Sex Differences In Size Research Articles

Age- and size-related changes in hind limb muscles in two baboon species (Papio anubis and P. papio).

Body size has an impact on all biological functions and analyzing how body size impacts functional traits such as locomotion is critical. Body size does not only vary across species but also during ontogeny. Indeed, juvenile animals are often at a competitive disadvantage due to their smaller absolute size. Consequently, understanding size- and age-related changes in the locomotor system is critical for our understanding of adult phenotypes. Here, we address this question by exploring growth of the hind limb muscles in two species of closely related baboons that differ in their ecology, the olive baboon, Papio Anubis, the Guinea baboon, and Papio papio. To do so, we dissected 40 P. anubis and 10 P. papio and measured the mass and physiological cross-sectional area (PCSA) of the hind limb muscles. Our results showed no sexual differences in size- or age-related growth patterns, but did show differences between species. Whereas the scaling of muscle mass and PCSA was largely isometric in P. anubis, allometric scaling was more common in P. papio. Despite these differences between species, the knee extensors and external rotators at the knee scaled with positive allometry in both species highlighting their important role during adult locomotion. Although life-history data for P. papio are scarce, we suggest that differences between species may be associated with differences in adult body size and age of locomotor independence between species.

Pre-Copulatory Sexual Selection Predicts Sexual Size Dimorphism: A Meta-Analysis of Comparative Studies.

Size differences between males and females are common across the tree of life (termed sexual size dimorphism; SSD), and have fundamental implications for ecology, life history and behaviour of both sexes. Conventionally, SSD is thought to evolve in response to sex-specific sexual selection but more recent work suggests that ecological processes can also promote sex-differences in size. Here, we provide a global test for the role of sexual selection in the evolution of sexual size dimorphism using data from 77 comparative studies spanning the major classes of the animal kingdom. We show that intense sexual selection typically correlates with male-biased SSD across species. Importantly, pre-copulatory but not post-copulatory sexual selection predicts SSD, suggesting a pervasive role of premating male-male competition and female choice to drive sex differences in body size. Collectively, our findings suggest that pre-copulatory sexual selection plays a major role in the evolution of male-biased SSD.

Morphological and functional analyses for investigation of sexually selected legs in the frog legged beetle Sagra femorata (Coleoptera: Chrysomelidae)

Mate choice and male–male combat over successful mating often cause disproportionate exaggeration of male trait relative to body size. However, the exaggeration is often not the only trait involved with male–male combat and mate choice: suites of co-expressed traits may function together as a coordinated unit. When this occurs, dimorphism may be expected for these additional, non-exaggerated, structures. S. femorata males have disproportionately large hind-legs used in male–male combat over females. During the fights, fore- and mid-legs are used to keep males in positions where advantageous for leverage. Because use of the exaggerated hind-legs is coordinated with the other legs, they will coevolve as a functional unit. Here, we show that 1) S. femorata has sexual size differences in all three legs; 2) males show positive allometry in the relative sizes of all three legs; and 3) microstructures of tarsi on the fore- and mid-legs are also sexually dimorphic. Despite these differences in the tarsal microstructure, 4) adhesion forces of the tarsi had no sexual difference in flat surface. The microstructure would be specialized on attaching elytra surface. These results suggest that the three pairs of legs function together during fighting behavior, with hind-legs employed primarily for fighting, and the fore- and mid-legs functioning to grip females, keeping males positioned on the back of the female during combat.

Are red-crested cardinals Paroaria coronata (Aves: Thraupidae) truly monomorphic?: evidence discloses sexual dichromatism and size differences since the nestling stage

Are red-crested cardinals Paroaria coronata (Aves: Thraupidae) truly monomorphic?: evidence discloses sexual dichromatism and size differences since the nestling stage

Sexual differences in size and chemical composition of antennae of American cockroach, Periplaneta americana (Dictyoptera, Blattodea)

Insect make use of their antennae for sensory purposes, in search for food, mating partners and any other necessary communications. In this study, sexual differences in the measurements and ionic concentration of the adult American cockroach, Periplaneta

Morphometrics of Houbara Bustards Chlamydotis spp: Sexual Size Dimorphism, Seasonal Changes and Differences between Species

Morphometrics of Houbara Bustards Chlamydotis spp: Sexual Size Dimorphism, Seasonal Changes and Differences between Species

Example of Sexual Dimorphism and Structural Defects in Some Aquatic Insects (Coleoptera)

Freshwater is a very important part of the ecosystem. Aquatic insects are at the center of importance of fresh waters due to their remarkable number and diversity.. The purpose of this study was to compare the morphological differences in male and female individuals with the arithmetic mean of some body measurements and to give a summary of rare unexpected structural disorders. On observing sexual dimorphism, Helophorus aquaticus Linnaeus, 1758 (Coleoptera) specimens were selected from the samples collected from Erzurum Wetlands (Turkey) between April and October (2021), as it has a large body and their number in the collection was sufficient. Measurements were performed under a stereo microscope. In this context, some differences in measurements were evaluated by considering sexual dimorphism, some structural disorders and gender-developmental stages in our study. Along with some ecological data, like sexual difference of approximately 100 samples, measurement differences were identified with body length 0.1-0.4 mm, body width 0.1-0.3 mm and leg length 0.1-0.3 mm. There are differences in measurements between the two groups, and in some species belonging to some families of the other Coleptera order, individuals with structural disorders have been identified.. It is believed that the developmental stages and sexual dimorphism size differences are important data for future ecological and evolutionary studies.

CircRNA Identification and CircRNA–miRNA–mRNA Network in Cynoglossus semilaevis Sexual Size Dimorphism

Simple SummaryChinese tongue sole (Cynoglossus semilaevis) typically displays female-biased sexual size dimorphism (SSD), but its epigenetic regulatory mechanisms are poorly understood, especially the role of circRNAs. To explore the function of circRNAs in Chinese tongue sole SSD, we firstly identified differentially expressed circular RNAs (DE circRNAs) in female, male, and pseudo-male C. semilaevis. Secondly, the ceRNA network containing DE circRNAs, miRNAs, and mRNAs in the three genders was constructed. Among the ceRNA network, several circRNAs such as novel_circ_004374 and novel_circ_014597 may regulate hipk2 expression by sponging miR-130-x. It is also worth exploring whether or how novel_circ_008696 regulates setd2 by binding to novel-m0387-3p. The present study provided the cirRNA and its ceRNA network that potentially regulate C. semileavis female-biased SSD for the first time. Sexual size dimorphism (SSD), which is the sexual differences in body size, has been widely reported in various species including fishes. For Chinese tongue sole (Cynoglossus semilaevis), a flatfish exhibiting typically female-biased SSD, little is known for its epigenetic regulation mechanism, especially the role of circRNAs. Here, we identified the differently expressed abundances of circRNAs in females, males, and pseudo-males to explore the potential functions of circRNAs in Chinese tongue sole SSD. In total, 14,745 novel circRNAs were screened, among which 1461 DE circRNAs were identified from the brain, gonad, liver, and muscle in female, male, and pseudo-male individuals. The ceRNA network was subsequently constructed, including 10 circRNAs, 26 mRNAs, and 11 miRNAs. These DE mRNAs were mainly related to the mRNA surveillance pathway, metabolic pathways, and cellular senescence. Importantly, the ceRNA network has revealed that several circRNAs such as novel_circ_004374 and novel_circ_014597 may regulate homeodomain interacting protein kinase 2 (hipk2) expression by sponging miR-130-x. It is also worth exploring whether or how novel_circ_008696 regulates SET Domain Containing 2, histone lysine methyltransferase (setd2), which in turn affects the epigenetic patterns of different sexual individuals. The present study not only enriches the knowledge on the potential roles of circRNA in the physiological process, but also provides new clues for the explanation of fish SSD. In future studies, the precise function and involvement of circRNAs in female-biased SSD will require more efforts.

A Geometric Morphometric Study on Sexual Dimorphism in Viscerocranium.

Simple SummarySex estimation is a crucial step in the identification of unknown bone remains. The accuracy of sex estimation methods depends on the level of sexual dimorphism manifested by the human bones. Therefore, the evaluation of sex differences of particular bones of the skeleton is an important preceding stage. We have used geometric morphometric techniques to investigate the sexual dimorphism in the size and shape of the facial part of the skull and its subregions. Our results show that the facial skeleton in males and females differs more in size than in shape, so its overall size is a more useful sex indicator than its shape. The same result is observed for all facial subregions studied here. However, the best discrimination between the male and female skulls is achieved when both size and shape are considered together.The level of sexual dimorphism manifested by human bones is an important factor for development of effective sex estimation methods. The aim of the study was to investigate the sexual dimorphism in the size and shape of the viscerocranium using geometric morphometric techniques. It also aimed to explore the sex differences in distinct viscerocranial regions and to establish the most dimorphic region with regard to size and shape. Computed tomography images of 156 males and 184 females were used in the study. Three-dimensional coordinates of 31 landmarks were acquired. Five landmark configurations were constructed from the viscerocranium and its orbital, nasal, maxillary, and zygomatic region. Generalized Procrustes superimposition, principal component analysis, and discriminant analysis were applied to each configuration. The significance of the sex differences in size and shape was assessed and significant differences were found in all configurations. The highest accuracy was obtained from both shape and size of the whole viscerocranium. Based on size only, the highest accuracy was achieved by the nasal region. The accuracy based on shape was generally low for all configurations, but the highest result was attained by the orbital region. Hence, size is a better sex discriminator than shape.

Sexual dimorphism in structures, size and shape of the cyprinid Nilgiri melon barb, Haludaria fasciata

Abstract The morphological differences between the sexes of a species is relevant to its captive breeding, ethology, and eco-biology and are studied extensively in fishes. In this paper, we analyzed the sexual dimorphism of the cyprinid Nilgiri melon barb, Haludaria fasciata (Jerdon), in their external structures, size, and shape. Physical examination, microscopical analysis, and morphometric and geometrical analyses of both sexes of the fish were conducted. The presence of tubercle pits and protuberant tubercles on the snout and orbital region were observed in males, while these were absent in females. Smaller-sized tubercles were arranged like a serration on the pectoral fin of males. Body size analysis indicated significant sexual size differences (P < 0.05) in body depth, fork length, eye diameter, pectoral fin length, and caudal fin length. Shape analysis indicated that the coordinate lengths L8 and L1 were the two that were significantly different (P < 0.05) between the sexes. In global redundancy trace analysis of vertices, the males in the population had more substantial variations in their shapes than did females. The paper discusses the possible functions linked with the dimorphic traits identified in H. fasciata.

Marine turtles are only minimally sexually size dimorphic, a pattern that is distinct from most nonmarine aquatic turtles.

Turtles have been prominent subjects of sexual size dimorphism (SSD) analyses due to their compact taxonomy, mating systems, and habitat diversity. In prior studies, marine turtles were grouped with fully aquatic non‐marine turtles (NMATs). This is interesting because it is well‐established that the marine environment imposes a distinct selective milieu on body form of vagile vertebrates, driven by convergent adaptations for energy‐efficient propulsion and drag reduction. We generated a comprehensive database of adult marine turtle body sizes (38,569 observations across all species), which we then used to evaluate the magnitude of SSD in marine turtles and how it compares to SSD in NMAT. We find that marine turtles are only minimally sexually size dimorphic, whereas NMAT typically exhibit female‐biased SSD. We argue that the reason for this difference is the sustained long‐distance swimming that characterizes marine turtle ecology, which entails significant energetic costs incurred by both sexes. Hence, the ability of either sex to allocate proportionately more to growth than the other is likely constrained, meaning that sexual differences in growth and resultant body size are not possible. Consequently, grouping marine turtles with NMAT dilutes the statistical signature of different kinds of selection on SSD and should be avoided in future studies.

Morphological characterization and the significance of sexual differences in size among Lipochromic Mosaic Canary bird raised in the Wilaya of Tlemcen Northwest of Algeria

The lipochromic mosaic canary is a cage bird breed present with different coat colors, red, and yellow, this breed presents a significant sexual dichromatism. Dichromatism in lipochromic mosaic canaries is explained by differential carotenoid degradation in the integument, rather than sex-specific variation in physiological functions such as pigment uptake or transport. Males have an intense color compared to females and especially at the shoulders and head. We studied sexual size dimorphism (SSD) because this study aimed to investigate whether gender has an impact on thirteen body measurements which are (Head Length, Head Width, Distance Between the Eyes, Beak Length, Beak Width, Chest Circumference, Body Length, Body Width, Wing Length, Sternum Length, Upper Tarsus Length, Lower Tarsus Length, and Tail Length) in 40 native lipochromic mosaic canaries (19 males and 21 females) raised in the Wilaya of Tlemcen Northwest of Algeria. The results showed that there were differences between genders for three characters that are CC (Chest Circumference), BL (Body Length), and WL (Wing Length). Males had more developed measurable traits than females.

Metabarcoding prey DNA from fecal samples of adult dragonflies shows no predicted sex differences, and substantial inter-individual variation, in diets.

Sexes often differ in foraging and diet, which is associated with sex differences in size, trophic morphology, use of habitats, and/or life history tactics. Herein, strikingly similar diets were found for adult sexes of a dragonfly (Leucorrhinia intacta), based on comparing 141 dietary taxa identified from the metabarcoding of mitochondrial DNA archived in feces. Arthropods in > 5% of samples included five species of dipterans, two hemipterans, two spider species and one parasitic mite. The mite was not traditional prey as its presence was likely due to DNA contamination of samples arising through parasitism or possibly via accidental consumption during grooming, and therefore the mite was excluded from diet characterizations. Common prey species were found with statistically indistinguishable frequencies in male and female diets, with one exception of an aphid more often found in male diets, although this pattern was not robust to corrections for multiple statistical tests. While rare prey species were often found in diets of only one sex, instances of this were more frequent in the more oft-sampled females, suggesting sampling artefact. Sexes did not differ in the mean prey species richness in their diets. Overall, sexes showed statistically indistinguishable diets both on a prey species-by-species basis and in terms of multivariate characterizations of diet composition, derived from presence-absence data of prey species analyzed via PERMANOVA and accumulation curves. Males and females may have similar diets by being both opportunistic and generalist predators of arthropods, using the same foraging habitats and having similar sizes and flight agilities. Notably, similarities in diet between sexes occur alongside large interindividual differences in diet, within sexes. Researchers intending on explaining adaptive sex differences in diet should consider characteristics of species whose sexes show similar diets.

Sexual Dimorphism and Morphological Modularity in Acanthoscelides obtectus (Say, 1831) (Coleoptera: Chrysomelidae): A Geometric Morphometric Approach.

Simple SummaryThe seed beetle Acanthoscelides obtectus used in this study is a worldwide pest species that inhabits storage facilities and fields of beans. Knowing that sexual dimorphism is very common among insects, we investigated the level of morphological differences between the sexes. Such an approach allowed us to look into the modular organization of this organism. As expected, the females were larger than the males. The observed two modular organization (thorax and abdomen) was sex specific, indicating that reproductive function has the central role in forming the patterns of modularity. It seems that natural selection is driving force for females, while males are influenced more by sexual selection.Sexual dimorphism and specific patterns of development contribute in a great manner to the direction and degree of the sexual differences in body size and shape in many insects. Using a landmark-based geometric morpohometrics approach, we investigated sex-specific morphological size and shape variation in the seed beetle, Acanthoscelides obtectus. We also tested the functional hypothesis of the two morphological modules—thorax and abdomen in both sexes. Female-biased sexual dimorphism in size was shown, while differences in shape were reflected in the wider thorax and abdomen and shorter abdomen in females in comparison to males. The functional hypothesis of a two-module body was confirmed only in females before correction for size, and in both sexes after the allometry correction. Our results indicate that reproductive function has the central role in forming the patterns of modularity. We hypothesize that high morphological integration of the abdomen in females results from intense stabilizing selection, while the more relaxed integration in males is driven by the higher intensity of sexual selection.

Manipulating parental condition affects brood sex ratio, immunocompetence, and early chick mortality in two gull species differing in sexual size dimorphism

AbstractSex allocation theory predicts that parents should adjust their brood sex ratio to maximize fitness returns in relation to parental investment. Adaptive adjustment of sex ratio may be driven by differential costs of rearing sons and daughters or differential benefits of investing limited resources into offspring of different sex. In both cases, possible sex ratio bias should depend on parental condition. For sexually dimorphic birds with males larger than females, sons may be less likely to fledge since they are more vulnerable to food shortages or because they have impaired immunocompetence due to higher testosterone levels. Poor condition females should thus overproduce daughters to minimize possible reproductive failure. We manipulated the number of eggs laid and the amount of food available to laying females to induce differences in the condition in 2 gull species differing in sexual size dimorphism. In the Black-headed Gull (Chroicocephalus ridibundus), sexual size differences are marginal; but in the Mew Gull (Larus canus), males are 11% larger. In both species, females forced to lay an additional egg (presumed in worse condition) overproduced daughters, whereas females receiving supplemental food before laying (presumed improved condition) overproduced sons. This sex ratio skew was larger in Mew Gull, a species with larger size dimorphism. Chick immunocompetence at hatching was unrelated to sex, being higher in broods of fed mothers and lower for chicks hatched from last-laid eggs. Chick survival between hatching and day 5 post-hatch was positively related to their immunocompetence, but chicks from last-laid eggs and males of Mew Gull, the more dimorphic species, survived less well. Results indicate that costs of raising larger sex offspring coupled with parental condition shape brood sex ratio in populations studied. Adaptive brood sex ratio adjustment occurs mostly before egg laying and includes differential sex allocation in eggs depending on the probability of producing a fledged chick.

Morphometric analysis of the occipital bone in an adult South African cadaveric sample.

Forensic sex estimation is a key component in attempts to identify human remains. The skull is often used for this purpose, but is often damaged or recovered in fragments. Studies of individual cranial bones are hampered by subjectivity in visual assessment and difficulties in the ability to capture complex shape variations, as well as accounting for population-specificity in the expression of sexual dimorphism. The present study employed geometric morphometric analysis to assess morphological variation of the occipital bones of 792 adult South African individuals. Though sexual differences in size were detected, shape dimorphism was not detected until ancestry was simultaneously accounted for. Female occipital bones were less robust but more sloped than those of males. Detected variation between ancestry groups was sufficient to produce approximately 80% classification accuracies for Black and White groups, and 74% for the highly heterogeneous Coloured group. When variation was assessed according to sex and ancestry simultaneously, groups could be distinguished with 74.8% accuracy. Shape variation showed no significant age or secular trend changes, though some weak positive allometric influence was detected in the variation between sexes and between the Coloured group and the other two ancestry groups. This study demonstrated that even isolated bones such as the occipital could be used for sex and ancestry estimation, though population differences must be considered. The geometric morphometric analysis was found to allow objective and sufficiently sensitive detection of variation in the complex occipital shape to allow for accurate distinction of even highly heterogeneous and closely related groups, even when using a limited number of cranial landmarks. Thus, similar analyses of the occipital may be employed in forensic cases where the cranium has been damaged or only the occipital bone is recovered and available for analysis.

Chronological and regional variation in developmental stress and behavior of Early and Late Neolithic Cis-Baikal hunter-gatherer juveniles: Insights from diaphyseal cross-sectional geometry

This study explores growth (increase in size) and development (change in structure and function) in Middle Holocene Cis-Baikal hunter-gatherer populations to evaluate chronological and regional variation in developmental health and juvenile behavior using post-cranial Cross-Sectional Geometry (CSG). It also evaluates whether sexual differences in size and habitual behavior were evident by the end of adolescence. Age and body size standardized femur, tibia, and humerus midshaft CSG are used to test for differences between Early Neolithic (EN) and Late Neolithic (LN) juveniles from different micro-regions. Regression of these measures on radiocarbon date tests for differences within archaeological periods.EN individuals younger than 16 years, particularly those from the Angara River Valley, exhibit lower measures of cross-sectional size/ rigidity than LN juveniles. EN individuals older than 6 years, especially those from the Southwest Baikal had less circular lower limbs and higher humerus percent cortical area than LN individuals. Age standardized cross sectional size/ rigidity decline throughout both the EN and the LN, suggesting decrease in body size during both archaeological periods, whereas changes in femur shape are consistent with increases in juvenile mobility throughout the EN. By the end of adolescence, sexual dimorphism is emerging but not fully established in lower and upper limb robusticity and shape.The lower cross-sectional area and bending rigidity support higher levels of developmental stress in the EN compared to the LN period, whereas less circular lower limb indices suggest higher terrestrial mobility in the EN. These differences may reflect may a higher risk of resource scarcity in the EN, which resulted in higher mobility and greater involvement of juveniles in harvesting aquatic resources. Declines in body size within both archaeological periods emphasize the cyclical nature of developmental stress, perhaps due to declines in resource abundance. The presence of incipient sexual dimorphism by the end of adolescence is consistent with individuals beginning to assume adult roles.

Sexual dimorphism in Scutiger boulengeri, an endemic toad from the Tibetan Plateau

Abstract The evolution of sexual dimorphism has long fascinated evolutionary biologists and theory suggests that variation in sexual dimorphism is a consequence of selective forces acting differently on morphological traits in males versus females. Here, we analyzed sexual differences in size and shape of the Boulenger’s lazy toad, Scutiger boulengeri, based on the intersex variation pattern of sixteen morphometric traits including body size. The results suggested that sexual dimorphism was apparent in body size and some body shapes (e.g., head length and width, internasal space, interorbital space, diameter of lower arm and tibia width) of this toad. The bigger body size in females may be relevant to fecundity selection, a larger head in males as well as a broader internasal and interorbital space may be subject to male-male competition in combination with ecological selection, and both robust forelimbs and hindlimbs in males may be related to mating and competitive behaviors. These results are discussed with respect to the above selection procedures and possible sex differences in life history traits.

Sexual Dimorphism of Size Ontogeny and Life History

Background: Ecological and physiological factors and social and economic constraints affect sex-specific body size. Here, we used the male/female (M/F) height ratio as an indicator of the combined effect of genetic and sex characteristics. We hypothesized that (1) sexual dimorphism in body size will be established during infancy and adolescence when growth velocity is maximal, (2) living standards and health are important factors which can affect sexual dimorphism in body size, (3) variations in sexual dimorphism in body size are due to the differential response of boys and girls to environmental cues, and (4) sexual dimorphism in body size will be more pronounced in those populations whose average height and weight are the greatest.Methods: To study the ontogeny of sexual dimorphism from birth until the age of 18 years, we used the 2000 CDC growth data. Data on height by country, life expectancy, and gross domestic product (GDP) per capita based on purchasing power parity were extracted from the national accounts data of NCD Risk Factor Collaboration, the World Bank, Eurostat: Demographic Statistics, Secretariat of the Pacific Community: Statistics and Demography Program, and the US Census Bureau.Results: We found that sexual dimorphism in body size starts at age 1 month, peaks at age 3 months, and diminishes by age 24 months. During childhood, there is no sexual difference in body size, and it is gradually established when the boys enter puberty. The M/F height ratio correlates positively with the average male and female height and weight by country.Conclusion: Sexual dimorphism in body size occurs when (a) the growth velocity is maximal during infancy and adolescence, (b) living standards are high, and health correlate positively with male/female height ratio. Anthropological studies and our results emphasize mostly the female resiliency hypothesis: shorter male heights in times of environmental stress lead to smaller sexual dimorphism in body size.

Little if any role of male gonadal androgens in ontogeny of sexual dimorphism in body size and cranial casque in chameleons

Proximate control of the development of sexual dimorphism is still hotly debated in reptiles. In some squamates, many male-typical exaggerated traits including body size were assumed to be controlled by masculinization by male gonadal androgens. We performed a manipulative experiment to test the importance of this mechanism in the development of pronounced sexual differences in body size and size of head casque in the chameleon Chamaeleo calyptratus. Castrated males attained male-typical body size highly deviating from the body size of control females. Ontogenetic allometries of casque size on head length revealed that sexes depart considerably in casque growth later in the ontogeny; however, castrated males still follow male-typical casque growth. Paradoxically, exogenous testosterone led in females to slight increase of casque size, which might reflect interference with the feminizing effects of female gonadal hormones. The results in males strongly suggest that masculinization by male gonadal androgens during growth is not required for the development of sexual dimorphism in body size and casque size in the chameleon. The ontogeny of sexually dimorphic body size and exaggerated traits in at least some squamates is likely controlled by other proximate mechanism, possibly by feminization by ovarian hormones.