Polyspermy

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polyspermy

[′päl·ē‚spər·mē]
(physiology)
Penetration of the egg by more than one sperm.

Polyspermy

 

(1) In animals, the fertilization of an ovum by several spermatozoa. Two types of polyspermy are distinguished: physiological and pathological.

Physiological polyspermy is characteristic of several groups of animals with internal insemination: spiders, insects, fishes of the class Chondrichthyes, amphibians of the order Caudata, reptiles, and birds. In such animals, the number of spermatozoa penetrating the ova varies from one or two to 12 in insects and numbers several dozen in chordates. In the ooplasm all the spermatozoa change similarly: their heads become spermatic nuclei. The nucleus nearest to the female pronucleus merges with it and forms a syncaryon, which proceeds to the stage of cleavage. The remaining spermatic nuclei also begin the process of mitosis, but in insects, caudates, and reptiles the process is blocked and the mitotic figures are soon resorbed.

Among birds, the spermatic nuclei divide repeatedly and degenerate at the stage of eight to 16 blastomeres. Among Chondrichthyes, the spermatic nuclei divide many times and are gradually ousted by the segmentation nuclei, the offspring of the syncaryon, beyond the boundaries of the embryonic disk; thus, they do not participate in the formation of the body of the embryo. The suppression of mitosis and the resorption of all the spermatic nuclei except one are caused by changes in the properties of the cytoplasm of the fertilized ovum, whose nature is as yet unknown.

Pathological polyspermy occurs among physiologically mono-spermous animals having external and in some groups, including mammals, internal insemination. When there is an excessive concentration of spermatozoa or when the ova are in poor physiological condition, the mechanisms ensuring normal monospermy are insufficiently effective and each ovum may be penetrated by several spermatozoa. These spermatozoa take part in the embryo’s development and cause profound disturbances; the embryo soon dies.

REFERENCES

Rothschild, N. M. V. Oplodotvorenie. Moscow, 1958. (Translated from English.)
Ginzburg, A. S. Oplodotvorenie u ryb iproblema polispermii. Moscov, 1968.

A. S. GINZBURG

(2) In plants, the penetration of more than one spermatozoon, usually two, into the ovum and the secondary nucleus of the embryonic sac, irrespective of the subsequent fate of the spermatozoa.

References in periodicals archive ?
Although high polyspermic penetration rates are well documented in pigs (FUNAHASHI 2003; SUZUKI et al., 2003), some interesting interactions of oocyte quality and the sire have been reported in cattle (OHLWEILER et al., 2013), where depending on the technique used to artificially fertilize the oocyte, the embryo development rate was affected or not by the oocyte quality.
The researchers obtained forty-eight blastomeres from the seventeen polyspermic embryos (eight two-cell, two three-cell, five four-cell, and two eight-cell), or theoretically forty-eight new totipotent embryos.
The proportion of polyspermic oocytes (10-40%) also varied according to the bulls (p<0.05).
Modulation of the function of boar spermatozoa via adenosine and fertilization promoting peptide receptors reduce the incidence of polyspermic penetration into porcine oocytes.
In both species, the correlation coefficients for the relationship between logit (P) and [log.sub.10]sperm density increased proportionally with gamete contact time (Table 1), but the relationship broke down at longer contact times (i.e., [greater than or equal to] 1,200 s in blacklip abalone and [greater than or equal to] 480 s in greenlip abalone) because of a reduction in the data set (i.e., zero scores from polyspermic trials were omitted).
Because this method bypasses the normal zona-closing mechanism, it sometimes allows more than one sperm to penetrate the egg membrane, creating a "polyspermic" egg that can't develop properly and must be discarded.
Growth retardation of inner cell mass cells in polyspermic porcine embryos produced in vitro.
When even higher sperm concentrations were used to increase polyspermic eggs, all incorporated sperm left distinct GSII basal rings on the surface of the egg.
The ratios of polyspermic invasion were not different among HSP70 of the three genotypes.
Polyspermic eggs, fertilized with a higher than average concentration of sperm in solution, formed wrinkles (Fig.
However, the percentage of polyspermic oocytes in the sperm concentration of 2.5 x [10.sup.5] sperm/ml was lower than in concentrations of 5, 10 and 20 x [10.sup.5] sperm/ml.