scholarly journals Trypanosoma evansi (Kinetoplastida: Trypanosomatidae) in capybaras (Hydrochoerus hydrochaeris, Rodentia: Hydrochoeridae): prevalence, effect and sexual selection

2017 ◽  
Vol 65 (1) ◽  
pp. 229 ◽  
Author(s):  
Emilio A. Herrera ◽  
Yarlenis Castro
Keyword(s):  
Sexual Selection ◽  
Potential Role ◽  
Trypanosoma Evansi ◽  
Good Genes ◽  
Scent Gland ◽  
Selection Processes ◽  
Hydrochoerus Hydrochaeris ◽  
Males And Females ◽  
Spleen Mass ◽  
Selection Of

Parasites play a crucial role in the ecology of animals. They also appear to be important in mechanisms underlying sexual selection processes. In this article we study the prevalence, effect and potential role in sexual selection of the protozoon Trypanosoma evansi in capybaras, Hydrochoerus hydrochaeris. We collected our samples from the annual capybara cull of a ranch in Venezuela, using the volume of the snout scent gland as an indicator of dominance; the residuals of body weight as indicators of condition; and the residuals of the spleen mass as indicators of immune function. Overall prevalence was 30.9% (N=97) with no difference between males and females and no relation between infection with T. evansi and condition. However, we found that infected animals had larger spleens (residuals), indicating an immunological cost of the infection. Further, males with larger snout scent glands (more dominant) were less likely to be infected than males with smaller glands (less dominant) suggesting that by choosing males with a large gland, females may be using the gland as an indicator of health, which is consistent with the “good genes” view of sexual selection.

Fighting success in relation to body mass and drumming activity in the male wolf spider Hygrolycosa rubrofasciata

1997 ◽  
Vol 75 (9) ◽  
pp. 1532-1535 ◽  
Author(s):  
Janne Kotiaho ◽  
Rauno V. Alatalo ◽  
Johanna Mappes ◽  
Silja Parri
Keyword(s):  
Sexual Selection ◽  
Body Mass ◽  
Wolf Spider ◽  
Male Body ◽  
Male Courtship ◽  
Hygrolycosa Rubrofasciata ◽  
Males And Females ◽  
A Minor ◽  
Selection Of ◽  
Agonistic Encounters

In the wolf spider Hygrolycosa rubrofasciata, males court females by drumming dry leaves with their abdomen. Females prefer to mate with the most actively drumming males, and courtship drumming activity is also positively correlated with male viability. However, body mass of the males seems to have only a minor, if any, effect on female choice or male viability. There is also no correlation between male body mass and courtship drumming activity. We studied the effect of body mass and courtship drumming activity on the outcome of agonistic encounters between male H. rubrofasciata. For this purpose, males and females were randomly placed in a plastic arena, where male courtship drumming activity and agonistic encounters were recorded. Large differences in body mass and drumming activity between two rivals seemed to independently increase the probability of the larger or more active males winning. We conclude that while courtship drumming activity affects the fighting success of the males, and body mass more so, male–male interactions may not be of major importance in sexual selection of H. rubrofasciata.

1. Darwin’s other big idea

2018 ◽  
pp. 1-15 ◽  
Author(s):  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Female Choice ◽  
Egg Production ◽  
Sexual Differences ◽  
The Other ◽  
Sexual Competition ◽  
Sexual Characteristics ◽  
Sexual Selection Theory ◽  
Males And Females ◽  
Selection Of

The idea that males and females often look, sound, smell, and behave differently is uncontroversial. Where those differences came from, however, and what role they play in various species—including humans—is not. ‘Darwin’s other big idea’ outlines Charles Darwin’s sexual selection theory: differential reproduction based on sexual competition, whether between the members of one sex for access to the other, or by selection of particular mating partners. Differences in reproductive parts directly involved in sperm or egg production—primary sexual characteristics—were relatively easy to explain. The other kinds of sexual differences, he proposed, could evolve in one of two ways: male–male competition resulting in weapons, or female choice resulting in ornaments, but this was highly controversial.

scholarly journals A Phylogenetic Perspective on the Evolution of Chromatic Ultraviolet Plumage Coloration in Grackles and Allies (Icteridae)

The Auk ◽  
2006 ◽  
Vol 123 (1) ◽  
pp. 211-234 ◽  
Author(s):  
Muir D. Eaton
Keyword(s):  
Sexual Selection ◽  
Large Body ◽  
Plumage Coloration ◽  
Behavioral Studies ◽  
Evolutionary Force ◽  
Evolutionary Changes ◽  
Phylogenetic Perspective ◽  
Males And Females ◽  
Museum Study ◽  
Selection Of

Abstract Plumage traits have been studied intensely for more than a century, especially bright and exaggerated plumage. A large body of evidence across a range of avian taxa supports sexual selection as a major evolutionary force acting on plumage colors. The discovery of ultraviolet (UV) coloration in avian plumage resulted in the extension of sexual selection hypotheses to explain the evolution of potential UV plumage traits. However, there have been no comparative evolutionary studies elucidating the origin of UV signals in birds. Here, I used a comparative phylogenetic approach to investigate the evolution of chromatic UV plumage colors in the grackles-and-allies clade of the New World blackbirds (Icteridae). On the basis of reflectance data collected from museum study skins, I have determined that UV plumage signals have evolved multiple times from an ancestral condition that lacked UV plumage signals, with very few unambiguous reversals. Although UV plumage has evolved in both males and females, there have been significantly more evolutionary changes in male UV plumage characters. Concentrated changes tests and correlations of independent contrasts reveal evidence for sexual selection of some male UV plumage characters, as well as an increase in UV plumage coloration for species found in open habitats. These results support the use of objective assessments of avian colors (i.e. spectrophotometry) to properly interpret patterns of plumage evolution generally, and they suggest the need for behavioral studies on the function of chromatic UV signals in several blackbird species. Una Perspectiva Filogenética sobre la Evolución de la Coloración Ultravioleta en los Changos y Chamones (Icteridae)

Broad-sense sexual selection, sex gene pool evolution, and speciation

Genome ◽  
1999 ◽  
Vol 42 (6) ◽  
pp. 1033-1041 ◽  
Author(s):  
A Civetta ◽  
R S Singh
Keyword(s):  
Sexual Selection ◽  
Potential Role ◽  
Selection Process ◽  
Broad Sense ◽  
Good Genes ◽  
Secondary Sexual Traits ◽  
Male Characters ◽  
Sexual Conflicts ◽  
Sexual Traits

Studies of sexual selection have traditionally focused on explaining the extreme sexual dimorphism in male secondary sexual traits and elaborate mating behaviors displayed by males during courtship. In recent years, two aspects of sexual selection have received considerable attention in the literature: an extension of the sexual selection concept to other traits (i.e., postcopulatory behaviors, external and internal genital morphology, gametes, molecules), and alternative mechanistic explanations of the sexual selection process (i.e., coevolutionary runaway, good-genes, sexual conflicts). This article focuses on the need for an extension of sexual selection as a mechanism of change for courtship and (or) mating male characters (i.e., narrow-sense sexual selection) to all components of sexuality not necessarily related to courtship or mating (i.e., broad-sense sexual selection). We bring together evidence from a wide variety of organisms to show that sex-related genes evolve at a fast rate, and discuss the potential role of broad-sense sexual selection as an alternative to models that limit speciation to strict demographic conditions or treat it simply as an epiphenomenon of adaptive evolution.Key words: sexual selection, sex-related genes, speciation.

scholarly journals Hyoid Bone Size and Its Implications for Social Organization and Sexual Selection in Alouatta pigra and the Elusive Alouatta macconnelli

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Aubrey R. Whittaker ◽  
Shawn Lehman
Keyword(s):  
Sexual Selection ◽  
Social Organization ◽  
Null Hypothesis ◽  
Hyoid Bone ◽  
Selection Process ◽  
Alouatta Pigra ◽  
Royal Ontario Museum ◽  
The Social ◽  
Males And Females ◽  
Selection Of

The purpose of this research paper is focusing on the hyoid bone in Alouatta pigra and Alouatta macconnelli and determine its role in affecting the social organization and sexual selection of the individuals in these species. This includes the discussion on the dimensions of the hyoid between the males and females as well as an analysis of observed social behaviour patterns and the sexual selection process. It was found that female Alouatta pigra had a larger hyoid than males of the species and that Alouatta macconnelli males had a hyoid nearly twice the size of females. The hyoids were measured from the Mammal Biodiversity collection at the Royal Ontario Museum. The bones dimensions were taken using plastic calipers and their circumference measured using a soft tape measure. Based on the sexual selection and social organisation of Alouatta pigra which is multi-male/multi-female with the occasional unimale with multiple females, the null hypothesis must be accepted as the larger hyoid is not found in males but in females and the size of the hyoid does not affect the social organization in this species. In Alouatta macconnelli, there is little information on this species but the null hypothesis is rejected as males have much larger hyoids than females and the social organization is that of a uni-male with multiple females.

Diagnostic approach to causes of spinal pain

2018 ◽  
pp. 66-70
Author(s):  
F. D. Nasirova
Keyword(s):  
Spinal Pain ◽  
Rapid Loss ◽  
Loss Of Weight ◽  
History Of ◽  
Radiologic Investigation ◽  
Males And Females ◽  
Serious Disease ◽  
Pain At Rest ◽  
Oncologic Diseases ◽  
Selection Of

Causes of spinal pain are extremely varying. Sex composition of patients referring with spinal pain at the age of 16 to 35 was 35% and 65% for males and females, respectively. Peak number of complaints was observed in 30-40 years age group of highest work ability. The followings should be considered as precautions in spinal pain: onset of pain at the age of 20 and after 50, family history of oncologic diseases, walking disorders or dysfunctions of sphincters, numbness in extremities, general malaise and rapid loss of weight, pain at rest and primarily at night, as these conditions may be a warning of underlying serious disease. Selection of algorithm for radiologic investigation is decided by the treating physician.

Reproductive behavior

2018 ◽  
Author(s):  
Rachel Olzer ◽  
Rebecca L. Ehrlich ◽  
Justa L. Heinen-Kay ◽  
Jessie Tanner ◽  
Marlene Zuk
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Female Choice ◽  
Reproductive Behavior ◽  
Mating Systems ◽  
Insect Behavior ◽  
Sequential Approach ◽  
Evolutionary Mechanisms ◽  
Anatomy And Physiology ◽  
Males And Females

Sex and reproduction lie at the heart of studies of insect behavior. We begin by providing a brief overview of insect anatomy and physiology, followed by an introduction to the overarching themes of parental investment, sexual selection, and mating systems. We then take a sequential approach to illustrate the diversity of phenomena and concepts behind insect reproductive behavior from pre-copulatory mate signalling through copulatory sperm transfer, mating positions, and sexual conflict, to post-copulatory sperm competition, and cryptic female choice. We provide an overview of the evolutionary mechanisms driving reproductive behavior. These events are linked by the economic defendability of mates or resources, and how these are allocated in each sex. Under the framework of economic defendability, the reader can better understand how sexual antagonistic behaviors arise as the result of competing optimal fitness strategies between males and females.

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