________________________________________________________________________________ Abstract The aim of the study was to determine if the breeding potential of 25-month old Bonsmara beef bulls could be predicted from production characteristics. Forty-one Bonsmara bulls were included in an on-farm performance test (also known as the Phase D growth test) for a period of 180 days. At an average age o...

Inbreeding depression, or the reduction in fitness due to mating between close relatives, is a key issue in biology today. Inbreeding negatively affects many fitness-related traits, including survival and reproductive success. Despite this, very few studies have quantified the effects of inbreeding on vertebrate gamete traits under controlled breeding conditions using a full-sib mating approach...

In 2007, the Intergovernmental Panel on Climate Change projected an average global air temperature increase of 1.1-6.4°C by the end of the 21st century. Although the tropics are predicted to experience less extreme temperature increases than regions of higher latitude, tropical ectotherms live close to their thermal limits, and are thus particularly vulnerable to increases in temperature. In th...

Sperm morphology was evaluated (using Blom classification) in 44 ejaculates of 11 bulls and 44 ejaculates of 11 boars. Significant differences in sperm morphology were found between bulls and boars. In addition, the correlations between frequency of morphological changes and morphometrical traits of boar spermatozoa were demonstrated. More morphological anomalies of spermatozoa were recorded in...

From 1913 to 1916, Calvin Bridges performed experiments that indicated genes [5] are found on chromosomes. His experiments were a part of his doctoral thesis advised by Thomas Hunt Morgan [6] in New York, New York. In his experiments, Bridges studied Drosophila [7], the common fruit fly, and by doing so showed that a process called nondisjunction caused chromosomes, under some circumstances, to...

Sperm competition may select for male reproductive traits that influence female mating or oviposition rate. These traits may induce fitness costs to the female; however, they may be costly for the males as well as any decrease in female fitness also affects male fitness. Male adaptations to sperm competition manipulate females by altering not only female behaviour or physiology, but also female...

Surveys of inbred strains of mice are standard approaches to determine the heritability and range of phenotypic variation for biomedical traits. In addition, they may lead to the identification of novel phenotypes and models of human disease. Surprisingly, male reproductive phenotypes are among the least-represented traits in the Mouse Phenome Database. Here we report the results of a broad sur...

It is now well-established that reproduction in wildlife can be disrupted by anthropogenic environmental changes, such as chemical pollution. However, very little known about how these pollutants might affect the interplay between pre- and post-copulatory mechanisms of sexual selection. Here, we investigated impacts 21-day exposure male eastern mosquitofish (Gambusia holbrooki) to a field-reali...

Spermatogenesis and sperm maturation are complex processes which are affected by a myriad of endocrine, paracrine and neural factors. In birds, regulation of testicular and excurrent duct growth, maturation and function are only poorly understood. As the quality and quantity of sperm produced may be altered at any of several points during sexual maturation, spermatogenesis or during extragonada...

Sexual selection is considered a potent evolutionary force in all sexually reproducing organisms, but direct tests in terms of experimental evolution of sexual traits are still lacking for simultaneously hermaphroditic animals. Here, we tested how evolution under enforced monogamy affected a suite of reproductive traits (including testis area, sex allocation, genital morphology, sperm morpholog...