scholarly journals Sexual dimorphism in size and shape of the head in the sea snake Emydocephalus annulatus (Hydrophiinae, Elapidae)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Richard Shine ◽  
Claire Goiran
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Body Length ◽  
Field Studies ◽  
Head Size ◽  
Head Shape ◽  
Fish Eggs ◽  
Sea Snake ◽  
Size And Shape ◽  
Prey Items

AbstractIn snakes, divergence in head size between the sexes has been interpreted as an adaptation to intersexual niche divergence. By overcoming gape-limitation, a larger head enables snakes of one sex to ingest larger prey items. Under this hypothesis, we do not expect a species that consumes only tiny prey items to exhibit sex differences in relative head size, or to show empirical links between relative head size and fitness-relevant traits such as growth and fecundity. Our field studies on the sea snake Emydocephalus annulatus falsify these predictions. Although these snakes feed exclusively on fish eggs, the heads of female snakes are longer and wider than those of males at the same body length. Individuals with wider heads grew more rapidly, reproduced more often, and produced larger litters. Thus, head shape can affect fitness and can diverge between the sexes even without gape-limitation. Head size and shape may facilitate other aspects of feeding (such as the ability to scrape eggs off coral) and locomotion (hydrodynamics); and a smaller head may advantage the sex that is more mobile, and that obtains its prey in narrow crevices rather than in more exposed situations (i.e., males).

Factors driving sexual dimorphism and colour variability in the Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in central Argentina

2020 ◽  
Vol 98 (6) ◽  
pp. 377-389
Author(s):  
S. Naretto ◽  
M. Chiaraviglio
Keyword(s):  
Sex Differences ◽  
Spatial Distribution ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Endemic Species ◽  
Morphological Changes ◽  
Head Size ◽  
Head Width ◽  
Temporal And Spatial Distribution ◽  
Central Argentina

The intensity of mating competition varies according to the temporal and spatial distribution of individuals. Measuring sexual dimorphism over time and interpreting the association between individuals is therefore important if we aim to understand how sexual traits are influenced. We examined sex differences in the Achala Copper Lizard (Pristidactylus achalensis (Gallardo, 1964)), an endemic species from the highest part of mountains of central Argentina. Over 4 years, we explored sex-specific variation in body size, head size, interlimb length, and body colouration. Furthermore, we evaluated how these traits varied temporally, and we also explored whether the spatial distribution of individuals is explained by variation in these traits. We found that P. achalensis is a species with sexual dimorphism in multiple characters, including body size, head size, and colouration. Interestingly, some traits related to mating, such as head width, show a temporal variability in both sexes, whereas other traits, such as colouration, varies seasonally only in males. Our results underline the intriguing possibility of seasonal morphological changes related to mating, and more broadly that sex differences are influenced by sexual selection pressures mediated by temporal variation in mate competition.

scholarly journals Post-metamorphic ontogenetic changes in head size and shape of the pool frog (Pelophylax lessonae, Ranidae)

2018 ◽  
Vol 70 (2) ◽  
pp. 307-312 ◽  
Author(s):  
Tanja Vukov ◽  
Milica Kurucki ◽  
Marko Andjelkovic ◽  
Natasa Tomasevic-Kolarov
Keyword(s):  
Posterior Part ◽  
Maximum Size ◽  
Head Size ◽  
Head Width ◽  
Ontogenetic Changes ◽  
Head Shape ◽  
Positive Correlation ◽  
Size And Shape ◽  
Ecological Relevance ◽  
Metamorphic Development

Post-metamorphic ontogenetic variations of head size and shape were investigated in the pool frog (Pelophylax lessonae, Ranidae). We showed that allometry is an important aspect of the post-metamorphic ontogeny of the pool frog as most of the differences between the head shape of subadults and adults were size-related adjustments. The largest changes affected by size variations included the posterior part of the head and the snout and eye region. In comparison to subadults, adults have wider heads, shorter snouts and relatively smaller eyes. Analyses of the relationships between head size and shape and the maximum size of the prey indicated the absence of correlations in adults. A positive correlation was found in subadults, but only between head width and the maximum size of the prey. Further studies will allow us to draw more generalized conclusions about the ecological relevance of the variations in head size and shape during post-metamorphic development of the pool frog.

scholarly journals Sexual dimorphism and skull size and shape in the highly specialized snake species, Aipysurus eydouxii (Elapidae: Hydrophiinae)

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11311
Author(s):  
Bartosz Borczyk ◽  
Łukasz Paśko ◽  
Jan Kusznierz ◽  
Stanisław Bury
Keyword(s):  
Sexual Dimorphism ◽  
Body Length ◽  
Prey Size ◽  
Feeding Habits ◽  
Skull Morphology ◽  
Data Set ◽  
Skull Shape ◽  
Size And Shape ◽  
Mandibular Fossa ◽  
Males And Females

Background Snakes exhibit sexual dimorphism in both head size and shape. Such differences are often attributed to different reproductive roles and feeding habits. We aim to investigate how sexual dimorphism is displayed in the highly specialised fish-egg-eating snake, Aipysurus eydouxii, by analysing two complementary features: body size and skull morphology. Methods We used data on body length, weight, and skull shape from 27 measurements of 116 males and females of A. eydouxii. We investigated both sexual dimorphism and allometric (multivariate and bi-variate) properties of skull growth in the analysed data set. Results We found that although there was female-biased sexual size dimorphism in body length, females were not heavier than males, contrary to what is commonly observed pattern among snakes. Moreover, females tend to possess relatively smaller heads than males. However, we only found very subtle differences in skull shape reflected in nasal width, mandibular fossa, quadrate crest and quadrate length. Discussion We suggest that the feeding specialisation in A. eydouxii does not allow for an increase in body thickness and the size of the head above a certain threshold. Our results may be interpreted as support for prey-size divergence as a factor driving skull dimorphism since such species in which the sexes do not differ in prey size also shows very subtle or no differences in skull morphology.

scholarly journals Differences in head size and shape during the growth of Deutero Malay children

2019 ◽  
Vol 31 (1) ◽  
pp. 53
Author(s):  
Ameta Primasari ◽  
Veronica Angelia ◽  
Dimas Agara
Keyword(s):  
Age Groups ◽  
Human Head ◽  
Head Size ◽  
Age Group ◽  
Cephalic Index ◽  
Head Shape ◽  
Cross Sectional ◽  
Size And Shape ◽  
Significant Difference ◽  
Head Height

Introduction: The growth periods of 0-18 years old can be studied with anthropometry by identifying the head size and shape of the human head. Study on vertical, transverse, and horizontal cephalic indexes can understand differences and growth between sexes and age groups. This study was aimed to analyse the averages and differences in the head size and shape of Deutero Malay children in different age groups. Methods: This research was a descriptive analytic study with cross-sectional design. The sample of 192 Deutero Malay children consisted of boys and girls with an age range of 7-18 years old. Measurement of head height, length, and width was performed to calculate the differences of vertical, transverse, and horizontal cephalic index values by sex and age group, and the classification of the head shape based on the cephalic index values. Results: There was a difference of vertical, transverse, and horizontal by age group, with p = 0.000 (p < 0.05). The average of vertical, transverse, and horizontal cephalic index values was significantly higher in each age group. The average horizontal cephalic index was significantly higher in boys and girls. There was no significant difference in the head shape by the vertical and horizontal cephalic index in all age groups. The highest vertical cephalic index found was chamaecephalic (68%). The highest transverse cephalic index was tapeiocephalic (99%). The highest horizontal cephalic index was hyperbrachycephalic (80%). Conclusion: There is similar head shape of Deutero Malay children, although there may be increasing head size along with age. Keywords: Deutero Malay, head shape, cephalic index, transverse cephalic index, horizontal cephalic index, vertical cephalic index

scholarly journals Regulatory Role of Sex Hormones in Cardiovascular Calcification

2021 ◽  
Vol 22 (9) ◽  
pp. 4620
Author(s):  
Holly J. Woodward ◽  
Dongxing Zhu ◽  
Patrick W. F. Hadoke ◽  
Victoria E. MacRae
Keyword(s):  
Cardiovascular Disease ◽  
Sex Differences ◽  
Sexual Dimorphism ◽  
Aortic Stenosis ◽  
Sex Hormones ◽  
Sex Hormone ◽  
Increased Risk ◽  
Male Sex ◽  
Primary Male

Sex differences in cardiovascular disease (CVD), including aortic stenosis, atherosclerosis and cardiovascular calcification, are well documented. High levels of testosterone, the primary male sex hormone, are associated with increased risk of cardiovascular calcification, whilst estrogen, the primary female sex hormone, is considered cardioprotective. Current understanding of sexual dimorphism in cardiovascular calcification is still very limited. This review assesses the evidence that the actions of sex hormones influence the development of cardiovascular calcification. We address the current question of whether sex hormones could play a role in the sexual dimorphism seen in cardiovascular calcification, by discussing potential mechanisms of actions of sex hormones and evidence in pre-clinical research. More advanced investigations and understanding of sex hormones in calcification could provide a better translational outcome for those suffering with cardiovascular calcification.

296 Sex differences in sleep and wakefulness of police officers working shifts: evidence from a field study

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A118-A118
Author(s):  
Gabriela Caetano ◽  
Laura Kervezee ◽  
Fernando Gonzales-Aste ◽  
Philippe Boudreau ◽  
Diane Boivin
Keyword(s):  
Sex Differences ◽  
Circadian Rhythms ◽  
Shift Work ◽  
Police Officers ◽  
Field Studies ◽  
Time Of Day ◽  
Cycle Phase ◽  
Shift Workers ◽  
Work Related ◽  
Time Awake

Abstract Introduction National reports of work-related injuries found the excess risk of work injury attributed to shift work to be significantly higher among women. The Working Time Society (WTS) concluded that male sex is one of the few factors that is “consistently associated with perceived or actual shift work tolerance”. However, it is unclear if physiological parameters are involved. Laboratory-controlled studies report sex differences in circadian rhythms (body temperature, melatonin). In sleep deprivation protocols, alertness and cognitive performances were affected by sex, menstrual cycle phase and hormonal contraceptives [HC] use. Nevertheless, field studies that compare male and female shift workers are scarce. Methods An observational study including 76 police officers working on patrol: 56 males and 20 females (11 using [HC], 6 not using [non-HC] and 3 with unknown use of hormonal contraception) aged 32.0 ± 5.3 years. Participants were followed throughout a month-long work cycle (1,457 morning, evening, night, or other shifts, plus rest days). They filled out time-stamped questionnaires (Samn-Perelli, KSS, Visual Analogue Scales, ~5/day; sleep and work-related information, ~1–2/day), completed 5-min Psychomotor Vigilance Tasks (PVT, ~2/day), and wore an actigraph to collect activity data. Linear mixed-effects models were used to analyze the effects of group, time awake and time-of-day on fatigue, sleepiness, alertness, mood and PVT measures. Results Self-reported measures and psychomotor performance significantly varied with time awake and time-of-day. Fatigue and sleepiness levels were significantly higher among female compared to male police officers, both with time awake and across the 24-h day. These variations were similar between non-HC females and the other groups. Compared to males, HC females were more fatigued and less alert, both with time awake and across the 24-h day, and sleepier with time awake. Having children at home did not explain these differences. Conclusion The results of this study expand our knowledge on the sex differences in the sleep and circadian physiology and demonstrate a critical effect of HC on women fatigue, sleepiness and alertness when working shifts. Sex and hormonal parameters must be considered in occupational medicine as well as in future laboratory and field studies on shift workers and circadian rhythms. Support (if any) IRSST, FRQS.

scholarly journals Sex Differences in the Triad of Acquired Sensorineural Hearing Loss

2021 ◽  
Vol 22 (15) ◽  
pp. 8111
Author(s):  
Kuang-Hsu Lien ◽  
Chao-Hui Yang
Keyword(s):  
Hearing Loss ◽  
Sex Differences ◽  
Sexual Dimorphism ◽  
Sensorineural Hearing Loss ◽  
Hormone Replacement ◽  
Modern Society ◽  
Sensorineural Hearing ◽  
Drug Induced ◽  
Age Related ◽  
Age Related Hearing Loss

The triad of noise-generated, drug-induced, and age-related hearing loss is the major cause of acquired sensorineural hearing loss (ASNHL) in modern society. Although these three forms of hearing loss display similar underlying mechanisms, detailed studies have revealed the presence of sex differences in the auditory system both in human and animal models of ASNHL. However, the sexual dimorphism of hearing varies among noise-induced hearing loss (NIHL), ototoxicity, and age-related hearing loss (ARHL). Importantly, estrogen may play an essential role in modulating the pathophysiological mechanisms in the cochlea and several reports have shown that the effects of hormone replacement therapy on hearing loss are complex. This review will summarize the clinical features of sex differences in ASNHL, compare the animal investigations of cochlear sexual dimorphism in response to the three insults, and address how estrogen affects the auditory organ at molecular levels.

scholarly journals Sexual conflict drives micro- and macroevolution of sexual dimorphism in immunity

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Basabi Bagchi ◽  
Quentin Corbel ◽  
Imroze Khan ◽  
Ellen Payne ◽  
Devshuvam Banerji ◽  
...  
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Mating System ◽  
Sexual Conflict ◽  
Experimental Evolution ◽  
Parasitic Infections ◽  
Pathogen Dynamics ◽  
Trade Offs ◽  
Host Pathogen ◽  
Seed Beetles

Abstract Background Sexual dimorphism in immunity is believed to reflect sex differences in reproductive strategies and trade-offs between competing life history demands. Sexual selection can have major effects on mating rates and sex-specific costs of mating and may thereby influence sex differences in immunity as well as associated host–pathogen dynamics. Yet, experimental evidence linking the mating system to evolved sexual dimorphism in immunity are scarce and the direct effects of mating rate on immunity are not well established. Here, we use transcriptomic analyses, experimental evolution and phylogenetic comparative methods to study the association between the mating system and sexual dimorphism in immunity in seed beetles, where mating causes internal injuries in females. Results We demonstrate that female phenoloxidase (PO) activity, involved in wound healing and defence against parasitic infections, is elevated relative to males. This difference is accompanied by concomitant sex differences in the expression of genes in the prophenoloxidase activating cascade. We document substantial phenotypic plasticity in female PO activity in response to mating and show that experimental evolution under enforced monogamy (resulting in low remating rates and reduced sexual conflict relative to natural polygamy) rapidly decreases female (but not male) PO activity. Moreover, monogamous females had evolved increased tolerance to bacterial infection unrelated to mating, implying that female responses to costly mating may trade off with other aspects of immune defence, an hypothesis which broadly accords with the documented sex differences in gene expression. Finally, female (but not male) PO activity shows correlated evolution with the perceived harmfulness of male genitalia across 12 species of seed beetles, suggesting that sexual conflict has a significant influence on sexual dimorphisms in immunity in this group of insects. Conclusions Our study provides insights into the links between sexual conflict and sexual dimorphism in immunity and suggests that selection pressures moulded by mating interactions can lead to a sex-specific mosaic of immune responses with important implications for host–pathogen dynamics in sexually reproducing organisms.

The nanoanatomical basis of sexual dimorphism in iridescent butterfly colouration

2012 ◽  
Vol 60 (2) ◽  
pp. 101 ◽  
Author(s):  
Thomas E. White ◽  
Joseph Macedonia ◽  
Debra Birch ◽  
Judith Dawes ◽  
Darrell J. Kemp
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Phenotypic Variation ◽  
Functional Variation ◽  
Present Evidence ◽  
Signal Variation ◽  
Common Basis ◽  
Scale Surface ◽  
Colour Signals

Structurally generated colours are at least as commonplace and varied components of animal signals as pigment colours, yet we know far less about the former, both in terms of the patterns and phenotypic variation and of their underlying correlates and causes. Many butterflies exhibit bright and iridescent colour signals that arise from a characteristic ‘ridge-lamellar’ scale surface nanoarchitecture. Although there are multiple axes of functional variation in these traits, few have been investigated. Here we present evidence that sexual dimorphism in the expression of a sexually homologous ridge-lamellar trait (iridescent ultraviolet) is mediated by sex differences in the density of lamellar-bearing scale ridges. This trait – ridge density – has also been causally related to iridescent signal variation in other coliadines (e.g. C. eurytheme), which suggests that it may offer a common basis to both intra- and intersexual differences in ultraviolet wing reflectance among these butterflies.

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