Sex-related Variation Research Articles

Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

AbstractThe franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squidDoryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

Sex-related and spatial variation in trace elements in feathers of the Kentish plover (Charadrius alexandrinus) from different coastal areas of the Iberian Peninsula

This study investigated the sex-related and spatial variation in trace elements concentrations in feathers of the Kentish plover (Charadrius alexandrinus) inhabiting different coastal locations in the Iberian Peninsula. Feathers were sampled in a total of 50 breeding birds from 7 different locations: 3 on the Mediterranean coast (n=18), 1 on the Atlantic coast of Andalusia (n=9) and 3 on the NW Atlantic coast (n=23). The feathers were analyzed to determine the concentrations of Al, Cr, Mn, Cu, Zn, As, Se, Cd, Hg and Pb. All of the trace elements were present at detectable concentrations, and the mean concentrations of Al, Zn and Cu were highest of those considered. The coastal section had a significant effect on 5 elements (Mn, Cu, As, Cd and Pb). The mean concentrations of almost all of the trace elements were highest in the birds from Andalusia, intermediate in the birds from the Mediterranean area and, in general, lowest in the birds from the NW Atlantic coast. Females showed significant higher Mn concentrations and high levels of exogenous elements (Al and As) in contrast with males. Less preening activity during the day of female birds, when they are occupied in incubating eggs, could favour higher concentrations of exogenous trace elements. The high levels of several trace elements observed in the samples from Mediterranean and Atlantic coast of Andalusia may pose a serious threat to these populations.

Sex-related interannual plasticity in wing morphological design in Heliconius charithonia enhances flight metabolic performance.

Flight morphological variations and its consequences on animal performance are common in winged insects. In the butterfly Heliconius charithonia, sex-related differences in the wing morphological design have been described resulting in differences in foraging behavior, daily flight distances and flight aerodynamics. It has been suggested that these differences should be reflected in the metabolic capacities and energetic budgets associated with flight in both sexes. In this study, we analyzed the relationship between wing morphological variation and metabolic performance, flight aerodynamics and energetic reserves in females and males of Heliconius charithonia over two years. The results confirm the presence of wing shape sexual dimorphism, but also show an unexpected sex-related annual variation in wing shape, mirrored in the metabolic condition (resting metabolic rate) of individuals. However, contrary to expectation, intersexual variations in wing shape are not related to differences between the sexes in terms of flight aerodynamics, flight metabolic rates, or energetic reserves (carbohydrates, lipids and proteins). Our results indicate a considerable plasticity in H. charithonia wing shape, which we suggest is determined by a trade-off between environmental pressures and reproductive restriction of each sex, maintaining an optimum flight design. Finally, similarities in metabolic rates between young and older males and females in both years may be a consequence of the ability of Heliconius species to feed on pollen.

The Neanderthal mandible BD 1 from La Chaise-de-Vouthon Abri Bourgeois-Delaunay (Charente, Southwestern France, OIS 5e). Dental tissue proportions, cortical bone distribution and endostructural asymmetry

The 23 fossil human remains found at La Chaise-de-Vouthon Abri Bourgeois-Delaunay (Charente, Southwestern France) are all attributed to Neanderthals. The BD 1 mandible represents one of the best preserved specimens recovered in this assemblage, still bearing the entire set of 16 teeth, and attributed to an adult - likely 20-35 years old –individual. The geochronological and paleontological data indicate that the Neanderthals from Abri Bourgeois-Delaunay lived in a temperate environment between 127 and 116 ka (i.e., during the OIS 5e). In this study, we integrate and expand the morphometric record of BD 1 by quantifying the tissue proportions of its entire permanent dentition, including radicular thickness repartition of four front teeth, and comparing its degree of endostructural asymmetry in tooth tissue organization and postcanine cortical bone topography with the patterns shown by Regourdou 1. Our results show that crown and radicular dental internal signature is typically Neanderthal, comparable with the available data for Regourdou 1, and is unambiguously distinct from the fossil and extant modern human patterns. Asymmetry in tooth tissue proportions in BD 1 and Regourdou 1 is clearly non-directional, as side dominance is nearly equally distributed between the left and the right antimeres. Similarly, both Neanderthal mandibles show no marked cortical bone asymmetry at the molar level, even if a slight right dominance is found in BD 1. Even if these results are globally consistent for the two Neanderthal mandible, extensive methodological research on the patterns of age- and sex-related endostructural variation displayed by human population samples from diverse chrono-geographic, socio-economic and biocultural contexts is still needed to more confidently evaluate the evolutionary and adaptive significance of the signals from the fossil record.

Testing the greater male variability phenomenon: male mountain chickadees exhibit larger variation in reversal learning performance compared with females.

The greater male variability phenomenon predicts that males exhibit larger ranges of variation in cognitive performance compared with females; however, support for this pattern has come exclusively from studies of humans and lacks mechanistic explanation. Furthermore, the vast majority of the literature assessing sex differences in cognition is based on studies of humans and a few other mammals. In order to elucidate the underpinnings of cognitive variation and the potential for fitness consequences, we must investigate sex differences in cognition in non-mammalian systems as well. Here, we assess the performance of male and female food-caching birds on a spatial learning and memory task and a reversal spatial task to address whether there are sex differences in mean cognitive performance or in the range of variation in performance. For both tasks, male and female mean performance was similar across four years of testing; however, males did exhibit a wider range of variation in performance on the reversal spatial task compared with females. The implications for mate choice and sexual selection of cognitive abilities are discussed and future directions are suggested to aid in the understanding of sex-related cognitive variation.

Sex-related variation in the dimensions of the mandibular ramus and its relationship with lower third molar impaction

ObjectiveWe conducted this study to assess possible sex-related variations in the dimensions of the mandibular ramus. MethodsWe divided 240 patients into two groups: an impacted lower third molar group of 115 subjects (68 men and 47 women) and a normally erupted lower third molar group of 125 subjects (89 men and 36 women). ResultsThe study identified multiple sex-related differences between impacted and normally erupted lower molar groups. Men demonstrated greater values in the majority of variables compared to women. Furthermore, men in both the impacted and control groups had greater condylar length, coronoid process length, ramus height, ramal width, retromolar space, and retromolar space ratio than women. By contrast, women in both groups had a larger gonial angle, more upright lower posterior teeth, and more upright impaction than men. Both sexes in the control group had larger values for most measurements than their counterparts in the impacted group. Women in both groups had more upright posterior teeth and less inclined third molars. ConclusionIn our study, men had greater values for most of the analysed variables compared to women. Configuration of the mandibular ramus is related to the sex, which might enhance the probability of third molar eruption or impaction.

A structural biorhythm related to human sexual dimorphism

Life on earth is regulated by biological rhythms, some of which oscillate with a circadian, monthly or lunar cycle. Recent research suggests that there is a near weekly biorhythm that may exert an influence on human skeletal growth. Evidence for the timing of this biorhythm is retained in tooth enamel as the periodicity of Retzius lines. Studies report that Retzius periodicity (RP) relates to adult human stature and enamel thickness. Adult human stature is sexually dimorphic, and so is enamel thickness of maxillary third molars (M3) but not mandibular M3. Yet, previous studies report sex differences in RP are apparent in some populations but not others, and it is unknown if dimorphism in enamel thickness relates to RP. To further our understanding of this biorhythm we analysed sex-related variation in RP and its relationship with enamel thickness in a sample of M3′s (n = 94) from adults in Northern Britain. Results reveal RP was significantly higher in our sample of female molars compared to those of males, which is consistent with the previously reported correlation between the biorhythm and adult stature. The RP of maxillary M3 related to sex differences in enamel thickness, but this relationship was not present in mandibular M3. Our results support previous findings suggesting that this biorhythm is sexually dimorphic and provide the first evidence that RP may be one factor influencing sex differences in enamel thickness. Our study also shows that correlations between RP and enamel thickness appear to be most readily detected for tooth types with sufficiently wide ranges of enamel thickness variation, as is the case for maxillary but not mandibular M3. Achieving a sufficient sample size was critical for detecting a sex difference in periodicity.

Sex-Related Spatial Variation in the Heterophil-To-Lymphocyte Ratio of Breeding Great Tits Parus major

Enduring changes in the surrounding environment cause long-term stress in birds, which can affect the activity of the immune system and lead to changes in heterophil-to-lymphocyte ratios (H:L). The aim of this paper is to investigate if the H:L ratios of male and female Great Tits Parus major during the first breeding attempt differ between two sites of dissimilar habitats – an urban parkland site and a deciduous forest site. In the final model we found a difference between sites, while separate submodels for the study sites showed that females had higher H:L ratio than males in the urban parkland site, with the opposite result being found in the forest site. We suppose that the pattern of variation in H:L ratios we found may result from greater parental expenditures of females as compared to males. Such difference in the H:L ratio between habitats could be the reason for the substantial difference in trophic conditions between the forest and park areas during the breeding of tits.

Interspecific size- and sex-related variation in the cranium of European brown frogs (Genus Rana)

The vertebrate skull is considered as phylogenetically conserved, but shows extensive diversification in many clades due to various environmental, climate and habitat influences. We explored the cranial size and shape differences of three closely related brown frog species, Rana temporaria, R. dalmatina and R. graeca to emphases the interspecific variation and intraspecific sexual differences, the allometric patterns in cranial shape changes and the relationship between cranial shape, phylogeny, and ecological similarity. Brown frogs significantly differ in cranial size and shape. Interspecific cranial shape changes are under strong influence of size variation. When size is considered, our results show that R. dalmatina is the most divergent species, while differences between R. dalmatina and R. temporaria cranial shapes are diminished when size is removed and peculiar features of R. graeca cranium arise (the most robust and rounded cranium). In both cases, with size and without size, major shape changes are related to the position of quadratum and width of the cranium at the level of anterior margin of eye. When comparing non-allometric shape with ecological similarity and phylogenetic relatedness we found that ecologically similar but phylogenetically more distant species shared the cranial morphology. Intraspecific patterns of cranial phenotypic variation in brown frogs showed significant cranium sexual size and shape dimorphism and absence of allometric scaling between sexes. More detailed studies on the relation of morphology and ecology in brown frogs are necessary to explain the mechanism behind cranial size and shape variation.

Feeding ecology of the Kızılırmak toothcarp, Aphanius marassantensis: ontogenetic shift and seasonal diet variation

We studied the feeding ecology of an endemic cyprinodontid fish, Aphanius marassantensis (Kizilirmak Toothcarp), with special emphasis on seasonal and ontogenetic diet shift. The dietary composition revealed an omnivorous diet with great seasonal and ontogenetic variation. Cladocera and Calanoid Copepods (Diaptomus sp.) dominated the diet in Spring and Summer, whereas the food items of plant origin e.g. filamentous algae and diatoms were the most important components in Autumn and Winter. An ontogenetic diet shift was also demonstrated. While the feeding of juveniles was based mostly on planktonic organisms, adult individuals preferred larger prey taxa, such as Gammarus sp. and Gastropods. There was no significant sex-related variation in feeding with the exception for the volume of gut content. The investigation on the feeding strategy of A. marassantensis suggested a generalised feeding pattern with some specialised individuals. This generalist feeding habits may account for the well-established population of this species in a big reservoir under coexistence of two non-native fish species, Pseudorasbora parva and Atherina boyeri.

Drivers of wing shape in a widespread Neotropical bird: a dual role of sex-specific and migration-related functions

A large body of research has shown how avian morphology is shaped by specific behavioral repertoires and life history traits. Yet, the majority of such research has been conducted on birds breeding at north-temperate latitudes. We tested the hypothesis that functional wing traits of Fork-tailed Flycatchers (Tyrannus savana), which migrate within South America, vary predictably between non-migratory and migratory flycatchers. Additionally, due to sex-specific differences in this species (e.g., males perform courtship displays), we explored sex-related variation in wing shape. We applied classic measures of wing shape (e.g., wing loading, length, aspect ratio, pointedness), as well as landmark-based morphometric analysis to describe the wing morphology of Fork-tailed Flycatchers from breeding populations across South America. We found that migratory flycatchers tend to have more pointed wings than non-migratory flycatchers. Additionally, we found that males have wings that are significantly longer, more pointed, with a higher aspect ratio and that are more swept than those of females, regardless of whether they migrate or not. Overall, our results suggest that wing shape of Fork-tailed Flycatchers is the result of a complex set of tradeoffs shaped by selective pressures exerted on both sexes (i.e., the need to forage on the wing, evade predators and migrate efficiently), as well as sex-specific behaviors (e.g., the need for males to execute acrobatic displays).

Sex-related variation of neurocognitive functioning in bipolar disorder: Focus on visual memory and associative learning

Bipolar disorder (BD) is associated with cognitive deficits in attention, verbal memory and executive functions. However, only few studies have examined sex effects on cognition despite their clinical relevance. Given that visual memory/ learning has been understudied the aim of our study was to investigate sex-related variation in cognition (executive functions and visual memory/ learning) in BD. Cognitive performance of 60 bipolar-I patients and 30 healthy controls was evaluated by using CANTAB battery tasks targeting spatial memory (SRM), paired associative learning (PAL) and executive functions. We fitted a multivariate analysis of covariance (MANCOVA), followed by task-specific ANCOVAs. A significant diagnosis by sex interaction effect was detected (MANCOVA); specifically, diagnosis-specific sex effects were found for SRM and PAL, as healthy males outperformed healthy females but this pattern was attenuated in BD patients. Patients' clinicodemographic characteristics, current psychopathology or medication status did not differ across sexes and were, therefore, unlikely to explain detected sex effects. Our study is one of few studies to assess sex-related variation in cognition in BD and the first to record a diagnosis-specific sex effect for two tasks of visuo-spatial memory/ learning, indicating that sex-related variation in healthy subjects is disrupted in BD.

Associations of physical strength with facial shape in an African pastoralist society, the Maasai of Northern Tanzania.

ObjectivesPrevious research has documented associations of physical strength and facial morphology predominantly in men of Western societies. Faces of strong men tend to be more robust, are rounder and have a prominent jawline compared with faces of weak men. Here, we investigate whether the morphometric patterns of strength-face relationships reported for members of industrialized societies can also be found in members of an African pastoralist society, the Maasai of Northern Tanzania.Materials and methodsHandgrip strength (HGS) measures and facial photographs were collected from a sample of 185 men and 120 women of the Maasai in the Ngorongoro Conservation Area. In young-adults (20–29 years; n = 95) and mid-adults (30–50 years; n = 114), we digitized 71 somatometric landmarks and semilandmarks to capture variation in facial morphology and performed shape regressions of landmark coordinates upon HGS. Results were visualized in the form of thin-plate plate spline deformation grids and geometric morphometric morphs.ResultsIndividuals with higher HGS tended to have wider faces with a lower and broader forehead, a wider distance between the medial canthi of the eyes, a wider nose, fuller lips, and a larger, squarer lower facial outline compared with weaker individuals of the same age-sex group. In mid-adult men, these associations were weaker than in the other age-sex groups.DiscussionWe conclude that the patterns of HGS relationships with face shape in the Maasai are similar to those reported from related investigations in samples of industrialized societies. We discuss differences between the present and related studies with regard to knowledge about the causes for age- and sex-related facial shape variation and physical strength associations.

Investigating the sex-related geometric variation of the human cranium.

Accurate sexing methods are of great importance in forensic anthropology since sex assessment is among the principal tasks when examining human skeletal remains. The present study explores a novel approach in assessing the most accurate metric traits of the human cranium for sex estimation based on 80 ectocranial landmarks from 176 modern individuals of known age and sex from the Athens Collection. The purpose of the study is to identify those distance and angle measurements that can be most effectively used in sex assessment. Three-dimensional landmark coordinates were digitized with a Microscribe 3DX and analyzed in GNU Octave. An iterative linear discriminant analysis of all possible combinations of landmarks was performed for each unique set of the 3160 distances and 246,480 angles. Cross-validated correct classification as well as multivariate DFA on top performing variables reported 13 craniometric distances with over 85% classification accuracy, 7 angles over 78%, as well as certain multivariate combinations yielding over 95%. Linear regression of these variables with the centroid size was used to assess their relation to the size of the cranium. In contrast to the use of generalized procrustes analysis (GPA) and principal component analysis (PCA), which constitute the common analytical work flow for such data, our method, although computational intensive, produced easily applicable discriminant functions of high accuracy, while at the same time explored the maximum of cranial variability.

Modelling neuroanatomical variation during childhood and adolescence with neighbourhood-preserving embedding

Brain development is a dynamic process with tissue-specific alterations that reflect complex and ongoing biological processes taking place during childhood and adolescence. Accurate identification and modelling of these anatomical processes in vivo with MRI may provide clinically useful imaging markers of individual variability in development. In this study, we use manifold learning to build a model of age- and sex-related anatomical variation using multiple magnetic resonance imaging metrics. Using publicly available data from a large paediatric cohort (n = 768), we apply a multi-metric machine learning approach combining measures of tissue volume, cortical area and cortical thickness into a low-dimensional data representation. We find that neuroanatomical variation due to age and sex can be captured by two orthogonal patterns of brain development and we use this model to simultaneously predict age with a mean error of 1.5–1.6 years and sex with an accuracy of 81%. We validate this model in an independent developmental cohort. We present a framework for modelling anatomical development during childhood using manifold embedding. This model accurately predicts age and sex based on image-derived markers of cerebral morphology and generalises well to independent populations.

Morphological Analysis of Healthy Aortic Arch

This study aimed to describe an arch morphology protocol in a healthy population, and to assess the impact of age and sex. A retrospective morphology evaluation was conducted in a population with no personal history of thoracic aorta surgery or pathology, through computed tomography (CT) imaging analysis, using a standardised protocol. Based on centreline three dimensional coordinates, a single investigator calculated a series of parameters in the arch zones and in the total arch, using Matlab scripts. These were categorized as: (i) morphometric data: diameter, length and aortic angle of each zone, total arch angle, and length; (ii) geometric data: tortuosity index (TI), arch width, assimilated curvature radius (CRi), and attachment zone angles. Student or Mann-Whitney tests were used to compare parameter means. Their variability with age and sex was assessed through univariate and multivariate regression analysis. CT images from 123 subjects (mean±SD age 53±19 years) were reviewed. Significant correlation between age and morphology was found. The aorta expanded homogeneously and stretched heterogeneously with age because of posterior arch elongation. TI decrease, CRi, and attachment zone angle increase were also observed with aging. Age remained significantly associated with these morphological parameters, independently of body surface area and hypertension. Sex also affected morphology: longer total arch length and higher CRarch in men; lower zone 3 attachment angle in women CONCLUSION: Using mathematical algorithms, and with a view to improving endovascular arch treatment, this study provides a standardised arch morphology protocol and objectively identifies both age related evolution and sex related variation in the different zones.

Spatial, temporal, age, and sex related variation in the diet of South American sea lions in southern Chile

AbstractWe analyzed spatial, temporal, and age/sex variation in the diet of the South American sea lions (SASL, Otaria byronia) in southern Chile via δ13C and δ15N isotope analysis, with emphasis on exotic farmed and feral salmonids as a source of prey for this generalist predator. Isotope mixing models show that the primary prey consumed by SASL were demersal and benthopelagic fishes. Individuals sampled in summer and in the outer coast had higher δ15N values than those from winter or from the inner coast due to consumption of high trophic level demersal fish. We also found evidence of an ontogenetic shift in isotopic niche width as measured by δ13C and δ15N standard ellipse areas, with juveniles showing a restricted isotopic niche width (1.0‰2) in comparison to subadult (2.2‰2) and adult males (1.9‰2). The proportion of salmonids in the diet of the SASL was negligible and lower than reported in previous studies, which may be related to a recent drop in the production of salmon aquaculture in the region. Our study suggests that the SASL are able to adapt to shifts in spatiotemporal variations in the abundance of potential prey, including feral and farmed salmonids.

Defining Health Trajectories in Older Adults With Five Clinical Indicators.

Background:People age differently, challenging the identification of those more at risk of rapid health deterioration. This study aimed to explore the heterogeneity in the health of older adults by using five clinical indicators to detect age-related variation and individual health trajectories over time.Methods:Health of 3,363 people aged 60+ from the Swedish National study on Aging and Care-Kungsholmen (SNAC-K) assessed at baseline and at 3- and 6-year follow-ups. Number of chronic diseases, physical and cognitive performance, personal and instrumental activities of daily living were integrated in a health assessment tool (HAT). Interindividual health differences at baseline and follow-ups were assessed with logistic quantile regression. Intraindividual health trajectories were traced with quantile mixed-effect models.Results:The HAT score ranges from 0 (poor health) to 10 (good health); each score corresponds to a specific clinical profile. HAT was reliable over time and accurately predicted adverse health outcomes (receiver-operating characteristic areas: hospitalization = 0.78; 95% confidence interval = 0.74–0.81; mortality = 0.85; 95% confidence interval = 0.83–0.87; similar areas obtained for gait speed). Before age 85, at least 90% of participants were free of severe disability, and at least 50% were functionally independent despite chronic disorders. Age- and sex-related variation and high heterogeneity in health were detected at baseline and confirmed by intraindividual health trajectories.Conclusions:This study provides a positive picture of the health status of people 60+. Despite the complexity and heterogeneity of health in this age group, we could identify age- and sex-specific health trajectories using an integrated HAT. HAT is potentially useful in clinical practice and public health interventions.

The ecology of the red fox (Vulpes vulpes L.) in the middle Lena River basin

The population of foxes in the central regions of Yakutia has grown by a factor of four to five during the period from 2000 to 2011–2012, following an increase in the abundance of voles from the genus Microtus. A total of 130 carcasses of foxes taken in 2007–2012 have been examined. Age- and sex-related variation in morphological features has been described. The demographic structure of the population has been studied by estimating animal age from annual layers in the recording structures. Changes in female fertility and involvement in reproduction depending on age and feeding conditions have been analyzed. Changes in the composition of fox diet caused by long-term population depression in the mountain hare and their effect on the dynamics of fox abundance have been revealed. Age- and sex-related characteristics of the condition factor in foxes and sex-related differences in their dietary preferences have been demonstrated.

Age- and sex-related variation in defensive secretions of adult Chlaenius cordicollis and evidence for their role in sexual communication

Defensive secretions of adult Chlaenius cordicollis (Coleoptera: Carabidae) from Manitoba and Pennsylvania were analyzed across the life cycle in a multi-year study using solid phase microextraction and gas chromatography-mass spectrometry. In concurrent experiments using Y-tube olfactometry, we observed the response of each sex when male or female source beetles were induced to discharge defensive secretions. Almost all defensive secretion samples contained five alkylphenolic compounds, dominated by 3-methylphenol; frequently, two alkoxyphenolic compounds and one ester were also detected. As beetles aged, the composition of their defensive secretion shifted, showing an exponential decrease in the relative proportion of 2,3-dimethylphenol as a function of day of year. Previously reported differences observed in autumn between secretions of beetles from Manitoba and Pennsylvania are attributable to different times of onset of the decline of 2,3-dimethylphenol in the two locales. Regardless of airborne odor, responding beetles exhibited upwind anemotaxis in the olfactometer and, outside of the reproductive period, avoidance was the most frequent response to defensive secretions. Sexual dimorphism was evident in the major components of the defensive secretions during the reproductive period and resulted from an increase over time in 2,5-dimethylphenol in male beetles. In the reproductive period, neither sex avoided odor from male source beetles, females preferred clean air to odor from source females, and males were attracted to females that discharged defensive secretion but showed no preference when females had not discharged the secretion. The defensive secretion appears to function as a sex attractant during the reproductive period.