ڵλã ŦԼʱӢ >> ŦԼʱӢİ >> ѧ >> 


ʱ:2015-10-26 18:22:35 Դ:ŦԼʱ :

A Mothers Ability to Reproduce All by Herself

Q. I read that some wild snakes gave birth without mating. How does such a virgin birth work?


A. The development of offspring from unfertilized egg cells is called parthenogenesis.


It is common in many invertebrate species that have two sexes for reproduction to occur without input from a male representative. Instead of combining with a male germ cell to form a gamete with half of its DNA from each parent, an egg cell gives rise to the gamete and embryo stages on its own.


Only since the late 1800s has it become known that such asexual reproduction also occurs in some vertebrates, including snakes, lizards like the endangered Komodo dragon, birds and even sharks.


Such births were documented only in captive representatives of these species, like zoo specimens and domestic fowl. Although these births have not been seen in the wild, a 2012 study found strong suggestive evidence that they do in fact happen. The report, in the journal Biology Letters, involved two closely related species of snakes, the copperhead and the cottonmouth.

׼¼ֻڱȦУ綯԰ĶͼݡδҰⷢ2012һо֣֤ݱʵǴڵġڡѧͨѶ(Biology Letters)ϵĸñ漰ֹϵеߣֱͭͷߺ޿ߡ

The offspring of two pregnant females collected in the wild showed genetic characteristics that were identical to those of the mothers. The likelihood of this happening if mating had occurred, adding paternal DNA identical to the maternal contribution, is infinitesimally small, the researchers said. They concluded that their findings represented the first cases of such parthenogenesis found in the wild.