| Summary: | Sperm competition is an important feature of the reproductive biology of numerous species. Among taxa in which females are polygamous and have sperm storage organs (i.e. spermathecae), mechanisms of sperm competition often favour single paternity and may fall into two broad cat egor ies , cal l ed sperm stratification and sperm removal. In the former, sperm from the last male displaces previous ejaculates toward the end of the spermatheca, away from efferent ducts leading to the ovary and may be the first used in fertilizing eggs. Removal of sperm, on the other hand, involves elimination of previously deposited sperm from the female reproductive tract, either by direct extraction or indirectly by "flushing out" one ejaculate by a subsequent one.[.]
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