As an endemic species found only in Indonesia, have you ever ever wondered how Komodo dragons managed to survive to today?
In fact, the survival of the Komodo dragon is exclusive. They are in a position to breed even when there are not any males within the population. This phenomenon is feasible because female Komodo dragons can provide birth to offspring without the necessity for fertilization by a male.
This phenomenon is generally known as parthenogenesisa singular reproductive process that permits female Komodo dragons to father offspring without the involvement of a male.
The term parthenogenesis, derived from Greek and meaning “virgin birth”, was first utilized by the Swiss naturalist Charles Bonnet within the mid-18th century. Initially, it was thought that this process only applies to plants, insects and other invertebrates, where parthenogenesis is a comparatively common phenomenon.
However, recent biological research has shown that similar processes occur in fish, reptiles, birds and even mammals.
Parthenogenesis offers some unusual mechanisms on this planet of reproduction. For some species, it’s an emergency alternative when it’s difficult to seek out a mate; for others it becomes the one solution to proceed the road; and for still others it’s used flexibly depending on their ecological needs.
In the case of the Komodo dragon, the power to breed each sexually and thru parthenogenesis is assumed to have evolved in response to its isolated habitat within the Indonesian archipelago. Similar phenomena have been observed in other species, akin to dragonflies within the Azores, which engage in parthenogenesis when faced with a limited variety of partners.
Scientists speculate that this adaptation may allow female Komodo dragons to ascertain recent populations when left alone on a distant island, akin to after being carried away by a robust storm.
Read also: Why do Komodo dragons only exist in Indonesia?
In addition to their ability to put eggs without the assistance of a male, Komodo dragons even have a really unique sex determination system. Unlike mammals, where females have XX chromosomes and males have XY chromosomes, Komodo dragons follow the alternative principle. Their sex chromosomes are marked W and Z, with the ZZ combination producing males and the WZ combination producing females.
In female Komodo dragons, each egg comprises a W or Z sex chromosome. During parthenogenesis, the resulting embryo could have WW or ZZ chromosomes. Eggs with the WW combination cannot survive and can die, very similar to the YY combination in humans. However, embryos with the ZZ combination can survive, meaning that every one offspring resulting from parthenogenesis are male.
What’s unique about this process is the duplication of genes in the course of the creation of an egg (oogenesis), during which a small cell called the polar body – normally a replica of the egg’s DNA – shrinks and disappears. However, in Komodo dragons, this polar body acts like a sperm, fusing with an egg and producing an embryo.
Read also: Iron-coated teeth of Komodo dragons: a contemporary T. rex
In 2006, two zoos within the UK were surprised when female Komodo dragons gave birth without contact with a male. One even demonstrated the power to enter sexual reproduction mode after mating with a male.
This revealed the extraordinary flexibility of the world’s largest reptiles, in a position to adapt their reproductive methods – each sexual and asexual – to their needs.
“Parthenogenesis has never been recorded in Komodo dragons, so this is actually a world first,” said Kevin Buley, a researcher at Chester Zoo. In many zoos, female Komodo dragons often live in isolation from other individuals, and this adaptation allows them to proceed breeding even in confined conditions.
This unique adaptation plays a key role for the Komodo dragon population, which lives in an isolated environment where finding a mate is usually a challenge. Whether through mating or parthenogenesis, females can lay about 20 eggs in a single reproductive cycle.
This reproductive strategy could function a brief lifeline for the Komodo dragon, a critically endangered species with only about 1,000 adults left within the wild. In critical situations, the power to breed and not using a male might help maintain the population.
However, this strategy has vital limitations: on account of the unique nature of chromosomes, parthenogenesis produces only male offspring, which cannot proceed the asexual reproductive cycle into the following generation.
In the long term, this approach could cause health problems on account of inbreeding. As within the tragic story of Oedipus, low genetic diversity in a colony can weaken the species’ ability to face up to environmental challenges and disease, limiting the effectiveness of this strategy as a long-term solution to sustainability.
