Polyembryony


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Related to Polyembryony: apomixis

polyembryony

[¦päl·ē·im′brī·ə‚nē]
(zoology)
A form of sexual reproduction in which two or more offspring are derived from a single egg.

Polyembryony

 

in animals, the formation of several embryos (twins, triplets) from a single zygote. Monovular offspring are always of the same sex. A distinction is made between specific polyembryony (normally characteristic of a given species) and sporadic, or occasional, polyembryony. Specific polyembryony characterizes some bryozoans, parasitic hymenopterans and strepsipterans, and armadillos. A striking example is the formation from one zygote of as many as 3,000 larvae in flies of the genus Litomastix. In the armadillo Dasypus hybridus Desmarest, seven to nine embryos, each having its own amnion but sharing a common chorion, develop from a single ovum. Sporadic polyembryony is observed in all animals, but it is especially frequent in some hydrozoan polyps and earthworms. In vertebrates it results from the division of the embryo into several parts, usually before or at the onset of gastrulation. In human sporadic polyembryony, two to five offspring of the same sex are born. Polyembryony has been produced experimentally in many animals by various means.

REFERENCES

Kanaev, I. I. Bliznetsy. Moscow-Leningrad, 1959.
Ivanova-Kazas, O. M. “Poliembrioniia u zhivotnykh.” Arkhiv anatomii, gistologii i embriologii, 1965, vol. 48, issue 3.
Tokin, B. P. Obshchaia embriologiia [2nd ed.]. Moscow 1970.

A. V. IVANOV and K. M. KURNOSOV

In plants, polyembryony is the formation of several embryos in a single seed. They may arise in a single embryo sac (true polyembryony) or in different ones (false polyembryony). With true polyembryony, several embryos develop from a single zygote as a result of the zygote’s irregular division (for example, in some tulips) or as a result of delamination of the proembryo or the proembryo’s apical cell (in the European yellow water lily). They may also develop from cells of the suspensor (in Lobelia). Often in true polyembryony the embryo arises from one or two synergids (in iris, lily, and mimosa) or antipodes (Allium odorum). Additional embryos may arise without fertilization from cells of the nucellus and the integuments. With false polyembryony, the embryo is formed either as a result of development of several embryo sacs in the ovule (strawberry, pyrethrum) or the development of not only one of the four megaspores, as usual, but of several (in lilies and lady’s mantle). It may also form owing to the development of supplementary aposporous embryo sacs (from vegetative cells) and a normal sac (in hawkweed and wormwoods).

REFERENCES

Maheshwari, P. Embriologiia pokrytosemennykh. Moscow, 1954. (Translated from English.)
Poddubnaia-Arnol’di, V. A. Obshchaia embriologiia pokrytosemennykh rastenii. Moscow, 1964.

L. V. KUDRISHOV

References in periodicals archive ?
Polyembryony is the splitting of a single product of sexual reproduction (zygote, embryo, or larva) into multiple offspring with identical genotypes.
Loss of polyembryony as a normal seed developmental feature: as in Torreya (Coulter & Land, 1905).
The two species presented only one embryo per seed and no polyembryony was recorded.
com, or MSN Live Search, find more information by searching for these words or phrases: after riping, dioecious, generative cell, integument, microsporangia, microspore mother cell, nucellus, ovule, polyembryony, seed coat, self-incompatible, and tube cell.
Nine-banded armadillos exhibit obligate polyembryony, whereby they produce litters of genetically identical quadruplets by repeated twinning of a single fertilized egg.
Andrade-Rodriguez M, Villegas-Monter A, Carrillo-Castaneda G, Garcia-Velasquez A (2004) Polyembryony and identification of volkamerian lemon zygotic and nucellar seedlings using RAPD.
10) A condition known as polyembryony where the embryos possess separate amniotic sacs but are enclosed within a common chorion, see W.
Nine-banded armadillos (Dasypus novemcinctus) and other members of this genus are the only vertebrates that routinely exhibit monozygotic polyembryony or giving birth to genetically identical offspring (Newman and Patterson, 1910; Newman, 1913; Prodohl et al.
Gynodioecy, polyembryony, and partial asexuality (vegetative reproduction) have all been suggested as candidate systems that could potentially have this effect (Lande et al.
The development of the nine-banded armadillo from the primitive streak stage to birth: with especial reference to the question of specific polyembryony.