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. 

The effects of phthalate and nonylphenol exposure on body size and secondary sexual characteristics during puberty

2015 ◽  
Vol 218 (7) ◽  
pp. 603-615 ◽  
Author(s):  
Jia-Woei Hou ◽  
Ching-Ling Lin ◽  
Yen-An Tsai ◽  
Chia-Huang Chang ◽  
Kai-Wei Liao ◽  
...  
Keyword(s):  
Body Size ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Secondary Sexual

scholarly journals Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

2001 ◽  
Vol 72 (1) ◽  
pp. 17-31 ◽  
Author(s):  
JAY F. STORZ ◽  
J. BALASINGH ◽  
HARI R. BHAT ◽  
P. THIRUCHENTHIL NATHAN ◽  
D. PARAMANANTHA SWAMI DOSS ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Clinal Variation ◽  
Fruit Bat ◽  
Cynopterus Sphinx

Heads or tails? Sexual dimorphism in helodermatid lizards

2007 ◽  
Vol 85 (1) ◽  
pp. 92-98 ◽  
Author(s):  
C.M. Gienger ◽  
Daniel D. Beck
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Morphological Traits ◽  
Tail Length ◽  
Repeated Sequences ◽  
Analysis Of Covariance ◽  
Head Size ◽  
Heloderma Suspectum

We tested the hypothesis that helodermatid lizards (Gila monsters, Heloderma suspectum Cope, 1869, and beaded lizards, H. horridum (Wiegmann, 1829)) show sexual dimorphism in morphological traits related to male–male agonistic behaviors. Male–male combat in helodermatid lizards involves repeated sequences of ritualized grappling. Male Gila monsters use their heads in attempts to gain or maintain a superior position during repeated combat bouts that may last for hours. Pairs of fighting male beaded lizards form spectacular body arches, with abdomens adpressed and snouts, forelimbs, and tail tips contacting the ground. We measured body size, head size, and tail length in 208 preserved H. suspectum, and body size and tail length (but not head size) in 79 live H. horridum, then tested for sexual dimorphism using analysis of covariance. Male Gila monsters had proportionately larger heads than females but did not differ in tail length or body size. Male beaded lizards had proportionately longer tails than females and were larger in body size only when the largest individuals were included in the analysis. Differences in head dimensions (in H. suspectum) and tail length (in H. horridum) are likely the result of sexual selection acting through male–male agonistic behaviors in this unique lizard taxon.

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 Sexual dimorphism in Apfelbeckia insculpta (L. Koch, 1867) (Myriapoda: Diplopoda: Callipodida)

2017 ◽  
Vol 69 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Bojan Ilic ◽  
Bojan Mitic ◽  
Slobodan Makarov
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Endemic Species ◽  
Balkan Peninsula ◽  
Body Plan ◽  
Body Proportions ◽  
Adult Body ◽  
Copulation Behavior

Apfelbeckia insculpta (L. Koch, 1867) is one of the largest European millipedes and an endemic species of the Balkan Peninsula. We present data on sexual dimorphism in size and body proportions obtained from 179 adult specimens of this species from four caves in Serbia and one in Montenegro using univariate and multivariate morphometric techniques. Sexual dimorphism was apparent and female-biased for all measured characters, except for lengths of the antennae and the 24th leg pair (which were larger in males) and lengths of the first, second and fourth leg pairs, which exhibited small differences between sexes. Generally, females had significantly greater body size than males, while males expressed significantly greater values in traits that can be associated with mobility and copulation behavior. Also, we found significant variations in sexual size and body proportions dimorphism among analyzed populations. The influences of fecundity and sexual selection on the adult body plan in A. insculpta are discussed.

Sexual Selection on Body Size and Shape in the Western Harvester Ant, Pogonomyrmex occidentalis Cresson

Evolution ◽  
1999 ◽  
Vol 53 (2) ◽  
pp. 535 ◽  
Author(s):  
Allison J. Abell ◽  
Blaine J. Cole ◽  
Ruth Reyes ◽  
Diane C. Wiernasz
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Size And Shape ◽  
Pogonomyrmex Occidentalis ◽  
Harvester Ant

Sexual dimorphism in thick-billed murres, Uria lomvia

1993 ◽  
Vol 71 (2) ◽  
pp. 346-351 ◽  
Author(s):  
Donald T. Stewart
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Discriminant Analysis ◽  
Driving Force ◽  
Mate Guarding ◽  
Canonical Discriminant Analysis ◽  
Uria Lomvia ◽  
Breeding Sites ◽  
Univariate Statistics

The pattern of sexual dimorphism in thick-billed murres, Uria lomvia, from the Lancaster Sound – Jones Sound region, Northwest Territories, was examined for weight and 21 skeletal characters. Univariate statistics (Bonferroni-corrected t-tests) indicated that males were significantly larger than females in 6 bill and skull characters. Multivariate statistics also indicated that males had larger bills and skulls than females (based on canonical discriminant analysis), but males were not larger than females in overall body size (as defined by the first principal-components axis). The direction and magnitude of dimorphism were consistent with a hypothesis based on sexual selection as the driving force. In particular, large bill and skull sizes in males are consistent with agonistic behaviours associated with male–male competition for breeding sites and mate guarding.

scholarly journals Sex-specific predation risk and the evolution of sexual dimorphism in immunocompetence: a theoretical analysis

2014 ◽  
Author(s):  
Benjamin Fanson ◽  
Eirik Søvik
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Sexual Dimorphism ◽  
Immune Function ◽  
Predation Risk ◽  
Reproductive Effort ◽  
Life History Strategies ◽  
Defense Strategies ◽  
Differential Predation ◽  
Predation Costs

Sexual dimorphism in immunocompetence, with males having lower immune function, is a prevalent pattern in nature. The main evolutionary explanation for this pattern is that males preferentially allocate resources away from immune function and towards reproductive effort to increase their competitiveness for limited females. However, the role of differential predation risk between the sexes has not been considered, despite predation risk being a major driver of life history strategies and male sexual traits often having associated predation costs. It is unclear whether increased predation risk should increase or decrease investment in immune function, as males have been shown to utilize both behavioural (e.g. decrease foraging activity) and/or life-history (e.g. decrease investment in sexual trait) defense strategies to manage predation risk. Here, we modelled optimal resource acquisition and allocation towards immune function under differential predation risk with multiple defense strategies. If males have limited defense strategies, increasing predation risk caused males to trade-off immune function for reproductive effort, leading to reduced immunocompetence. In contrast, if males can only decrease predation risk through reduction of reproductive effort (e.g. decrease colouration or calling rates), then increasing predation risk causes immune function to increase. If males can utilize multiple defense strategies and sexual selection is low, then males maintain a constant immune function as predation risk increases. Sexual selection robustly resulted in decreased immunocompetence. Overall, our results suggest that predation plays an important role in the evolution of sexual dimorphism in immunocompetence, but predicting its effect requires understanding the integrated defense strategies available.

Masculinized females in a population of Leptodiaptomus minutus (Copepoda, Calanoida)

1998 ◽  
Vol 76 (3) ◽  
pp. 596-600 ◽  
Author(s):  
Kristine B Sillett ◽  
Richard S Stemberger
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Adult Males ◽  
Secondary Sexual Characteristics ◽  
Adult Females ◽  
Internal Morphology ◽  
Sexual Characteristics ◽  
The Common ◽  
Normal Males ◽  
Normal Adults

In a population of the common freshwater copepod Leptodiaptomus minutus Lilljeborg, 7.3% of adult females exhibited male secondary sexual characteristics. Although these masculinized or intersex females had the internal morphology of normal females, they possessed one or rarely two normal geniculate male antennules, and in a few instances male fifth legs. The sex ratio of normal adult males to females in the population was 1:1. No differences in body size among normal males, normal females, and masculinized females were found. Antennule lengths of males and masculinized females were not significantly different from one another; however, normal females had longer antennules than either males or masculinized females. Mating experiments indicated that masculinized females were functionally female and they were able to mate with normal males to produce offspring that were normal or masculinized. The occurrence of intersex copepods in lakes of North America may be more widespread than we now recognize because they can be easily overlooked or mistaken for normal adults.

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