Sexual Dimorphism In Traits Research Articles

Genetic variation for sexual dimorphism in developmental traits in Drosophila melanogaster.

Sexual dimorphism in traits of insects during the developmental stages could potentially be the direct or indirect result of sex-specific selection provided that genetic variation for sexual dimorphism is present. We investigated genetic variation in sexual dimorphism in a set of Drosophila melanogaster inbred lines for 2 traits: egg to adult development time and pupation site preference. We observed considerable genetic variation in sexual dimorphism among lines in both traits. The sexual dimorphic patterns remained relatively consistent across multiple trials, despite both traits being sensitive to environmental conditions. Additionally, we measured 2 sexually dimorphic adult morphological traits in 6 sampled lines and investigated correlations in the sexual dimorphism patterns with the 2 developmental traits. The abundance of genetic variation in sexual dimorphism for D. melanogaster developmental traits demonstrated in this study provides evidence for a high degree of evolvability of sex differences in preadult traits in natural populations.

Light and scanning electron imaging confirm sexual dimorphism in scales and anal‐fin rays of the genera Anatolichthys and Paraphanius (Teleostei: Cyprinodontiformes: Aphaniidae)

AbstractThe investigation of secondary sexual dimorphism is a significant and exciting research topic since it has to do with sexual selection, which is connected to selecting a mate and male competitiveness. The purpose of this study was to investigate the microscopic characteristics of scales in several body parts and anal‐fin rays of nine species of the old world cyprinodontiform fishes belonging to the genera Anatolichthys and Paraphanius to find out possible secondary sexual dimorphic traits and their importance in aphaniid taxonomy. Both light and scanning microscopy revealed that scales show general characteristics of aphaniid species and present large cycloid scales of several subtype forms including cycloid‐true circular, cycloid‐chordate, oval‐reversed ovoid, polygonal‐pentagonal, quadrilateral‐square, oval‐ovoid and oval‐oblong in different body parts of fishes. Both genera had sexual dimorphism: (i) male individuals of all nine investigated species presented contact organs in the forms of ctenus‐like structure in the posterior margin of the scales and spicule‐like structure in the anal‐fin rays; (ii) caudal‐fin rays of both sexes lacked contact organs; (iii) the number, position, size and form of contact organs provided a taxonomic signal to identify the two genera; (iv) contact organs can be thought of as functional structures that keep male and female individuals in physical contact during courtship and display behaviour throughout the active phase of reproduction; (v) it can provide evolutionary signals because sexual dimorphism would come from various sexual selection pressures acting on both sexes.

THE PERCEIVED ATTRACTIVENESS OF SEXUAL DIMORPHIC FEATURES IN MALE FACES ACROSS THE LIFESPAN OF A WOMAN

According to evolutionary psychology, the presence of masculine sexual dimorphic traits is an indicator of the hidden qualities of the organism. On the other hand, it is also characteristic of men with low levels of warmth, honesty, and a reluctance to invest in offspring. As female reproductive goals vary across a woman’s lifespan, changing from finding the best donor of “good genes” to a commitment to a “selfless caregiver”, it is probable that the attractiveness of masculine/feminine facial features in male faces changes across a lifespan. The results of the study indicate that the degree of preference for masculine male faces increases from their teens, reaches a maximum during the period of reproduction before marriage and decreases in older age, with a statistically significant decrease in the postmenopausal period.

Cranio-facial bones evaluation based on clinical CT data for sex determination in Northwest Indian population

The skull and pelvis have been the first choice of bones for determination of unknown human remains. The goal of the present study was to derive discriminant function equations by using clinical CT scan data of cranio-facial bones for sex determination in Northwest Indian population. This study was conducted at Department of Radiology, by collecting the retrospective data of CT scan of 217 samples. In the data, 106 were males and 111 were females in the age group between 20 and 80 years. The total number of parameters under investigation were 10. All the selected variables were sexually dimorphic and showed significant values. 91.7% of original grouped cases were correctly classified to their sex category. The TEM, rTEM and R were under the acceptable limits. The univariate, multivariate and stepwise discriminant function analysis recorded an accuracy of 88.9%, 91.7% and 93.6% respectively. Multivariate direct discriminant function analysis stepwise method yielded the highest level of accuracy in differentiating males and females. All the variables reflected statistically significant difference between males and females (p less than 0.001). The best single parameter with highest level of sexual dimorphic trait was length of cranial base. This study aims to provide sex assessment using clinical data of CT scan in Northwest Indian population by incorporating the BIOFB cranio-facial parameter. The morphometric measurements taken on CT scan images can be utilized by forensic experts in identification process.

A Semi-Automatic Method on a Small Italian Sample for Estimating Sex Based on the Shape of the Crown of the Maxillary Posterior Teeth

Teeth are known to be reliable substrates for human identification and are endowed with significant sexual dimorphism not only in the size but also in the shape of the crowns. In the preliminary phase of our study (already published in 2021), a novel sex estimation method based on dental morphometric geometric (GMA) analysis combined with the artificial neural network (ANN) was developed and validated on a single dental element (first upper premolar) with an accuracy rate of 80%. This study aims to experiment and validate the combination of GMA-ANN on the upper first and second left premolars and the upper left first molar to obtain a reliable classification model based on the sexual dimorphic traits of multiple maxillary teeth of Caucasian Italian adults (115 males and 115 females). A general procrustes superimposition (GPS) and principal component analysis (PCA) were performed to study the shape variance between the sexes and to reduce the data variations. The "set-aside" approach was used to validate the accuracy of the proposed ANN. As the main findings, the proposed method correctly classified 94% of females and 68% of males from the test sample and the overall accuracy gained was 82%, higher than the odontometric methods that similarly consider multiple teeth. The shape variation between male and female premolars represents the best dimorphic feature compared with the first upper molar. Future research could overcome some limitations by considering a larger sample of subjects and experimenting with the use of computer vision for automatic landmark positioning and should verify the present evidence in samples with different ancestry.

A Comparison of Feathers and Oral Swab Samples as DNA Sources for Molecular Sexing in Companion Birds.

The early age determinism of the sex in case of monomorphic birds is very important, because most companion birds have no distinct sexual dimorphic traits. Molecular genetic sexing was proved to be one of the most accurate sex determinations in monomorphic birds. The aim of this study was to compare the results obtained by PCR performed on isolate genomic DNA from paired samples of feathers and oral swabs collected from the same individuals. Samples of oral swabs (n = 101) and feathers (n = 74) were collected from 101 companion birds from four different species (Columba livia domestica, Psittacula krameri, Neophema splendida and Agapornis spp.). The PCR was performed for the amplification of the CHD1W and CHD1Z genes in females and the CHD1Z gene in males. The overall PCR success rate of sex determination was significantly higher from oral swabs than from feathers. The PCR success rate from oral swabs was higher in juveniles and from feathers was significantly higher in adults. The similarity between the oral swab and feathers was obtained in 78.38% of the birds. Oral swabs proved to be a more reliable sample for genetic sex determination in the species tested in this study.

Three-dimensional analysis of modeled facial aging and sexual dimorphism from juvenile to elderly age

A detailed understanding of craniofacial ontogenetic development is important in a variety of scientific disciplines dealing with facial reconstruction, forensic identification, ageing prediction, and monitoring of pathological growth, including the effect of therapy. The main goals of this study were (1) the construction of the facial aging model using local polynomial regression fitting separately for both sexes, (2) evaluation of the aging effect not only on facial form as a whole but also on dimensions important for clinical practice, and (3) monitoring of the development of shape facial sexual dimorphism. Our study was based on the form and shape analysis of three-dimensional facial surface models of 456 individuals aged 14–83 years. The facial models were obtained using a structured light-based optical scanner and divided (for some analyses) into four age categories (juveniles, young adults, middle adults, and elderly adults). The methodology was based on geometric and classic morphometrics including multivariate statistics. Aging in both sexes shared common traits such as more pronounced facial roundness reducing facial convexity, sagging soft tissue, smaller visible areas of the eyes, greater nose, and thinner lips. In contrast to female faces, male faces increase in size until almost 30 years of age. After the age of 70, male facial size not only stagnates, like in females, but actually decreases slightly. Sexual dimorphic traits tended to diminish in the frontal and orbitonasal areas and increase in the gonial area.

DNA Sex Identification Using Different Biological Samples from Four Companion Bird Species

Most companion birds have no distinct sexual dimorphic traits. The aim of this study was to identify the CHD genes from sexual chromosomes of birds (ZW) from various tissue samples. Feathers, oral swabs, blood and various tissues (by necropsy) were collected from four companion bird species (Gallus gallus domesticus, Melopsittacus undulatus, Psittacus erithacus, Ara ararauna). Feathers were processed mechanically using the Tissue Lyser II. DNA isolation was performed using the Isolate II Genomic DNA, Bioline kit. PCR was performed according to Griffiths et al. (1998) using P2/P8 primers. Chicken whose DNA sexing was identified based on phenotypic characters, was confirmed by PCR. Budgerigars whose DNA sexing identified a male and female have been confirmed based on necropsy results. African Grey Parrot whose sex was identified by DNA sexing as female was confirmed based on a genetic sexing previously performed. The Blue and Yellow Macaw, whose sex was determined as male by DNA sexing, was confirmed based on necropsy results. DNA concentration was higher in blood samples than in oral swabs or feathers. Blood collection is considered an invasive procedure in birds. For feather samples, mechanical denaturation before DNA extraction is recommended. Oral swab samples are suitable for isolating and amplifying DNA in birds.

Black and orange coloration predict success during male–male competition in the guppy

AbstractInvestigating how intrasexual competition and intersexual mate choice act within a system is crucial to understanding the maintenance and diversity of sexually-dimorphic traits. These two processes can act in concert by selecting for the same trait, or in opposition by selecting for different extremes of the same trait; they can also act on different traits, potentially increasing trait complexity. We asked whether male–male competition and female mate choice act on the same male traits using Trinidadian guppies, which exhibit sexual size dimorphism and male-limited color patterns consisting of different colors arranged along the body and fins. We used behavioral assays to assess the relationship between color and competitive success and then compared our results to the plethora of data on female choice and color in our study population. Males initiated more contests if they were larger than their competitor. Males won contests more often if they had more black coloration than their competitor, and the effect of black was stronger when males had less orange than their competitor. Additionally, males won more often if they had either more structural color (iridescence) and more orange, or less structural color and less orange than their competitor, suggesting multiple combinations of color traits predict success. Females from our study population exhibit a strong preference for more orange coloration. Thus, traits favored in male contests differ from those favored by intersexual selection in this population. These results suggest that inter- and intrasexual selection, when acting concurrently, can promote increased complexity of sexually selected traits.

Sex-biased proteomic response to tomato spotted wilt virus infection of the salivary glands of Frankliniella occidentalis, the western flower thrips

Successful transmission of tomato spotted wilt virus (TSWV) by Frankliniella occidentalis requires robust infection of the salivary glands (SGs) and virus delivery to plants during salivation. Feeding behavior and transmission efficiency are sexually-dimorphic traits of this thrips vector species. Proteins secreted from male and female SG tissues, and the effect of TSWV infection on the thrips SG proteome are unknown. To begin to discern thrips factors that facilitate virus infection of SGs and transmission by F. occidentalis, we used gel- and label-free quantitative and qualitative proteomics to address two hypotheses: (i) TSWV infection modifies the composition and/or abundance of SG-expressed proteins in adults; and (ii) TSWV has a differential effect on the male and female SG proteome and secreted saliva. Our study revealed a sex-biased SG proteome for F. occidentalis, and TSWV infection modulated the SG proteome in a sex-dependent manner as evident by the number, differential abundance, identities and generalized roles of the proteins. Male SGs exhibited a larger proteomic response to the virus than female SGs. Intracellular processes modulated by TSWV in males indicated perturbation of SG cytoskeletal networks and cell-cell interactions, i.e., basement membrane (BM) and extracellular matrix (ECM) proteins, and subcellular processes consistent with a metabolic slow-down under infection. Several differentially-abundant proteins in infected male SGs play critical roles in viral life cycles of other host-virus pathosystems. In females, TSWV modulated processes consistent with tissue integrity and active translational and transcriptional regulation. A core set of proteins known for their roles in plant cell-wall degradation and protein metabolism were identified in saliva of both sexes, regardless of virus infection status. Saliva proteins secreted by TSWV-infected adults indicated energy generation, consumption and protein turnover, with an enrichment of cytoskeletal/BM/ECM proteins and tricarboxylic acid cycle proteins in male and female saliva, respectively. The nonstructural TSWV protein NSs - a multifunctional viral effector protein reported to target plant defenses against TSWV and thrips - was identified in female saliva. This study represents the first description of the SG proteome and secretome of a thysanopteran and provides many candidate proteins to further unravel the complex interplay between the virus, insect vector, and plant host.

Sex and male breeding state predict intraspecific trait variation in mouth-brooding fishes.

Sex‐specific reproductive roles contribute to sexual dimorphic morphological trait variations. In uniparental mouth‐brooding fishes, the mouth performs a reproductive function in addition to its key roles in feeding and respiration, resulting in the potential for sex‐specific functional performance trade‐offs. Trait differences related to parental care may occur when the individual matures or be restricted to periods when the parent is mouth‐brooding. This study explored sexual dimorphism and morphological trait adaptations related to feeding, breeding, respiration and locomotion performance in two paternal mouth‐brooding freshwater fishes (Glossamia aprion and Neoarius graeffei). Eight morphological traits were evaluated for sexual dimorphism (non‐brooder males vs. females) and male breeding state differences (brooders vs. non‐brooders). Male breeding state was a significant predictor of trait variation in both species. Brooders differed in buccal volume and in several feeding and locomotory traits compared to non‐brooder males. Non‐brooder males had bigger buccal volumes and relative eye diameters (G. aprion) and larger relative gape sizes (N. graeffei) compared to females, a potential response to both mouth‐brooding and feeding requirements. Although there were clear trait differences between brooder and non‐brooder males, further research is required to confirm whether individuals return to their former morphology once mouth‐brooding has ceased or if trait differences are maintained post‐brooding. This study highlights the importance of considering the potential impacts of intraspecific trait variation on the performance of critical life functions, such as feeding, respiration and locomotion across the life history.

Morphometric Analysis of Orbital Cavity in South Indian Population

Introduction: Each orbital cavity is actually meant as a socket for the eyeball. The human orbit is a complicated anatomic area, which performs predominant position in the craniofacial complex.
 Aim: The aim of the study is to provide the normal reference orbital parameters for the south Indian population.
 Materials and Methods: The present study has adopted 30 south Indian dry skulls. An orbital cavity was measured using vernier callipers. With the help of vernier calliper and ruler, the measurements such as length, breadth of the orbital cavity and biorbital breadth, interorbital breadth of the orbital cavity were measured. The paired t-test is the statistical method used in this study.
 Results: The mean orbital breadth of the right orbit is 34.6±1.777 and left orbit was 34.701±1.711
 The mean orbital height of the right orbit is 33.417±1.494 and the left orbit is 33.38±1.560. The mean biorbital breadth of the orbital cavity is 94.16 ± 2.533 and means interorbital breadth of the orbital cavity is 20.615±1.172. Paired t test demonstrated no significant statistical difference between the right and left orbit.
 Conclusion: The orbital cavity additionally used for determination of sex and ethnic courses of a cadaver and its phase of the cranium that posses manipulate over sexual dimorphic traits.

Comparative Evaluation Of Two Techniques Of Sex Determination In Lovebirds (Agapornis Spp.)

Most lovebirds (Agapornis spp.) have no distinct sexual dimorphic traits. The objective of the paper was to compare the results of two sexing methods, surgical sexing by celioscopy and DNA sexing by PCR from blood samples, in order to evaluate their effectiveness. Materials used to carry out the studies were a 2.7 mm telescope and endoscopy unit, surgical instruments and DNA sampling kits provided by Exomed.cz laboratory. Forty-two lovebirds were included in this study. The endoscopic sexing procedure was performed by the method described by Divers. Blood sampling for DNA testing by PCR method was performed from the metatarsal vein. The results were different in the case of one lovebird, endoscopic sexing revealed it as male, compared to DNA testing, where it was identified as female. DNA sexing is a non-invasive method that might be more accurate than celioscopy in this species, and bird owners have easier access to it.

Experimentally induced intrasexual mating competition and sex-specific evolution in female and male nematodes.

Sexual dimorphism in life history traits and their trade‐offs is widespread among sexually reproducing animals and is strongly influenced by the differences in reproductive strategies between the sexes. We investigated how intrasexual competition influenced specific life history traits, important to fitness and their trade‐offs in the outcrossing nematode Caenorhabditis remanei. Here, we altered the strength of sex‐specific selection through experimental evolution with increased potential for intrasexual competition by skewing the adult sex ratio towards either females or males (1:10 or 10:1) over 30 generations and subsequently measured the phenotypic response to selection in three traits related to fitness: body size, fecundity and tolerance to heat stress. We observed a greater evolutionary change in females than males for body size and peak fitness, suggesting that females may experience stronger net selection and potentially harbour higher amounts of standing genetic variance compared to males. Our study highlights the importance of investigating direct and indirect effects of intrasexual competition in both sexes in order to capture sex‐specific responses and understand the evolution of sexual dimorphism in traits expressed by both sexes.

Digit identity matters: origin and evolution of sexual dimorphism in the digit lengths of tropidurid lizards

AbstractSexual dimorphism in digit lengths reflects phenotypic evolution mediated by developmental steroids. Differences in the identity of the sexually-dimorphic digit may evolve if the concentrations of sex-steroid receptors in the digit are easily modified and the initial changes have low impact on fitness. Accordingly, sexual dimorphism in digit lengths might initially originate under neutral selective regimes, being subsequently co-opted by embryonic hormonal effects on sensitive traits that are more likely to be targeted by selection. Correlated variation among sexually-dimorphic traits might therefore reflect pleiotropic hormonal modulation during development. Moreover, the identity and trend of the sexually-dimorphic digit might be evolutionarily labile even among closely-related species. We evaluated this model by assessing the identity of sexually-dimorphic digits among 11 Tropiduridae lizard species and inferring evolutionary patterns of sexual dimorphism. Assuming that digit lengths can be used as a proxy for hormonal modulation of steroid-sensitive traits during development, we tested for evolutionary associations among sexual dimorphism of digit lengths, body size and other traits that may be direct targets of sexual selection in the Tropiduridae. Sexual dimorphism in digit lengths is evolutionarily labile in the Tropiduridae, and diversity, instead of conservatism, seems to rule developmental mechanisms underlying the evolution of sexual dimorphism in digit ratios.

Interspecific allometry for sexual shape dimorphism: Macroevolution of multivariate sexual phenotypes with application to Rensch's rule.

Allometric trends in the degree of sexual dimorphism with body size have long fascinated evolutionary biologists. Many male-biased clades display more prominent sexual dimorphism in larger taxa (Rensch's rule), with most examples documenting this pattern for body size dimorphism. Although sexual dimorphism in traits other than body size is equally functionally relevant, characterizing allometric patterns of sexual dimorphism in such traits is hampered by lack of an analytical framework that can accommodate multivariate phenotypes. In this article, we derive a multivariate equivalency for investigating trends in sexual dimorphism-relative to overall body size-across taxa and provide a generalized test to determine whether such allometric patterns correspond with Rensch's rule. For univariate linear traits such as body size, our approach yields equivalent results to those from standard procedures, but our test is also capable of detecting trends in multivariate datasets such as shape. Computer simulations reveal that the method displays appropriate statistical properties, and an empirical example in Mediterranean lizards provides the first demonstration of Rensch's rule in a multivariate phenotype (head shape). Our generalized procedure substantially extends the analytical toolkit for investigating macroevolutionary patterns of sexual dimorphism and seeking a better understanding of the processes that underliethem.

Extreme and Variable Climatic Conditions Drive the Evolution of Sociality in Australian Rodents.

Climate change is generating an intensification of extreme environmental conditions, including frequent and severe droughts [1] that have been associated with increased social conflict in vertebrates [2-4], including humans [5]. Yet, fluctuating climatic conditions have been shown to also promote cooperative behavior and the formation of vertebrate societies over both ecological and evolutionary timescales [6]. Determining when climatic uncertainty breeds social discord or promotes cooperative living (orboth) is fundamental to predicting how species will respond to anthropogenic climate change. In light of this, our limited understanding of the order of evolutionary events-that is, whether harsh environments drive the evolution of sociality [6] or, alternatively, whether sociality facilitates the invasion of harsh environments [7]-and of how cooperation and conflict coevolve in response to environmental fluctuation represent critical gaps in knowledge. Here, we perform comparative phylogenetic analyses on Australian rodents (Muridae: Hydromyini) and show that sociality evolves only under harsh conditions of low rainfall and high temperature variability and never under relatively benign conditions. Further, we demonstrate that the requirement to cooperate under harsh climatic conditions generates social competition for reproduction within groups (reflected in the degree of sexual dimorphism in traits associated with intrasexual competition [8]), which in turn shapes the evolution of body size dimorphism. Our findings suggest that as the environment becomes more severe [1], the resilience of some species may hinge on their propensity to live socially, but in so doing, this is likely to affect the evolution of traits that mediate social conflict.

On a remarkable sexual dimorphic trait in the Characiformes related to the olfactory organ and description of a new miniature species of Tyttobrycon Géry (Characiformes: Characidae).

Among the order Characiformes, secondary sexual dimorphism is commonly associated to the occurrence of bony hooks on fins, shape and length of the dorsal and anal fins, and sexual dichromatism. The analysis of a new miniature Characidae species of the genus Tyttobrycon, described herein, yielded to the discovery of a sexually dimorphic trait related to nostril aperture and number of olfactory lamellae. In this type of dimorphism, mature males present larger nostril aperture and higher number of olfactory lamella than females. A dimorphic olfactory organ is for the first time recorded and described for a member of the Characiformes. Gross morphology and development of brain and peripheral olfactory organ of Tyttobrycon sp. n. are described and compared to other species of Characidae. It is hypothesized that such dimorphic trait is related to male-male detection during cohort competition in small characids. The new species of Tyttobrycon is diagnosed from its congeners by the number of branched anal-fin rays (19–21) and the absence of a caudal-peduncle blotch. It occurs in a small tributary of Rio Madeira basin, near to the limit between Brazil and Bolivia, Acre State, Brazil.

The goby Lythrypnus pulchellus is a bi-directional sex changer

Sex change in both directions is a novelty reported in some species of fishes belonging to seven families associated to reefs. This study demonstrated that Lythrypnus pulchellus, a small cryptobenthic haremic reef fish, is a bi-directional sex changer, at least in experimental conditions. The influence of body size in duration and direction of sex reversal was tested, and the changes of sexual dimorphic traits (elongated anterior dorsal spine, genital papillae, body size) and sex-cell allocation in the gonad during sex change were described. Unisex pairs of individuals, male-male and female-female of similar and different body size, were housed in aquaria recording the changes until spawning. Sex change duration showed no significant differences between protogyny (11 days) and protandry (12 days), regardless of their size. Among pairs of males of different size, the smaller individual changes sex to female whilst among pairs of females of different size larger individuals change sex to male. Among pairs of males of similar size, dominant individuals remained as male whilst subordinate individual did change sex to female. If the pair of similar size were females, the dominant individual changed sex to male whilst the subordinate remained as female. The gonads, before, throughout, and after sex change, showed that females and males contained both ovarian and testicular tissues in different ratios. The length/width ratio of the genital papilla probed to be useful to predict functional sex of individuals. The results support the idea that extreme sexual plasticity is a widespread reproductive trait in the genus Lythrypnus.

Knappach Toll, Balbridie: a late 3rd-millennium bc Beaker burial on Deeside, Aberdeenshire

A short cist discovered during ploughing at Knappach Toll on Balbridie Farm, Aberdeenshire held the remains of an adult accompanied by a Beaker, fragments of a copper awl and 11 struck flints. Little survived of the skeleton except for cranial fragments, but these indicate that the person had been placed with the head to the west, with the artefacts also at that end. While the sex of the person is indeterminate, with the single surviving sexual dimorphic trait suggesting a male, the position of the body and the presence of the awl are more usually indicative of a female. Radiocarbon dating shows that the person died between 3775±35 years bp (SUERC-30852) and 2330–2040 cal bc (95.4% probability). Stable isotope analysis indicates that he or she grew up on basalt geology, like that of the region, or on chalk. Residue analysis of the Beaker has established that it had held ruminant animal fat such as butter or milk, probably for some time, and some of the flint pieces had been lightly used. The composition and constituents of the burial suggest links between north-east Scotland and East Yorkshire. They also evoke the cultural practices that were spreading across eastern Britain in the later 3rd millennium bc through the mechanisms of cultural transmission and migration.