Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg  during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring.
Performed the experiments: SL. The authors confirm that all data underlying the findings are fully available without restriction. In species where females mate with multiple males, the sperm from these males must compete to fertilise available ova.
Sperm competitiona special form of mating competition that occurs in sexual species when females accept multiple mating partners over a relatively short period of time. The potential for overlap between the sperm of different males within the female has resulted in a diversity of behavioral adaptations and bizarre strategies for maximizing paternity. Sperm competition is thought to be the primary reason why males offer nuptial gifts such as food to females or allow females to cannibalize them.
The ubiquitous occurrence of sperm selection mechanisms throughout nature, some depending upon the self-selective propensities of spermatozoa while others involve antagonistic selection imposed by the female reproductive system, has stimulated considerable theoretical interest and debate for many years. Evolutionary biologists have developed several hypotheses that link sperm selection to the inheritance of superior fitness traits i. In this review we examine the value of sperm function tests in the context of the biological issues involved to see how much guidance can be gleaned from the natural selection processes.
The influence of sperm competition upon sperm size has been a controversial issue during the last 20 years which remains unresolved for mammals. The hypothesis that, when ejaculates compete with rival males, an increase in sperm size would make sperm more competitive because it would increase sperm swimming speed, has generated contradictory results from both theoretical and empirical studies. In addition, the debate has extended to which sperm components should increase in size: the midpiece to accommodate more mitochondria and produce more energy to fuel motility, or the principal piece to generate greater propulsion forces.
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Sperm competition is defined as the competition between sperm from at least two males for the fertilization of a given set of eggs. It has been established as a powerful evolutionary force driving and influencing many different aspects of evolutionary biology and behavioral ecology, including sexual selection and sexual conflict, the evolution of mating systems, speciation and reproductive isolation, and the evolution of anisogamy. It is a field of research that is still relatively young, but it has received ample attention and researchers have greatly contributed to understanding the causes and consequences of sperm competition by developing extensive theoretical work, with seminal articles summarized under Sperm Competition in Theory and a large body of empirical studies in a wide range of taxonomic groups employing a wide range of empirical tools.
A MALE whose sperm has to compete with the sperm of other males reacts by producing more sperm each time he ejaculates. Their work Animal Behaviour, vol 37, p confirms a prediction of the theory of sperm competition, an idea which explains why males of some species have big testes while others have small ones compared to their body size. Sperm competition theory predicts that if several males copulate with each female in oestrus, as in chimpanzee societies for instance, then their sperm will have to compete for fertilisation in the female reproductive tract. In the long term, therefore, evolutionary selection will favour increased production of sperm and bigger testes.