Indonesian dragons can breed without the benefit of male camaraderie . Last week, the researchers reported in Nature that the only two sexually mature female Komodo dragons in Europe from the viable eggs without insemination of a male. A Komodo , named Flora , lives at the Chester Zoo in England and has never loved a man , but a few months ago, she laid a clutch of 11 eggs , which develop eight appear normal and may come as soon as January. Earlier this year , a now deceased woman named Sungai from the London Zoo laid a clutch of 22 eggs , four of which yielded normal male dragons - even though Sungai had not had a date in two and a half years .Some reptiles can hold sperm for several years , so at first the researchers believe Sungai eggs had a father. But genetic analysis ruled out , unless the father were somehow genetically identical to her . ( Sungai did later mate with a male and laid a normally fertilized clutch , so do not think she died a virgin . )
These " virgin births " raised eyebrows because this asexual method of reproduction, called parthenogenesis , is rare in vertebrates : only about 70 vertebrate species can do (that's about 0.1 percent of all vertebrates ) . Biologists have known that some lizards can engage in parthenogenesis , but sees it among Komodo dragons surprised zookeepers .
Despite the fact that only a mother , the offspring are no clones. That is because an unfertilized egg has only half of the genes of the mother. The sperm is supposed to provide the other half . In parthenogenesis , maternal half - double set of chromosomes to generate the full complement . Hence, the offspring derives all the genes of the mother , but they are not identical to its genome .
Komodos have a curious twist in their sex determination as well. Although we think of XX females ( ie , with two X chromosomes ) and males XY , it's the other way around in this giant monitor lizards . Two identical sex chromosomes make a male Komodo , and two different ones make a female. Biologists label sex chromosomes , the Komodo 's as W and Z , so ZZ makes a male and WZ makes a female. Birds, some insects and a few other lizard species also rely on these sex - determination system . (Embryos of some reptiles - especially crocodiles and turtles - Do not have sex chromosomes , but rather the incubation temperature dictates their gender. )
In Komodo women , each egg contains either a W or Z Parthenogenesis hence leads to embryos that are either WW or ZZ . Eggs that consist of WW material are not viable and die off (just as YY is not a viable combination ) , in contrast , ZZ works . So all Komodo boy and will male ( ZZ ) are .
Apparently , in these Komodos the doubling of the egg genes occurred essentially an egg , sperm instead worked fertilization . Oogenesis , the biological process of making an egg , typically also results in a polar body - a mini egg of species, which are a duplicate DNA egg . Normally this polar body shrivels and disappears . In Komodos however polar bodies evidently acted converted into embryos. As sperm and ova
The ability to both sexual and parthenogenetic reproduction probably due to isolated natural habitat of the Komodo dragon , live and on islands in the Indonesian archipelago . Researchers have seen other species resort to parthenogenesis in isolation , such as damselflies in the Azores . The ability , researchers speculate , the dragons have enabled to establish and females had found themselves stranded alone on neighboring shores , as might happen during a storm new colonies.
High school biology texts tend to gloss over parthenogenesis , usually indicating the process as rare and limited to mostly small invertebrates . But the phenomenon has emerged from the backwaters in recent years , mainly as a tool for science. Some scientists hope to use to get around . Ethical issues surrounding embryonic stem the phenomenon They can share puncture crazy , so the penetration of sperm simulate . An unfertilized human egg Continue to divide in the blastocyst stage of 50 to 100 cells such cheated eggs before petering out naturally .
In principle, it may be possible to keep cell division. In 2004 , as a means to the details of how fertilized eggs develop clarify , scientists in Japan engaged in a number of genetic tricks to create a fatherless mouse . Such a development is unlikely to happen in the little town of Bethlehem two millennia ago - the mistranslation of " young girl or a girl " in " virgin" , explains the story a lot better . But if the Komodo dragons ' amazing performance parthenogenesis shows , nature has a lot to learn about making do without a mate.
