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Sperm competition

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	Topics Sperm competition Topic Home Sperm competition is "competitionCompetition (biology) Competition within and between species is an important topic in biology, specifically, in the field of ecology.... between spermSperm The term sperm is derived from the Greek word sperma and refers to the male reproductive cells.... of two or more males for the fertilizationFertilization Fertilization , is fusion of gametes to produce a new organism of the same species.... of an ovumOvum An ovum is a haploid female reproductive cell or gamete.... " (Parker 1970). Sperm competition is often compared to having ticketTicket Ticket can mean one of several things:... s in a raffleRaffle A raffle is a competition in which people buy numbered tickets.... ; a male has a better chance of winning (i.e. fathering offspring) the more tickets he has (i.e. the more sperm he inseminates a female with). However, sperm are costly to produce and the energy may be spent elsewhere such as defending a territory to the exclusion of other males; the distribution of resources are called strategies. The optimum amount is the evolutionarily stable strategyEvolutionarily stable strategy In game theory, an evolutionarily stable strategy is a strategy which if adopted by a population cannot be invaded by any c... (ESS). Male fruit flies have been shown to release 250% more sperm when another male is present, compared to being alone with the female . Sperm competition may lead to evolutionEvolution In biology, evolution is the change in the heritable traits of a population over successive generations, as determined by sh... ary adaptations for producing more sperm, such as larger testes. Such adaptations cost and so species with low sperm competition invest in mate competition instead. Other means of sperm competition could include improving the sperm itself or its packaging materials. These sorts of competition can occur within a single male, if they involve genes that are expressed in the haploid sperm itself. The male black-winged damselfly provides a prime example of sperm competition. Female black-winged damselflies are known to mate with several males over the span of a only a few hours and therefore possess a receptacle known as a spermatheca which stores the sperm. During the process of mating the male damselfly will pump his abdomen up and down using his specially adapted penis which acts as a scrub brush to remove the sperm of another male. This method proves quite successful and the male damselfly has been known to remove 90-100 percent of the competing sperm . Sperm competition has led to other adaptations such as larger ejaculates, prolonged copulation, deposition of a copulatory plug, or the application of pheromones that reduce the female's attractiveness. The adaptation of sperm traits, such as length, viability and velocity might be constrained by the influence of cytoplasmic DNA (i.e. mitochondrial DNAMitochondrial DNA Mitochondrial DNA is DNA that is located in mitochondria.... ) . In primates Harcourt et al (1981) studied the relative size of testesTesticle The testicles, or testes , are the male generative glands in animals.... compared to body mass against the mating systemMating system In sociobiology and behavioural ecology, the term mating system is used to describe the ways in which animal societies are s... . They found that promiscuousPromiscuity Promiscuity is the practice of making relatively casual and indiscriminate choices.... chimpanzeeChimpanzee Chimpanzee, often shortened to chimp, is the common name for the two extant species in the genus *Pan.... s have larger testes compared to polygynousFacts About Polygyny The term polygyny* is used in related ways in social anthropology and sociobiology.... gorillaGorilla The gorilla, the largest of the living primates, is a ground-dwelling herbivore that inhabits the forests of Africa.... s. The British biologist Geoffrey ParkerGeoffrey Parker Geoffrey Parker can refer to more than one person:... proposed the concept of sperm competition in a 1970 paper. See also Sperm heteromorphismSperm heteromorphism Overview Sperm heteromorphism is the simultaneous production of two or more distinguishable types of sperm by a single male.... Postcopulatory Reproductive Strategies Cryptic Female Choice External links