Virgin Birth on Way for Komodo Dragon
One of Two Such Cases Known for Animal
By MARIA CHENG
AP
CHESTER, England (Jan. 19) – In an evolutionary twist, Flora the Komodo dragon has managed to become pregnant all on her own without any male help. She is carrying seven baby Komodo dragons.
“We were blown away when we realized what she’d done,” said Kevin Buley, a reptile expert at Flora’s home at the Chester Zoo in this town in northern England. “But we certainly won’t be naming any of the hatchlings Jesus.”
Other reptile species reproduce asexually in a process known as parthenogenesis. But Flora’s virginal conception is the second documented in a Komodo dragon. The first was earlier this year at the London Zoo.
The reptiles, renowned for their intelligence, are native to Indonesia. They are the world’s largest lizards and have no natural predators – making them on par with sharks and lions at the pinnacle of the animal kingdom.
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How is this possible?
nature find a way!!!
How parthenogenesis evolves is still unclear, but natural hybridization is often involved (when a male and a female from different but closely related species reproduce). The genetic material of the offspring comes from the mother, but is typically not identical because most species have pairwise chromosomes, and eggs can thus have a different combination of chromosomes for each of these pairs (e.g. if the mother has chromosomes AB, then every egg will have AA, AB or BB). In some species such as Komodo dragons, the offspring inherits only one chromosome per pair, which is doubled (i.e. AB is impossible.) In other species, gene splicing can also “mix things up” to an extent by forming a chromosome that contains some genes from A and some from B.
Male Komodo dragons, unlike men, have two identical sex chromosomes (called ZZ), whereas females have two different ones (called WZ). Parthenogenic offspring of a KD female will thus all be ZZ (male) or WW. The latter is a non-viable combination of sex chromosomes – these eggs are formed but die off. So parthenogenic offspring in KDs is all male and parthenogenic reproduction for more than one generation is not possible (although the males can still reproduce sexually). Some scientists believe that parthenogenesis is quite common in KDs, and this would help explain why male dragons outnumber females 3:1.
In other species, females have two identical sex chromosomes, or mixed chromosome pairs are possible, and so at least some parthenogenic offspring can itself reproduce asexually. In some even rarer species, all females reproduce this way and there are no males at all. Since there is no genetic exchange, the genetic pool grows very small and the descendants will be genetically very similar to their mothers, just like clones. Interestingly, in some lizard species with only parthenogenic reproduction the females will imitate male mating rituals (which are known from closely related, sexual species) with other females. The one playing the female role is not fertile otherwise, or markedly less fertile. Still, no genetic material is exchanged.
New parthenogenic species should be assumed to form constantly while others go extinct. The fact that parthenogenesis (at least pure parthenogenesis) is so rare is testament for the long term benefits that sexual reproduction has for a species’ genetic diversity. (See Wikipedia for a great amount of detail.)