction, even in recently derived asexual lineages. More generally, the parallel maintenance versus decay of different trait types across diverse asexual lineages suggests that neutral traits display little or no decay even after extended periods under relaxed selection, while extensive decay for selected traits occurs extremely quickly. These patterns also highlight that adaptations can fix rapidly in natural populations of asexual organisms, in spite of their mode of reproduction.

Sexual dysfunction among young men : prevalence and associated factors

Les dysfonctions sexuelles représentent une préoccupation importante et parfois mésestimée dans la population masculine générale. L'éjaculation précoce et les dysfonctions érectiles faisant partie des dysfonctions sexuelles les plus fréquentes, nous avons choisi, dans le présent article, de nous concentrer sur ces deux aspects. Selon plusieurs études, la prévalence d'éjaculation précoce se situe entre 17 et 30%. Les associations décrites avec l'éjaculation précoce concernent le stress, la dépression et un jeune âge (<25 ans). La prévalence de dysfonction érectile, quant à elle, oscille entre 2 et plus de 80% dépendant principalement de l'âge. Beaucoup d'autres facteurs associés ont été décrits dans la littérature, tels que le diabète, les pathologies cardiovasculaires ou neurologiques, les médicaments, l'obésité ou l'inactivité physique. Tous ces facteurs étant plus fréquents au sein de populations vieillissantes, nous disposons de peu d'études concernant la dysfonction érectile chez de jeunes hommes. Notre étude propose donc d'évaluer la prévalence d'éjaculation précoce et de dysfonction érectile chez une population de jeunes hommes et d'étudier les associations possibles avec les consommations de substances, l'index de masse corporelle (IMC), l'activité physique ou la santé mentale. Chaque homme suisse entre 18 et 25 ans est appelé à participer à 2 journées de recrutement militaire. De septembre 2010 à mai 2011, les jeunes hommes recrutés à Lausanne et à Zürich (N= 9761) ont été invités à participer à l'étude C-SURF (Cohort Study on Substance Use Risk Factors). 5276 d'entre eux acceptèrent de répondre au questionnaire complet, et 73% (N=3886) le firent de manière effective. Le but de notre recherche étant d'étudier les dysfonctions sexuelles, nous nous sommes concentrés sur les participants sexuellement actifs (N=2507) et les avons divisés en 2 groupes, selon qu'ils présentaient ou non la dysfonction étudiée. Pour chaque dysfonction (éjaculation précoce et dysfonction érectile), nous avons utilisé une analyse bivariée afin de comparer les deux groupes (avec ou sans trouble) quant à d'éventuels facteurs associés. A cause de la nature transversale de l'étude, nous ne pouvions pas postuler de lien de cause à effet entre ces facteurs et les dysfonctions sexuelles, raison pour laquelle nous avons choisi d'utiliser des modèles log-linéaires pour mettre en exergue les associations significatives. Nos résultats montrent une prévalence d'éjaculation précoce de 11.4% avec comme associations principales la consommation de tabac et de drogues illégales (autres que le cannabis). La prévalence des dysfonctions érectiles est quant à elle proche du 30% et s'associe principalement avec l'usage de médicaments, ainsi qu'avec la santé physique et la santé mentale. Un jeune homme suisse sur trois souffre ainsi d'au moins une dysfonction sexuelle. Beaucoup de facteurs compromettants pour la santé y sont possiblement associés, raison pour laquelle les professionnels de la santé devraient saisir chaque occasion pour parler de sexualité avec leurs jeunes patients de sexe masculin.

Genetics of decayed sexual traits in a parasitoid wasp with endosymbiont-induced asexuality.

Trait decay may occur when selective pressures shift, owing to changes in environment or life style, rendering formerly adaptive traits non-functional or even maladaptive. It remains largely unknown if such decay would stem from multiple mutations with small effects or rather involve few loci with major phenotypic effects. Here, we investigate the decay of female sexual traits, and the genetic causes thereof, in a transition from haplodiploid sexual reproduction to endosymbiont-induced asexual reproduction in the parasitoid wasp Asobara japonica. We take advantage of the fact that asexual females cured of their endosymbionts produce sons instead of daughters, and that these sons can be crossed with sexual females. By combining behavioral experiments with crosses designed to introgress alleles from the asexual into the sexual genome, we found that sexual attractiveness, mating, egg fertilization and plastic adjustment of offspring sex ratio (in response to variation in local mate competition) are decayed in asexual A. japonica females. Furthermore, introgression experiments revealed that the propensity for cured asexual females to produce only sons (because of decayed sexual attractiveness, mating behavior and/or egg fertilization) is likely caused by recessive genetic effects at a single locus. Recessive effects were also found to cause decay of plastic sex-ratio adjustment under variable levels of local mate competition. Our results suggest that few recessive mutations drive decay of female sexual traits, at least in asexual species deriving from haplodiploid sexual ancestors.

Factors Affecting Audit Quality in the 2007 UK Regulatory Environment: Perceptions of Chief Financial Officers, Audit Committee Chairs and Audit Engagement Partners

In line with global changes, the UK regulatory regime for audit and corporate governance has changed significantly since the Enron scandal, with an increased role for audit committees and independent inspection of audit firms. UK listed company chief financial officers (CFOs), audit committee chairs (ACCs) and audit partners (APs) were surveyed in 2007 to obtain views on the impact of 36 economic and regulatory factors on audit quality. 498 usable responses were received, representing a response rate of 36%. All groups rated various audit committee interactions with auditors among the factors most enhancing audit quality. Exploratory factor analysis reduces the 36 factors to nine uncorrelated dimensions. In order of extraction, these are: economic risk; audit committee activities; risk of regulatory action; audit firm ethics; economic independence of auditor; audit partner rotation; risk of client loss; audit firm size; and, lastly, International Standards on Auditing (ISAs) and audit inspection. In addition to the activities of the audit committee, risk factors for the auditor (both economic and certain regulatory risks) are believed to most enhance audit quality. However, ISAs and the audit inspection regime, aspects of the ‘standards-surveillance compliance’ regulatory system, are viewed as less effective. Respondents commented that aspects of the changed regime are largely process and compliance driven, with high costs for limited benefits, supporting psychological bias regulation theory that claims there is overconfidence that a useful regulatory intervention exists.

Meta-analysis identifies 13 new loci associated with waist-hip ratio and reveals sexual dimorphism in the genetic basis of fat distribution.

Waist-hip ratio (WHR) is a measure of body fat distribution and a predictor of metabolic consequences independent of overall adiposity. WHR is heritable, but few genetic variants influencing this trait have been identified. We conducted a meta-analysis of 32 genome-wide association studies for WHR adjusted for body mass index (comprising up to 77,167 participants), following up 16 loci in an additional 29 studies (comprising up to 113,636 subjects). We identified 13 new loci in or near RSPO3, VEGFA, TBX15-WARS2, NFE2L3, GRB14, DNM3-PIGC, ITPR2-SSPN, LY86, HOXC13, ADAMTS9, ZNRF3-KREMEN1, NISCH-STAB1 and CPEB4 (P = 1.9 × 10⁻⁹ to P = 1.8 × 10⁻⁴⁰) and the known signal at LYPLAL1. Seven of these loci exhibited marked sexual dimorphism, all with a stronger effect on WHR in women than men (P for sex difference = 1.9 × 10⁻³ to P = 1.2 × 10⁻&supl;³). These findings provide evidence for multiple loci that modulate body fat distribution independent of overall adiposity and reveal strong gene-by-sex interactions.

Sexual distinction between 5th instar nymphs of six species of Triatominae (Hemiptera, Reduviidae)

The aim of this paper is to present the analysis of sexual morphological differences observed in 5th instar nymphs of the following species: Panstrongylus megistus; Rhodnius neglectus; Triatoma brasiliensis; T. infestans; T. matogrosensis and T. tibiamaculata. Male and female nymphs were examined and photographed with a Scanning Electron Microscope. The 9th segment dimensions of dorsal and ventral faces were determined through a Profile Projector. Results and statistical analysis showed significant differences: the 9th sternite is significantly broader in male than female nymphs, while in five species; tergites in female nymphs are broad and in male are narrow.

Inconsistency between different measures of sexual selection.

Measuring the intensity of sexual selection is of fundamental importance to the study of sexual dimorphism, population dynamics, and speciation. Several indices, pools of individuals, and fitness proxies are used in the literature, yet their relative performances are strongly debated. Using 12 independent common lizard populations, we manipulated the adult sex ratio, a potentially important determinant of the intensity of sexual selection at a particular time and place. We investigated differences in the intensity of sexual selection, as estimated using three standard indices of sexual selection-the standardized selection gradient (β'), the opportunity of selection (I), and the Bateman gradient (βss)--calculated for different pools of individuals and different fitness proxies. We show that results based on estimates of I were the opposite of those derived from the other indices, whereas results based on estimates of β' were consistent with predictions derived from knowledge about the species' mating system. In addition, our estimates of the strength and direction of sexual selection depended on both the fitness proxy used and the pool of individuals included in the analysis. These observations demonstrate inconsistencies in distinct measures of sexual selection and underscore the need for caution when comparing studies and species.

The Multiple-partners assignment game with heterogeneous sales and multi-unit demands: competitive equilibria

A multiple-partners assignment game with heterogeneous sales and multiunit demands consists of a set of sellers that own a given number of indivisible units of (potentially many different) goods and a set of buyers who value those units and want to buy at most an exogenously fixed number of units. We define a competitive equilibrium for this generalized assignment game and prove its existence by using only linear programming. In particular, we show how to compute equilibrium price vectors from the solutions of the dual linear program associated to the primal linear program defined to find optimal assignments. Using only linear programming tools, we also show (i) that the set of competitive equilibria (pairs of price vectors and assignments) has a Cartesian product structure: each equilibrium price vector is part of a competitive equilibrium with all optimal assignments, and vice versa; (ii) that the set of (restricted) equilibrium price vectors has a natural lattice structure; and (iii) how this structure is translated into the set of agents' utilities that are attainable at equilibrium.

RNA-driven cyclin-dependent kinase regulation: when CDK9/cyclin T subunits of P-TEFb meet their ribonucleoprotein partners.

The positive transcription elongation factor (P-TEFb) consists of CDK9, a cyclin-dependent kinase and its cyclin T partner. It is required for transcription of most class II genes. Its activity is regulated by non-coding RNAs. The 7SK cellular RNA turns the HEXIM cellular protein into a P-TEFb inhibitor that binds its cyclin T subunit. Thus, P-TEFb activity responds to variations in global cellular transcriptional activity and to physiological conditions linked to cell differentiation, proliferation or cardiac hypertrophy. In contrast, the Tat activation region RNA plays an activating role. This feature at the 5' end of the human immunodeficiency (HIV) viral transcript associates with the viral protein Tat that in turn binds cyclin T1 and recruits active P-TEFb to the HIV promoter. This results in enhanced P-TEFb activity, which is critical for an efficient production of viral transcripts. Although discovered recently, the regulation of P-TEFb becomes a paradigm for non-coding RNAs that regulate transcription factors. It is also a unique example of RNA-driven regulation of a cyclindependent kinase.

Sexual behaviour and stridulation during mating in Triatoma infestans (Hemiptera: Reduviidae)

Factors affecting mating behaviour in the bug Triatoma infestans were quantitatively studied in the laboratory. Experimental conditions were established so that the probability of copulation increased with the time elapsed since the first adult meal. Copulatory attempts by males did not vary as a function of time, but rejections by females became significantly less frequent with the post feeding time. Non-receptive females displayed four types of rejection behaviour, i.e. flattening, stridulation, evasion and abdominal movements. The occurrence of stridulation performed by females in a sexual context was observed in a regular fashion and was quantified for the first time in this species.