![]() Genetic testing technology that can identify parthenogenesis more readily is helping researchers discover that more and more species are capable of virgin births. ![]() Although many invasive species are bigger and stronger than the locals, parthenogenesis is another factor that can contribute to their success. It invaded many European waterways by reproducing asexually. The spiny-cheek crayfish is native to the US but was introduced to Europe where the climate is more moderate. For example, many cases of parthenogenesis have been discovered in geckos, snakes and lizards that live in dry and harsh climates such as high altitudes.įemale animals can also reproduce asexually to take advantage of a favourable change in conditions. If environmental conditions are poor, asexual reproduction involves less effort than sexual reproduction, because the female doesn’t need to waste time and energy finding a mate. Perhaps the female simply didn’t fancy the males she lived with. For example, last year a female zebra shark hatched several young with DNA that did not match any of the males in the Chicago aquarium where she lived, baffling researchers. Passing on genesĮven when there are males around, females may still use parthenogenesis. This is often reported in captive animals, including the bonnethead shark, where animals are kept in single-sex enclosures. For example, when there aren’t many males around. Virgin birth, which usually results in female offspring, is thought to be triggered in several situations. They rely mainly on sexual reproduction, but can use asexual reproduction if necessary. Some species, termed facultative parthenogens, alternate between sexual and asexual reproduction. Not only do they lack the genetic diversity of organisms created in sexual reproduction but they only inherit half of their mother’s genetic diversity. So half clones have even less genetic diversity than full clones. Full clones are created when an embryo multiples whole cells. Half clones are produced when embryonic cells split in half before multiplying. Parthenogenic young can be either full or half clones of the mother. It won’t necessarily be genetically identical to the mother though – this depends on how the egg cell develops. Virgin births, known as parthenogenesis, happen when an unfertilised egg develops into an embryo. Unfertilised eggs are often produced by females – you may have had unfertilised eggs for breakfast this morning from a domestic hen – and if unfertilised eggs aren’t eaten, they eventually perish. But, unlike other forms of asexual reproduction, they need an egg. Virgin births are a form of asexual reproduction as they do not require genetic information from sperm. It also reduces adverse genetic mutations, which are often associated with inbreeding (when close relatives mate). This diversity can be important if a species needs to adapt. In terms of evolution, sexually reproducing species are thought of as being more advanced, as their offspring are genetically diverse, with unique gene combinations from their parents. Sexual reproduction in species such as humans needs sperm to fertilise eggs and create an embryo. If the environment is bad for one member of a species, it is bad for all, and could lead to extinction. However, this produces lots of organisms that are genetically identical, and a lack of genetic variation means that individuals cannot adapt to changing conditions. Plants reproduce in a similar way, including splitting, budding and fragmenting. Our ancient ancestors were asexual and essentially made clones of themselves. Species can reproduce either sexually, combining genetic material from two parents, or asexually. Baby lizards, snakes, sharks and birds, including the California condor, have all been documented hatching from unfertilised eggs. This isn’t the first case of a virgin birth in the animal kingdom. But one contained a fully formed foetus, genetically identical to its mother, showing no evidence of input from any males. The eggs failed to hatch and the contents of six of them were indiscernible. She laid a clutch of 14 eggs, of which seven seemed viable and were artificially incubated. The first evidence of a virgin birth in crocodiles has been reported in a captive American crocodile, Crocodylus acutus, who was housed on her own for 16 years in a zoo in Costa Rica. But virgin births actually do happen in the natural world. Mars the ancient Roman god, Horus the ancient Egyptian god and Qi from ancient Chinese mythology were all born to virgins. Stories of virgin births, where young are produced without fertilisation, have been told throughout history. The following essay is reprinted with permission from The Conversation, an online publication covering the latest research.
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