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Polyspermy
In biology, polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy, on the other hand, contains three or more copies of each chromosome—one from the egg and one each from multiple sperm. Usually, the result is an inviable zygote. This may occur because sperm are too efficient at reaching and fertilizing eggs due to the selective pressures of sperm competition. Such a situation is often deleterious to the female: in other words, the male-male competition among sperm spills over to create sexual conflict.〔Arnqvist, G. & Rowe, L. (2005) ''Sexual conflict''. Princeton University Press, Princeton ISBN 0-691-12217-2〕
==Chicken and zebra finch eggs require multiple sperm==
In the journal Proceedings of the Royal Society B, as reported in the New York Times, Dr. Nicola Hemmings, an evolutionary biologist at the University of Sheffield, and one of the study’s authors, reported that eggs of zebra finches and chickens require multiple sperm, from 10 to hundreds of sperm, to penetrate the egg to ensure successful fertilization and growth of the bird embryo.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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