Sexual dimorphism in the antennae of terrestrial isopods: a result of male contests or scramble competition?

2000 ◽  
Vol 78 (11) ◽  
pp. 1987-1993 ◽  
Author(s):  
F Lefebvre ◽  
M Limousin ◽  
Y Caubet
Keyword(s):  
Sexual Dimorphism ◽  
Negative Correlation ◽  
Morphological Analysis ◽  
Scramble Competition ◽  
Behavioral Analysis ◽  
Sexually Dimorphic ◽  
Selection Pressures ◽  
Terrestrial Isopods ◽  
Male Contests

In Oniscidea (terrestrial crustaceans), males are known to have longer antennae than females. This sexual dimorphism may result from a variety of selection pressures. However, some species are well known for their highly aggressive males, which use their antennae as weapons. We tested the hypothesis that longer antennae in males have been selected for by means of antennal contests. Morphological analysis of the antennae and behavioral analysis of male dyads were performed in parallel on 7 species. We demonstrate significant sexual dimorphism of the antennae in 6 of the 7 species, and various forms of male aggressiveness depending on the species. Our hypothesis was rejected because we found a negative correlation between the use of the antennae in contests and the magnitude of sexual dimorphism. Furthermore, some species are sexually dimorphic but the males never compete using their antennae. We propose and argue that scramble competition to be the first to find receptive females could explain why males have longer chemoreceptive antennae.

scholarly journals X chromosome escapee genes are involved in ischemic sexual dimorphism through epigenetic modification of inflammatory signals

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Shaohua Qi ◽  
Abdullah Al Mamun ◽  
Conelius Ngwa ◽  
Sharmeen Romana ◽  
Rodney Ritzel ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
X Chromosome ◽  
Epigenetic Modification ◽  
Artery Occlusion ◽  
Sexually Dimorphic ◽  
Mrna Levels ◽  
Young Females ◽  
Human Stroke ◽  
Histone H3k4 ◽  
Cerebral Artery Occlusion

Abstract Background Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity. Methods To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production. Results Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines. Conclusions The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.

The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia

2021 ◽  
Vol 13 (590) ◽  
pp. eabd6434
Author(s):  
Patrick Sweeney ◽  
Michelle N. Bedenbaugh ◽  
Jose Maldonado ◽  
Pauline Pan ◽  
Katelyn Fowler ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Critical Role ◽  
Brain Regions ◽  
Sexually Dimorphic ◽  
Male And Female ◽  
Female Mice ◽  
Bidirectional Regulation ◽  
Fear And Anxiety ◽  
Agouti Related Protein

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

scholarly journals Sexual dimorphism in a top predator ( Notophthalmus viridescens ) drives aquatic prey community assembly

2018 ◽  
Vol 285 (1890) ◽  
pp. 20181717 ◽  
Author(s):  
Denon Start ◽  
Stephen De Lisle
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Intraspecific Variation ◽  
Structure And Function ◽  
Sexually Dimorphic ◽  
Ecological Communities ◽  
Top Predator ◽  
Aquatic Mesocosms ◽  
And Function ◽  
The Impact

Intraspecific variation can have important consequences for the structure and function of ecological communities, and serves to link community ecology to evolutionary processes. Differences between the sexes are an overwhelmingly common form of intraspecific variation, but its community-level consequences have never been experimentally investigated. Here, we manipulate the sex ratio of a sexually dimorphic predacious newt in aquatic mesocosms, then track their impact on prey communities. Female and male newts preferentially forage in the benthic and pelagic zones, respectively, causing corresponding reductions in prey abundances in those habitats. Sex ratio differences also explained a large proportion (33%) of differences in the composition of entire pond communities. Ultimately, we demonstrate the impact of known patterns of sexual dimorphism in a predator on its prey, uncovering overlooked links between evolutionary adaptation and the structure of contemporary communities. Given the extreme prevalence of sexual dimorphism, we argue that the independent evolution of the sexes will often have important consequences for ecological communities.

scholarly journals Performance, but not size, of hindleg weaponry is sexually dimorphic in the giant mesquite bug (Thasus neocalifornicus)

2020 ◽  
Author(s):  
Zackary A. Graham ◽  
Nicole Kaiser ◽  
Alexandre V. Palaoro
Keyword(s):  
Sexual Dimorphism ◽  
Muscle Mass ◽  
Sexually Dimorphic ◽  
Aggressive Interaction ◽  
Body Parts ◽  
Single Measure ◽  
Male And Female ◽  
Aggressive Interactions ◽  
Sexual Dimorphisms

ABSTRACTIn many species, males possess specialized weaponry that have evolved to confer a benefit during aggressive interactions. Because male weaponry is typically an exaggerated or extreme version of pre-existing body parts, females often possess reduced or weaponry. Although much research has investigated sexual dimorphism in the sizes of such weapons, other weapon components, such as weapon performance or alternative weapon forms can also explain the evolution of weapon sexual dimorphisms. Here, we investigated the allometry and variation of multiple weapon components of hindleg weaponry in the male and female giant mesquite bugs, Thasus necalifornicus. Despite theory predicating greater allocation in male weaponry, we found that females allocated more into the lengths of their hindlegs compared to males. Despite this allocation, males possess relatively wider hindlegs, which likely increase area of muscle mass. Indeed, the squeezing performance of male hindlegs was much greater than that of female hindlegs. Lastly, we also described the allometry and variation in a male weapon component, prominent tibial spines, which likely are used to damage competitors during aggressive interaction. Overall, our findings highlight the intricacies of weapon sexual dimorphism and demonstrate the importance of measuring multiple weapon components and not a single measure.

scholarly journals Phenotypic Variation in Skull Size and Shape Between Newfoundland and Mainland Populations of North American Black Bears, Ursus americanus

2003 ◽  
Vol 117 (2) ◽  
pp. 236 ◽  
Author(s):  
John A. Virgl ◽  
Shane P. Mahoney ◽  
Kim Mawhinney
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Ursus Americanus ◽  
Population Variation ◽  
Black Bears ◽  
Selection Pressures ◽  
Skull Shape ◽  
Skull Size ◽  
Environmental Selection ◽  
Gape Size

It is well recognized that differences in environmental selection pressures among populations can generate phenotypic divergence in a suite of morphological characteristics and associated life history traits. Previous analysis of mitochondrial DNA and body size have suggested that Black Bears (Ursus americanus) inhabiting the island of Newfoundland represent a different subspecies or ecotype from mainland populations. Assuming that body size covaries positively with skull size, we predicted that skull size would be greater for bears on the island than the mainland, and the distribution of size-related shape components in multivariate space should show a distinct separation between Newfoundland and mainland populations. Measurements of 1080 specimens from Newfoundland, Alberta, New York, and Quebec did not provide unequivocal support for our prediction that skull size in Newfoundland bears would be larger than bears from the mainland populations. After removing ontogenetic effects of skull size, between-population variation in skull shape was greater in females than males, and the analysis significantly separated Newfoundland bears from mainland populations. Explanations for this pattern are numerous, but currently remain hypothetical. Limited covariation between skull size and body size suggests that genetic traits regulating the size of Black Bear skulls are more heritable (i.e., less influenced by environmental selection pressures) than characteristics affecting body size. We hypothesize that if gape size does not limit prey size in solitary terrestrial carnivores, large degrees of among-population variation in body size should be coupled with little covariation in skull size. In general, sexual dimorphism in skull size and shape was marginal for the phenotypic characters measured in our study. We believe that sexual dimorphism in skull size in Black Bears is primarily driven by intrasexual selection in males for increased gape size display, while similarity in skull shape between sexes is associated with the constraints of a temporally-selective, but similar diet.

scholarly journals Auditory brainstem responses in the red-eared slider Trachemys scripta elegans (Testudoformes: Emydidae) reveal sexually dimorphic hearing sensitivity

2019 ◽  
Vol 205 (6) ◽  
pp. 847-854 ◽  
Author(s):  
Tongliang Wang ◽  
Handong Li ◽  
Jianguo Cui ◽  
Xiaofei Zhai ◽  
Haitao Shi ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Tympanic Membrane ◽  
Auditory Brainstem ◽  
Trachemys Scripta ◽  
Auditory Brainstem Responses ◽  
Sexually Dimorphic ◽  
Trachemys Scripta Elegans ◽  
Hearing Sensitivity ◽  
Brainstem Response ◽  
Auditory Systems

Abstract Hearing sensitivity is of general interest from the perspective of understanding the functionality and evolution of vertebrate auditory systems. Sexual dimorphism of auditory systems has been reported in several species of vertebrates, but little is known about this phenomenon in turtles. Some morphological characteristics, such as middle ear and tympanic membrane that influence the hearing sensitivity of animals can result in hearing sexual dimorphism. To examine whether sexual dimorphism in hearing sensitivity occurs in turtles and to compare hearing characteristics with respect to the shape of the tympanic membrane, we measured the hearing sensitivity and tympanum diameter in both sexes of Trachemys scripta elegans. The results showed that, with the exception of 0.9 kHz, auditory brainstem response thresholds were significantly lower in females than in males for frequencies in the 0.2–1.1 kHz range, indicating that the hearing of females shows greater sensitivity. No significant differences were detected in the tympanum diameter of both sexes. These results showed that sexually dimorphic hearing sensitivity has evolved in turtles; however, this difference does not appear to be related to differences in the size of the tympanic membrane. The possible origin and function of the sexual differences in auditory characteristic are discussed.

Remarks on the sexual dimorphism and taxonomy of Fabia Dana, 1851 (Crustacea, Brachyura, Pinnotheridae)

Zootaxa ◽  
2013 ◽  
Vol 3616 (2) ◽  
pp. 190-200 ◽  
Author(s):  
ERNESTO CAMPOS
Keyword(s):  
Sexual Dimorphism ◽  
Sexually Dimorphic ◽  
Female Specimen ◽  
Male Specimen ◽  
Dimorphic Species

A study of the holotype of Pinnotheres hemphilli Rathbun, 1918, revealed it is an early post-hard female, not a male, of Fabia Dana, 1851. The morphology of Pinnotheres emiliai Melo, 1971 (based on a male specimen) and Fabia insularis Melo, 1971 (based on a female specimen) confirm earlier hypothesis that they belong to a sexually dimorphic species that should be known as F. emiliai (Melo, 1971). The redescription of the holotype of Fabia felderi Gore, 1986, supports its generic assignment and its relationship with F. emiliai. The implication of sexual dimorphism and intersexes in the taxon-omy of Fabia is discussed.

scholarly journals Body size, female reproduction and sexual dimorphism in the lizard Ameiva ameiva (Teiidae) in a restinga of southeastern Brazil

2008 ◽  
Vol 25 (2) ◽  
pp. 370-372 ◽  
Author(s):  
Carlos Frederico Duarte Rocha
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Clutch Size ◽  
Reproductive Period ◽  
Southeastern Brazil ◽  
Head Width ◽  
Sexually Dimorphic ◽  
Female Reproduction ◽  
Female Body Size ◽  
Reproductive Body

In this study 57 specimens of the lizard Ameiva ameiva (Linnaeus, 1758) collected in the restinga at Barra de Maricá, in the state of Rio de Janeiro, southeastern Brazil, were analyzed to investigate size relations and reproduction (in females) and sexual dimorphism of this population. We answered the following questions: 1) what is the minimum reproductive body size in females? 2) what is the average clutch size and 3) how is clutch size related to body size? 4) Are body and head sizes sexually dimorphic? Mean clutch size was 6.7 ± 2.1 eggs and was positively correlated with female body size. Sexual dimorphism favoring males was found: adult mean snout-vent length was great in males (124.2 ± 17.8 mm) than females (96.5 ± 23.1 mm SVL), and males were larger with respect to head width and length, and body mass. Thus, despite the marked seasonality at Barra de Maricá, A. ameiva has an extended reproductive period. Also, intrasexual selection may have acted on females to produce larger clutches, and on males, favoring larger males.

scholarly journals Sexual dimorphism of detrusor function demonstrated by urodynamic studies in rhesus macaques

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Natalia P. Biscola ◽  
Kari L. Christe ◽  
Ephron S. Rosenzweig ◽  
Mark H. Tuszynski ◽  
Leif A. Havton
Keyword(s):  
Sexual Dimorphism ◽  
Peak Pressure ◽  
Rhesus Macaques ◽  
Bladder Capacity ◽  
Bladder Pressure ◽  
Sexually Dimorphic ◽  
Pressure Flow ◽  
Pressure Flow Studies ◽  
Detrusor Function ◽  
Male Subjects

Abstract The lower urinary tract (LUT) and micturition reflexes are sexually dimorphic across mammals. Sex as a biological variable is also of critical importance for the development and translation of new medical treatments and therapeutics interventions affecting pelvic organs, including the LUT. However, studies of LUT function with comparisons between the sexes have remained sparse, especially for larger mammals. Detrusor function was investigated by filling cystometry and pressure flow studies in 16 male and 22 female rhesus macaques. By filling cystometry, male subjects exhibited a significantly larger bladder capacity and compliance compared to females. Pressure flow studies showed a significantly higher bladder pressure at voiding onset, peak pressure, and elevation in detrusor-activated bladder pressure from the end of bladder filling to peak pressure in the male subjects. The activation of reflex micturition, with associated detrusor contractions, resulted in voiding in a significantly larger proportion of female compared to male subjects. A higher urethral outlet resistance is suggested in the male subjects. We conclude that sexual dimorphism of detrusor function is prominent in rhesus macaques, shares many features with the human, and merits consideration in translational and pre-clinical research studies of micturition and LUT function in non-human primates.

scholarly journals Sexual dimorphism in species of Schistura (Teleostei: Nemacheilidae) from the Mae Khlong basin and peninsular Thailand

Zootaxa ◽  
2012 ◽  
Vol 3586 (1) ◽  
pp. 353 ◽  
Author(s):  
RUNGTHIP PLONGSESTHEE ◽  
F. WILLIAM H. BEAMISH ◽  
LAWRENCE M. PAGE
Keyword(s):  
Sexual Dimorphism ◽  
Environmental Factors ◽  
The Other ◽  
Sexually Dimorphic ◽  
Morphometric Characteristics ◽  
Pectoral Fin ◽  
Caudal Fin

Sexually dimorphic characteristics are described for four species of Schistura from the Mae Khlong basin and peninsularThailand. Males of S. mahnerti have a suborbital flap and rows of unculi on the upper surfaces of the pectoral-fin rays.Females of S. mahnerti have a suborbital groove. None of the morphological measurements differ significantly betweenmales and females of S. mahnerti. In the other three species, S. aurantiaca, S. cf. aurantiaca, and S. sexcauda, all indi-viduals lack the flap or groove, but most males have a conspicuous black botch on the procurrent rays of the upper lobeof the caudal fin, a feature absent in most females. Some morphometric characteristics vary between sexes of these spe-cies. Sexually dimorphic traits presumably have a function related to reproduction; however, little is known about reproduction in Schistura, and variation in morphology in relation to habitat or other environmental factors has not been studied.

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