No sexual dimorphism in limb muscles of a frog not engaging in amplexus

2013 ◽  
Vol 63 (4) ◽  
pp. 397-405
Author(s):  
Lixia Zhang ◽  
Yunyun Zhao ◽  
Jie Yang ◽  
Xin Lu ◽  
Xiaohong Chen
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Scramble Competition ◽  
Sexual Differences ◽  
Limb Muscle ◽  
Form And Function ◽  
Hindlimb Muscles ◽  
Limb Muscles ◽  
Forelimb Muscles ◽  
And Function

Sexual dimorphism in limb muscles is widespread among anurans, with males having stronger limbs than females. This phenomenon has been interpreted in the context of intrasexual selection: 1) the robust forelimb muscles in males are associated with amplexus, in which the male tries to grasp the female tightly, and also with rejection of rivals’ attempts at taking over, and 2) massive hindlimb muscles favor the ability to kick away rivals during scramble competition. However, in a few species, fertilization occurs without any form of amplexus and in these species the limb muscle dimorphism is expected to be absent. We tested this prediction inFeirana taihangnicus: a species without amplexus. As expected, we detected non-significant sexual differences in the mass of both forelimb and hindlimb muscles after accounting for body size and age. Our findings represent an interesting example of coevolution of form and function.

Reproduction and development

2012 ◽  
Keyword(s):  
Sexual Dimorphism ◽  
Brain Structures ◽  
Sexual Differences ◽  
Tissue Type ◽  
Endocrine Control ◽  
Human Form ◽  
Form And Function ◽  
Sexual Characteristics ◽  
Males And Females ◽  
And Function

Reproduction and development are large topics, knowledge of which underpins several medical specialities including sexual health, fertility, gynaecology, urology, reproductive endocrinology, obstetrics, and neonatology. Doctors need to know the structure, function, and endocrine control of both male and female systems in order to diagnose and manage conditions specific to either male or female organs, as well as conditions such as impotence and infertility. Not surprisingly, the reproductive system is the only body system that shows major differences in both structure and function between males and females. However, sexual differences go beyond the primary sexual characteristics present at birth and the secondary sexual characteristics that emerge under the influence of sex hormones at puberty. Sexual dimorphism in some brain structures commences at an early age, and differences in the endocrine profiles of males and females produce characteristic changes in morphology, physiology, and behaviour that go beyond simple sexual dimorphism to affect many aspects of life, including sexual differences in susceptibility to disease and the longer life expectancy of women as compared to men that is seen around the world. Whether these differences, mainly beneficial to women, are because females are ‘biologically superior’ or because of a complex mix of genetic, behavioural, and social factors is a matter for discussion and research. Some knowledge of embryology is important to every medical student. As a minimum it provides explanations for the congenital malformations and their consequences that are encountered in many areas of clinical practice. Deeper knowledge will assist those seeking real insights into the structure of the human body. It is the study of embryological development and the knowledge of how each tissue type arises, how one tissue meets another, and how tissues move and change shape during development that explains the relations between tissues and organs in the adult human form. Achieving a full understanding of the dynamics of the formation of the body’s organs and tissues is demanding, but it can replace some of the rote learning of anatomical structures, familiar to many students, with a deeper understanding of form and function.

Geographical variation in limb muscle mass of the Andrew’s toad (Bufo andrewsi)

2017 ◽  
Vol 67 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Sheng Nan Yang ◽  
Xiao Fu Huang ◽  
Mao Jun Zhong ◽  
Wen Bo Liao
Keyword(s):  
Geographical Variation ◽  
Biceps Femoris ◽  
Relative Mass ◽  
Flexor Carpi Radialis ◽  
Hindlimb Muscles ◽  
Model Animal ◽  
Limb Muscles ◽  
Forelimb Muscles ◽  
Bufo Andrewsi ◽  
Extensor Carpi Radialis

Muscles are vital for the process of movement, mating and escape of predators in amphibians. During evolution, the morphological and genetic characteristics as well as the size of muscles in species will change to adapt different environments. Theory predicts that low male-male competition in high-altitude/latitude selects for small limb muscles. Here, we used the Andrew’s toad (Bufo andrewsi) as a model animal to test this prediction by analyzing geographical variation in the mass of limb muscles across nine populations from the Hengduan Mountains in China. Inconsistent with the prediction, we found that latitude and altitude did not affect the relative mass of total combined limb muscles and mass of combined hindlimb muscles among populations. Meanwhile, the relative mass of combined forelimb muscles, the two forelimb muscles (flexor carpi radialis and extensor carpi radialis) and the four hindlimb muscles (e.g. biceps femoris, semimebranous, semitendinosus and peroneus) was lowest in middle latitude and largest in low latitude whereas gracilis minor was largest in high latitudes. However, we did not find any correlations between the two forelimb muscles and the four hindlimb muscles and altitude. Our findings suggest that combined forelimb muscles, flexor carpi radialis, extensor carpi radialis, biceps femoris, semimebranous, semitendinosus and peroneus are largest in low latitudes due to pressures of mate competition.

Homoplasy and the evolution of dinosaur locomotion

Paleobiology ◽  
2000 ◽  
Vol 26 (3) ◽  
pp. 489-512 ◽  
Author(s):  
Matthew T. Carrano
Keyword(s):  
Rank Correlation ◽  
Locomotor Apparatus ◽  
Terrestrial Vertebrates ◽  
Form And Function ◽  
Selective Pressures ◽  
Hindlimb Muscles ◽  
Discrete Character ◽  
Avian Hindlimb ◽  
And Function ◽  
The Relationship

In this paper, I survey hindlimb and pelvic anatomy across non-avian dinosaurs and analyze these within a cladistic framework to quantify patterns of change within the locomotor apparatus. Specifically, I attempt to identify where homoplasy constitutes parallelism and may thereby be used to infer similar selective pressures on hindlimb function. Traditional methods of discrete character optimization are used along with two methods for evaluating changes in continuous characters in a phylogenetic context (squared-change parsimony and clade rank correlation). Resultant patterns are evaluated in light of the biomechanics of locomotion and the relationship between form and function in extant terrestrial vertebrates.Although non-avian dinosaurian locomotor morphology is strikingly uniform, these analyses reveal the repeated derivations of several morphological features that have potential relevance for hindlimb locomotor function. Anterior and posterior iliac expansion, a medially oriented femoral head, and an elevated femoral lesser trochanter each evolved independently multiple times within Dinosauria. These changes probably reflect enlargement of several hindlimb muscles as well as a general switch in their predominant function from abduction-adduction (characteristic of “sprawling” limb postures) to protraction-retraction (characteristic of parasagittal, or “erect,” limb postures). Several “avian” characteristics are shared with more basal theropods, and many were acquired convergently in other dinosaurian lineages. The evolution of the avian hindlimb therefore represents a cumulative acquisition of characters, many of which were quite far removed in time and function from the origin of flight.

scholarly journals Ontogenetic scaling of hydrostatic skeletons: geometric, static stress and dynamic stress scaling of the earthworm lumbricus terrestris

1998 ◽  
Vol 201 (12) ◽  
pp. 1871-1883 ◽  
Author(s):  
KJ Quillin
Keyword(s):  
Body Size ◽  
Body Wall ◽  
Dynamic Stress ◽  
Lumbricus Terrestris ◽  
Static Stress ◽  
The Body ◽  
Cross Sectional ◽  
Dynamic Stresses ◽  
Form And Function ◽  
And Function

Soft-bodied organisms with hydrostatic skeletons range enormously in body size, both during the growth of individuals and in the comparison of species. Therefore, body size is an important consideration in an examination of the mechanical function of hydrostatic skeletons. The scaling of hydrostatic skeletons cannot be inferred from existing studies of the lever-like skeletons of vertebrates and arthropods because the two skeleton types function by different mechanisms. Hydrostats are constructed of an extensible body wall in tension surrounding a fluid or deformable tissue under compression. It is the pressurized internal fluid (rather than the rigid levers of vertebrates and arthropods) that enables the maintenance of posture, antagonism of muscles and transfer of muscle forces to the environment. The objectives of the present study were (1) to define the geometric, static stress and dynamic stress similarity scaling hypotheses for hydrostatic skeletons on the basis of their generalized form and function, and (2) to apply these similarity hypotheses in a study of the ontogenetic scaling of earthworms, Lumbricus terrestris, to determine which parameters of skeletal function are conserved or changed as a function of body mass during growth (from 0.01 to 8 g). Morphometric measurements on anesthetized earthworms revealed that the earthworms grew isometrically; the external proportions and number of segments were constant as a function of body size. Calculations of static stresses (forces per cross-sectional area in the body wall) during rest and dynamic stresses during peristaltic crawling (calculated from measurements of internal pressure and body wall geometry) revealed that the earthworms also maintained static and dynamic stress similarity, despite a slight increase in body wall thickness in segment 50 (but not in segment 15). In summary, the hydrostatic skeletons of earthworms differ fundamentally from the rigid, lever-like skeletons of their terrestrial counterparts in their ability to grow isometrically while maintaining similarity in both static and dynamic stresses.

scholarly journals Sexual Dimorphism in Eye Morphology in a Butterfly (Asterocampa leilia; Lepidoptera, Nymphalidae)

2000 ◽  
Vol 103 (1-2) ◽  
pp. 25-36 ◽  
Author(s):  
Kristine S. Ziemba ◽  
Ronald L. Rutowski
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Visual Field ◽  
Surface Area ◽  
Sexual Differences ◽  
Corneal Surface ◽  
Mate Searching ◽  
Eye Morphology ◽  
Eye Size ◽  
Males And Females

In the Empress Leilia butterfly,Asterocampa leilia, as in many insects, males have larger eyes than females. We explore the morphological causes and consequences of this dimorphism in eye size by comparing the corneal surface area, facet numbers, and patterns of variation in facet dimensions in males and females. We report that, with body size (measured by forewing length) controlled, male eyes are consistently larger than female eyes, and that, although males and females do not differ significantly in the number of facets per eye, males have significantly larger facets. Also, males have disproportionately larger facets both frontally and dorsally. As a result of these sexual differences in eye structure, males are expected to have a larger and more acute visual field than females which could be advantageous in the context of this species' mate searching tactic.

Sexual dimorphism modulates the impact of cancer cachexia on lower limb muscle mass and function

2012 ◽  
Vol 31 (4) ◽  
pp. 499-505 ◽  
Author(s):  
Nathan A. Stephens ◽  
Calum Gray ◽  
Alisdair J. MacDonald ◽  
Benjamin H. Tan ◽  
Iain J. Gallagher ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Muscle Mass ◽  
Lower Limb ◽  
Cancer Cachexia ◽  
Lower Limb Muscle ◽  
Limb Muscle ◽  
And Function ◽  
The Impact

Lbx1 is required for muscle precursor migration along a lateral pathway into the limb

Development ◽  
2000 ◽  
Vol 127 (2) ◽  
pp. 413-424 ◽  
Author(s):  
M.K. Gross ◽  
L. Moran-Rivard ◽  
T. Velasquez ◽  
M.N. Nakatsu ◽  
K. Jagla ◽  
...  
Keyword(s):  
Muscle Development ◽  
Muscle Loss ◽  
Limb Muscle ◽  
Lateral Migration ◽  
Muscle Precursor ◽  
Hindlimb Muscles ◽  
Limb Muscles ◽  
Mammalian Embryos ◽  
Myogenic Precursor ◽  
Hypaxial Muscle

In mammalian embryos, myogenic precursor cells emigrate from the ventral lip of the dermomyotome and colonize the limbs, tongue and diaphragm where they differentiate and form skeletal muscle. Previous studies have shown that Pax3, together with the c-Met receptor tyrosine kinase and its ligand Scatter Factor (SF) are necessary for the migration of hypaxial muscle precursors in mice. Lbx1 and Pax3 are co-expressed in all migrating hypaxial muscle precursors, raising the possibility that Lbx1 regulates their migration. To examine the function of Lbx1 in muscle development, we inactivated the Lbx1 gene by homologous recombination. Mice lacking Lbx1 exhibit an extensive loss of limb muscles, although some forelimb and hindlimb muscles are still present. The pattern of muscle loss suggests that Lbx1 is not required for the specification of particular limb muscles, and the muscle defects that occur in Lbx1(−/−) mice can be solely attributed to changes in muscle precursor migration. c-Met is expressed in Lbx1 mutant mice and limb muscle precursors delaminate from the ventral dermomyotome but fail to migrate laterally into the limb. Muscle precursors still migrate ventrally and give rise to tongue, diaphragm and some limb muscles, demonstrating Lbx1 is necessary for the lateral, but not ventral, migration of hypaxial muscle precursors. These results suggest that Lbx1 regulates responsiveness to a lateral migration signal which emanates from the developing limb.

Preservation of Denervated Muscle Form and Function by Clenbuterol in a Rat Model of Peripheral Nerve Injury

2001 ◽  
Vol 26 (4) ◽  
pp. 335-346 ◽  
Author(s):  
A. R. FITTON ◽  
M. S. BERRY ◽  
A. D. McGREGOR
Keyword(s):  
Peripheral Nerve ◽  
Rat Model ◽  
Cross Sectional ◽  
Form And Function ◽  
Hindlimb Muscles ◽  
Adrenoceptor Agonist ◽  
Fast Twitch Muscle ◽  
And Function ◽  
Contractile Forces ◽  
Fast Twitch

The effects of clenbuterol in preserving the form and function of muscle after unilateral sciatic nerve division and epineural repair were investigated in a rat model. The drug (a β2-adrenoceptor agonist) was administered daily for six weeks by gastric gavage (10 μg/kg body weight), interrupted every 5 days by a 2 day omission of dosing to avoid drug desensitization. Clenbuterol reduced the loss of wet weight, total protein, muscle fibre cross sectional area and (in part) contractile forces in denervated hindlimb muscles, with most effects lasting until reinnervation. The effects were dependent on muscle type, with slow-twitch oxidative muscle (soleus) and mixed-fibre (gastrocnemius) showing greater sensitivity to the drug than fast-twitch muscle (extensor digitorum longus). Anabolic effects on the contralateral innervated muscles tended to be small. The results suggest a potential for the adjuvant use of selective β-adrenoceptor agonists in the management of peripheral nerve injuries in humans.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

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