Monday, September 17, 2012

Virgin Births May Be Common in the Wild

Parthenogenesis is asexual reproduction that occurs in bisexual species. Examples of parthenogenesis have been observed before in species held in captivity.  It is most commonly observed in invertebrates but occasionally in vertebrates as well, specifically the Komodo dragon, sharks and some birds.

In this study, genetic samples from mothers and their offspring were collected from 22 litters of wild copperhead snakes from Connecticut and 37 litters of wild cottonmouth snakes from Georgia. After analyzing the DNA of these snakes, researches discovered homozygous maternal alleles across all loci in both species’ offspring. In other words, “the offspring were solely the product of the mother, with no genetic contributions from the father”. What was even more surprising to the researchers was the frequency - between 2.5% and 5% of offspring in these species may be a result of parthenogenesis.

Parthenogenesis occurs during meiosis when sex cells are dividing. Because the sex cells only contain half the genetic material necessary to create offspring, pairs of sex cells in the snakes (and other species that undergo parthenogenesis) fuse together. Embryos then form from the mother’s fused sex cells. These offspring, however, are not clones of their mother because the sex cells that fused were not “identical halves of her genome”.

Before this study, scientists had only observed parthenogenesis in animals held in captivity. This study was important because it was conducted on wild snakes, revealing that parthenogenesis is in fact, not “a captive syndrome”. Even when able to mate with a male, some within these species still reproduced via parthenogenesis. Going forward, scientists are hoping to expand their research to more species, such as water snakes in Oklahoma. Scientists are also curious in following the offspring of virgin births to see how they survive and reproduce.


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