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 ?
Murata K (2003) Blocks to polyspermy in fish: a brief review.
Structures were classified as non-fertilized (absence of sperm and/or male pronucleus); correctly fertilized (presence of two polar bodies and two (male and female) pronuclei); or improperly fertilized (presence of polyspermy, of more than two pronuclei).
Shioya, "Development of the competence of bovine oocytes to release cortical granules and block polyspermy after meiotic maturation," Development Growth & Differentiation, vol.
By the early 20th century, fertilization researchers realized that the sperm cell not only delivers a haploid nucleus to the egg but also somehow signals or activates the egg cell to prepare for embryogenesis (in mammals, egg activation events include creation of the polyspermy block and completion of meiosis).
Also available was one of his strap-on "Spukakki" machines (think bukkake, involving a woman being ejaculated on by a group of men) that shot scalding wax all over the floor, and assorted throw rugs, furniture, photographs, wide-eyed visitors, and miniature ceramic donkey carts supporting freshly scented homemade candles, alluding to a kind of bestial bukkakephous polyspermy.
Schatten, "Microtubule Organization in the Cow During Fertilization, Polyspermy, Parthenogenesis, and Nuclear Transfer: The Role of the Sperm Aster," Developmental Biology 162 (1994): 29-40.
Polyspermy versus unreduced male gametes as the origin of nonaploids (9x) common wheat plants.
Polyspermy blocks in fucoid algae and the occurrence of polyspermy in nature.
The sperm's penetration of the egg, in addition to stimulating the egg's "sperm blocking" mechanism that prevents polyspermy, also initiates a series of changes that leads to a release of sequestered calcium ions, which in turn start the mechanisms producing the first cell's cleavage.
Zona hardening prevents subsequent sperm from also fertilizing the egg -- a phenomenon called polyspermy -- which would result in an overabundance of DNA in the developing egg and in most cases cell death.
During the spawning event, appropriate sperm-to-egg ratios were observed to prevent polyspermy and potential abnormal larval development.