scholarly journals Confirmation of sexual dimorphism in Hoplias aimara (Valenciennes, 1847) (Erythrinidae: Characiformes) proposed by local expertise in Amapá, Brazil

2014 ◽  
Vol 74 (3) ◽  
pp. 687-690 ◽  
Author(s):  
CS Gama
Keyword(s):  
Sustainable Development ◽  
Sexual Dimorphism ◽  
Traditional Knowledge ◽  
National Park ◽  
Reproductive Strategies ◽  
Biological Information ◽  
Conservation Units ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Formalin Fixed

Fishes may show sexual dimorphism according to their reproductive strategies. In some species, this differentiation is already well known. However, with the findings obtained from recent studies, the number of species for which sex can be determined without dissection has increased. Thus far, the presence of external secondary sexual characteristics in Hoplias aimara, a very well-studied species, has not been reported. Traditional knowledge evidenced through riparian people observations indicated the possibility of sexual dimorphism in this species, which was studied in 2 conservation units, Sustainable Development Reserve of Iratapuru River and Tumucumaque Mountains National Park, in the state of Amapá, Brazil. Fishes were captured, and their anal fins were examined when they were still fresh; the sex of the fishes was confirmed by dissection. The same procedure was used for formalin-fixed fishes. By assessing the shape of the anal fin in fresh or fixed fishes, it was possible to determine the sex of the fish, which was then confirmed by dissection. H. aimara shows sexual dimorphism expressed in the morphology of their anal fin. Thus, the sex of fishes deposited in collections can be identified without any dissection, thereby providing important biological information about the specimens.

scholarly journals Morphometric differentiation and sexual dimorphism in Limnomedusa macroglossa (Duméril & Bibron, 1841) (Anura: Alsodidae) from Uruguay

2021 ◽  
Vol 16 (1) ◽  
pp. 11-25
Author(s):  
Valeria De Olivera-López ◽  
Arley Camargo ◽  
Raúl Maneyro
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Phenotypic Plasticity ◽  
Life History Strategies ◽  
Clinal Variation ◽  
Size And Shape ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Morphological Differences

Intersexual morphological differences within a species occur in many traits, including body size and shape. Many processes that cause geographic variability in morphology have been proposed: population structure, phenotypic plasticity (environmental effects on development), and natural and/or sexual selection. Several hypotheses can explain patterns of sexual dimorphism in anurans, including natural or intra/inter-sexual selection, and differences in life history strategies between sexes. Limnomedusa macroglossa is considered a habitat specialist restricted to rocky outcrops in Brazil, Argentina, Paraguay, and Uruguay. We evaluated the extent of sexual (size and shape) dimorphism in L. macroglossa from Uruguay based on morphometrics and secondary sexual characteristics, while taking into account geographic variation. Sexual dimorphism in body size of adults was found, but multivariate analyses did not demonstrate the existence of significant differences in shape. There were also significant differences in body size and hind leg measurements among six hydrographic basins as a result from the phenotypic plasticity correlated with local temperature, representing a clinal variation along the latitudinal gradient of Uruguay. The sexual dimorphism found in body size is probably the consequence of higher growth rates and/or late sexual maturity in females, which favors larger body size for accommodating larger ovaries, and thus, higher reproductive output. 

scholarly journals Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps

2015 ◽  
Vol 282 (1809) ◽  
pp. 20150342 ◽  
Author(s):  
Solomon Tin Chi Chak ◽  
J. Emmett Duffy ◽  
Dustin R. Rubenstein
Keyword(s):  
Sexual Dimorphism ◽  
Reproductive Skew ◽  
Female Competition ◽  
Single Individual ◽  
Eusocial Insects ◽  
Secondary Sexual Characteristics ◽  
Social Species ◽  
Sexual Characteristics ◽  
Snapping Shrimps ◽  
The Relationship

Sexual dimorphism is typically a result of strong sexual selection on male traits used in male–male competition and subsequent female choice. However, in social species where reproduction is monopolized by one or a few individuals in a group, selection on secondary sexual characteristics may be strong in both sexes. Indeed, sexual dimorphism is reduced in many cooperatively breeding vertebrates and eusocial insects with totipotent workers, presumably because of increased selection on female traits. Here, we examined the relationship between sexual dimorphism and sociality in eight species of Synalpheus snapping shrimps that vary in social structure and degree of reproductive skew. In species where reproduction was shared more equitably, most members of both sexes were physiologically capable of breeding. However, in species where reproduction was monopolized by a single individual, a large proportion of females—but not males—were reproductively inactive, suggesting stronger reproductive suppression and conflict among females. Moreover, as skew increased across species, proportional size of the major chela—the primary antagonistic weapon in snapping shrimps—increased among females and sexual dimorphism in major chela size declined. Thus, as reproductive skew increases among Synalpheus , female–female competition over reproduction appears to increase, resulting in decreased sexual dimorphism in weapon size.

Sex determination and Y chromosome constitutive heterochromatin

2019 ◽  
Vol 1 (1) ◽  
pp. 1-5
Author(s):  
Abyt Ibraimov
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Constitutive Heterochromatin ◽  
Sex Differentiation ◽  
Secondary Sexual Characteristics ◽  
Biological Meaning ◽  
Heterochromatin Block ◽  
Sexual Characteristics ◽  
Open Question ◽  
Efficient Elimination

In many animals, including us, the genetic sex is determined at fertilization by sex chromosomes. Seemingly, the sex determination (SD) in human and animals is determined by the amount of constitutive heterochromatin on Y chromosome via cell thermoregulation. It is assumed the medulla and cortex tissue cells in the undifferentiated embryonic gonads (UEG) differ in vulnerability to the increase of the intracellular temperature. If the amount of the Y chromosome constitutive heterochromatin is enough for efficient elimination of heat difference between the nucleus and cytoplasm in rapidly growing UEG cells the medulla tissue survives. Otherwise it doomed to degeneration and a cortex tissue will remain in the UEG. Regardless of whether our assumption is true or not, it remains an open question why on Y chromosome there is a large constitutive heterochromatin block? What is its biological meaning? Does it relate to sex determination, sex differentiation and development of secondary sexual characteristics? If so, what is its mechanism: chemical or physical? There is no scientifically sound answer to these questions.

scholarly journals The maturity index for Uropodina (Acari: Mesostigmata) communities as an indicator of human-caused disturbance in selected forest complexes of Poland

2021 ◽  
Author(s):  
Agnieszka Napierała ◽  
Jerzy Błoszyk
Keyword(s):  
Soil Quality ◽  
National Park ◽  
Reproductive Strategies ◽  
Nature Reserves ◽  
Maturity Index ◽  
Primeval Forest ◽  
New Methods ◽  
Precise Evaluation ◽  
Białowieża Primeval Forest

AbstractThe necessity of monitoring changes occurring in soil compels us to look for new methods that will allow easy and precise evaluation of the soil quality in a given area. One proposed method is the maturity index (MI) – an index that is based on the distribution of species along the r-to-K continuum in examined populations. In this study, mites from the suborder Uropodina (Acari: Mesostigmata) were examined for their appropriateness in MI-based assessments of soil quality. The first aim of the study was to establish the criteria on the basis of which the evaluation of the r-to-K reproductive strategies was conducted for Uropodina in the examined communities. The second aim was to evaluate the performance of the maturity index of communities of Uropodina as indicator of human-caused disturbance in five areas that are legally protected in Poland. The selected areas were: Białowieża Primeval Forest, Gorce National Park, and three nature reserves: Jakubowo, Las Grądowy nad Mogilnicą, and Cisy Staropolskie im. Leona Wyczółkowskiego. We found that as many as 68 out of the 96 analyzed Uropodina species in Poland are K-stategists. The highest values of the maturity index were recorded for the nature reserves Cisy Staropolskie im. Leona Wyczółkowskiego and the Białowieża Primeval Forest.

Reproductive failure of the red shiner (Cyprinella lutrensis) after exposure to an exogenous estrogen

2010 ◽  
Vol 67 (11) ◽  
pp. 1730-1743 ◽  
Author(s):  
Michelle M. McGree ◽  
Dana L. Winkelman ◽  
Nicole  K.M.  Vieira ◽  
Alan  M.  Vajda
Keyword(s):  
Reproductive Success ◽  
Great Plains ◽  
Endocrine Disrupting Chemicals ◽  
Water Control ◽  
Secondary Sexual Characteristics ◽  
Cyprinella Lutrensis ◽  
The Us ◽  
Sexual Characteristics ◽  
Solvent Control ◽  
17Β Estradiol

Endocrine disrupting chemicals (EDCs) have been detected in surface waters worldwide and can lead to developmental and reproductive disruption in exposed fishes. In the US Great Plains, EDCs are impacting streams and rivers and may be causing adverse reproductive effects. To examine how estrogenic EDCs might affect reproductive success of plains fishes, we experimentally exposed male red shiners ( Cyprinella lutrensis ) to exogenous 17β-estradiol. We characterized the effects of estradiol on male gonadal histology and secondary sexual characteristics, determined whether exposure reduced reproductive success, and examined the effects of depuration. Adults were exposed to a mean concentration of 70 ng·L−1 estradiol, a solvent control, or a water control for at least 83 days. Male exposure to estradiol resulted in elevated plasma vitellogenin concentrations, changes in spermatogenesis, reduced mating coloration and tubercles, altered mating behaviors, and reduced reproductive success with no viable progeny produced. Reproductive endpoints improved upon depuration (28 days). Exposure to estradiol had significant adverse effects on red shiners, indicating that wild populations may face developmental and reproductive difficulties if they are chronically exposed to estradiol.

Comparative urogenital morphology and external sex determination in muskellunge, Esox masquinongy Mitchill

1989 ◽  
Vol 67 (4) ◽  
pp. 1053-1060 ◽  
Author(s):  
Bernard Lebeau ◽  
Gérard Pageau
Keyword(s):  
Ventral Surface ◽  
Northern Pike ◽  
Structural Basis ◽  
Simple Method ◽  
Esox Masquinongy ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Spawning Behaviour ◽  
Accurate Indicator ◽  
Secondary Sexual

Primary and secondary sexual characteristics in northern pike, Esox lucius Linneaus, and muskellunge, Esox masquinongy Mitchill, differ markedly. Differences in the internal urogenital anatomy include the structure of the genital ducts and the angle they form with the ventral surface. Externally, the genital and urinary ducts open directly to the environment in northern pike, whereas in muskellunge they open into a muscular papilla and then through a urogenital pore. Differences in sexual dimorphism between the two closely related esocids constitute a structural basis to explain the known differences in spawning behaviour and reproductive success. Differences in secondary sexual characteristics explain why the methods developed by Demchenko or Casselman to externally sex pike are inapplicable to muskellunge. To develop and test two external sexing techniques for muskellunge, specimens were collected from two regions in Canada from 1980 to 1987. Examination of reproductive products obtained from stripping provided an accurate indicator of sex and sexual maturity, but demonstrated serious limitations. A simple method to sex muskellunge by examination of the external urogenital morphology is described for juveniles and adults. Dissection of fish revealed that with the urogenital examination technique we sexed juveniles with a success rate of 92–98%, and adults with 100% accuracy.

Intersexual and intrasexual selection for neck musculature in men: Attractiveness, dominance, and actual fighting success

2021 ◽  
Author(s):  
Neil Robert Caton ◽  
David M. G. Lewis
Keyword(s):  
Sexual Dimorphism ◽  
Evolutionary Biology ◽  
Theoretical Work ◽  
Human Anatomy ◽  
Geometric Morphometric ◽  
World Region ◽  
Sexual Characteristics ◽  
Neck Strength ◽  
Neck Musculature ◽  
Secondary Sexual

Countless organisms are equipped with physiological armor that reduce damage from opponents. Because humans have sustained a long evolutionary history of hand-to-hand combat, selection would have been placed on morphological structures which reduce rotational acceleration to the head and increase the likelihood of victory. Grounded in over 60 years of sports performance theory and recent theoretical work in evolutionary biology, geometric morphometric analyses revealed that larger neck musculature in professional combatants (N = 715) was associated with greater real-world fighting success, after for adjusting for allometry (Study 1). Because sexual dimorphism emerges from selection on morphological structures that improve men’s fighting success, we then discovered that the human neck is the most sexually dimorphic feature of human anatomy when compared to 91 other anatomical features (N = 6,068; Study 2). This male-biased sexual dimorphism held after controlling for these 91 allometric measurements, and held across every world region (Africa, Asia, Europe, Oceania, and North, Central, and South America). Because human psychological systems consequently evolved to attend to men’s secondary sexual characteristics, we discovered that men (N = 564 stimuli) with larger neck musculature (Study 3: geometric morphometrics; Study 4: physiological neck strength; Study 5: photorealistic stimuli) are rated (N = 772 raters) as stronger, more masculine, and higher in fighting ability and short-term attractiveness, after accounting for allometry. Combined, our research introduced a new secondary sexual characteristic to the biological, anthropological, and psychological sciences: the human neck.

REPLACEMENT ORAL ETHINYLOESTRADIOL THERAPY FOR GONADAL DYSGENESIS: GROWTH AND ADRENAL ANDROGEN STUDIES

1979 ◽  
Vol 91 (3) ◽  
pp. 519-528 ◽  
Author(s):  
Anne W. Lucky ◽  
Samuel P. Marynick ◽  
Robert W. Rebar ◽  
Gordon B. Cutler ◽  
Michael Glen ◽  
...  
Keyword(s):  
Gonadal Dysgenesis ◽  
Bone Age ◽  
Pubic Hair ◽  
Height Velocity ◽  
First Year ◽  
Adrenal Androgen ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Second Year ◽  
Pre Treatment

ABSTRACT We have studied growth and adrenal dehydroepiandrosterone (DHA) responses to iv synthetic adrenocorticotrophic hormone (ACTH, Cortrosyn) in 6 girls with gonadal dysgenesis before and during treatment with lowdose ethinyloestradiol (EOe2). In all patients there was a statisfactory induction of secondary sexual characteristics including increase in breasts and pubic hair and onset of withdrawal bleeding within 6 months of therapy. Height velocity increased from 2.8 ± 0.9 cm/year pre-treatment to 5.3 ± 1.5 cm/year (P < 0.02) in the first year. There was deceleration to 1.9 ± 1.1 cm/year in the second year. There was no disproportionate advancement in bone age and thus, presumably, no loss of ultimate height. We could demonstrate no change in basal or ACTH-stimulated levels of DHA, a specific adrenal androgen, to account for the increased pubic hair and growth in these patients.

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