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The entry of several sperm into one ovum during fertilization.

pol′y·sper′mic adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
References in periodicals archive ?
The researchers said that this defensive response could help prevent polyspermy, which happens when the egg is fertilized by more than one sperm and cannot develop. 
Izumo meets Juno: preventing polyspermy in fertilization.
The results indicate that (1) males with white spines achieved higher fertilization and were more likely to cause polyspermy than males with purple spines, and there was no effect of female spine color on fertilization; (2) when comparing the average success of individual matings with pooled-sperm matings, there was a net benefit to polyandry when purple-spine males were pooled, a net cost when white-spine males were pooled, and no difference when mismatched spine color males were pooled; and (3) the success under pooled-sperm trials, with any of the spine color combinations, never exceeded the success of the more successful male in the individual-male trials.
In animal species, this technique has several applications such as avoidance of the polyspermy problem (e.g.
Fertilization in fishes and the problem of polyspermy. Acad.
In teleosts, the cortical alveoli content is released into the perivitelline space, at the moment of fertilization, blocking polyspermy and contributing to chorion hardening (Hart, 1990).
A teleost egg is covered with a thick envelope called a chorion, which has a narrow pore designated as a micropyle that helps to avoid polyspermy [15].
Parrish [30], states that the number of sperm added to oocytes during IVF affects the percentage of oocytes penetrated and even increase polyspermy rate.
MYO is an important constituent of follicular microenvironment and it plays a determinant role in both nuclear and cytoplasmatic oocyte development [9], being also a precursor of phospholipids, which are responsible for the generation of important intracellular signals oocytes such as release of cortical granules, inhibition of polyspermy, and resumption of meiotic process [10].
It was found that to block polyspermy in sea urchins, biological transformation of the egg cellular matrix could be done, resulting in the formation of a fertilization envelope (solid structure).
One of the determining factors for the low efficiency of porcine embryo IVP is the elevated rate of polyspermy (TOKESHI et al., 2007; FAUSTINI et al., 2010).