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Flora the Komodo dragon walks around her enclosure at Chester Zoo, Chester, England on Monday, Dec. 18. In an evolutionary twist, Flora has managed to become pregnant all on her own without any male help. Other reptile species reproduce asexually in a process known as parthenogenesis. But Flora's virginal conception, and that of another Komodo dragon earlier this year at the London Zoo, are the first time it has been documented in a Komodo dragon.

Komodo dragon
The Komodo dragon or Komodo Monitor (Varanus komodoensis) is the largest living species of lizard, growing to an average length of 2-3 metres (approximately 6.5-10 feet). It is a member of the monitor lizard family, Varanidae, and only inhabits the islands of Komodo, Rinca (or Rintja), Padar, Flores, Gili Motang, Owadi and Samiin in central Indonesia. [1]

Sightings of the Komodo dragon were first reported to Europeans in 1910. Widespread notoriety came after 1912, in which Peter Ouwens, the director of the Zoological Museum at Bogor, Java, published a paper on the topic. In 1980, Komodo National Park was founded to help protect its limited population.

Komodo dragons are carnivorous. Although they eat much carrion, studies show that they also hunt live prey with a stealthy approach followed by a sudden short charge, during which they can reach of up to 20 km/h (~13 mph). Komodo dragons have not traditionally been considered venomous, but it has recently been suggested that they may produce a weak venom (Fry et al., 2006). In addition to the possible venom, it also possesses virulent bacteria in its saliva of which more than 15 strains have been isolated. These bacteria cause septicemia in their victim; if an initial bite does not kill the prey animal and it escapes, it will commonly succumb within a week to the resulting infection. The lizard is able to locate its prey using its keen sense of smell, which can locate a dead or dying animal from a range of up to four miles. The Komodo dragon appears to be immune to its resident bacteria.

Feeding follows a social hierarchy - the dominant male eats first, with other dragons eating only when he is finished. Females however do not follow any set hierarchy and eat together. Komodo dragons eat by tearing large chunks of flesh while holding their food down with their forelegs then swallowing it whole. Their loosely articulated jaws and expandable stomachs allow them to eat up to 80 percent of their body weight in one meal, akin to a 200 lb man (90.7 kg) eating 160 lbs (72.6 kg) of food during one sitting.

The Komodo dragon diet is wide-ranging, and includes invertebrates, other reptiles (including smaller dragons), birds, bird eggs, small mammals, monkeys, wild pigs, goats, deer, horses and water buffalos. Occasionally they have been known to consume humans and human corpses. Over a dozen human deaths have been attributed to dragon bites in the last century, although there are reports of survivors of the resulting septicemia.

Conservation status
There are approximately 6,000 living Komodo dragons

Reproduction
Mating occurs between May and August, with the eggs laid in September. During this period, males fight over females and territory by grappling with one another upon their hind legs, with the loser eventually being pinned to the ground. During copulation, the male often scratches the female's back, sometimes even to the point of drawing blood. The female will lay her eggs in the ground or in tree hollows (thereby lending them a certain degree of protection). Clutches contain an average of 20 eggs which have an incubation period of 7 months. The hatchlings are born more or less defenseless, and many do not survive. Young Komodo dragons spend much of their first few years in trees, where they are relatively safe from predators. Dragons take about three to five years to mature, and may live for up to 30 years.

There are recorded examples of parthenogenesis (reproduction without the contribution of a male), a phenomenon also known to occur in some other reptile species.

On December 20, 2006, it was reported that Flora, a captive Komodo dragon living in the Chester Zoo in England, is the second Komodo dragon to have fertilized her eggs herself, via the process of parthenogenesis. Scientists at Liverpool University in northern England verified that Flora had had no male help by means of genetic tests on three eggs that collapsed after being moved to an incubator. (Flora had never had physical contact with a male dragon.) Sungai, a Komodo dragon at London Zoo, laid a clutch of eggs in early 2006 after being separated from males for more than two years. Scientists initially assumed that she had been able to store sperm from her earlier encounter with a male (an adaptation referred to as superfecundation), but after being apprised of the condition of Flora's eggs, testing showed that Sungai's eggs were also produced without outside fertilisation.[8]

Due to a ZW chromosomal sex-determination system, all progeny of Komodo dragon parthenogenesis are male. When a female Komodo dragon(who has ZW sex chromosomes) reproduces in this manner, she provides her progeny with only one chromosome from each of her pairs of chromosomes, including only one of her two sex chromosomes. This single set of chromosomes is duplicated in the egg, which develops parthenogenetically. Eggs receiving a Z chromosome become ZZ (male) while those receiving a W chromosome become WW and fail to develop. [9]

It has been hypothesised that this reproductive adaptation allows a single female to enter an isolated ecologic niche (such as an island) and by parthenogenesis produce male offspring, thereby establishing a sexually reproducing population. (It permits mating of the mother with her male progeny to produce both male and female offspring).

Parthenogenesis
From Wikipedia, the free encyclopedia

Parthenogenesis (from the Greek παρθενος parthenos, "virgin", + γενεσις genesis, "birth") describes the growth and development of an embryo or seed without fertilization by a male. Parthenogenesis occurs naturally in some species, including lower plants (called agamospermy), invertebrates (e.g. water fleas, aphids, some bees and parasitic wasps), and vertebrates (e.g. some reptiles,[1] fish, and, very rarely, birds[2]).

The offspring of parthenogenesis will be all female if two like chromosomes determine the female sex (such as systems where XX is female and XY is male), but male if the female sex is determined by unlike chromosomes (such as systems where WZ is female and ZZ is male), because the process involves the inheritance and subsequent duplication of only a single sex chromosome. The offspring may be capable of sexual reproduction, if this mode exists in the species. A parthenogenetic offspring is sometimes called a parthenogen. As with all types of asexual reproduction, there are both costs (reduced genetic diversity generated) and benefits (reproduction without the need for a male) associated with parthenogenesis.

Parthenogenesis is distinct from artificial animal cloning, a process where the new organism is identical to the cell donor. Parthenogenesis is truly a reproductive process which creates a new individual or individuals from the naturally varied genetic material contained in the eggs of the mother. A litter of animals resulting from parthenogenesis may contain all genetically unique siblings without any twins or multiple numbers from the same genetic material. Parthenogenic offspring of a parthenogen are, however, all genetically identical to each other and to the mother, as a parthenogen is homozygous.

In April 2004, scientists at Tokyo University of Agriculture used parthenogenesis to successfully create fatherless mice. In theory, the process could be used to reproduce humans after extensive testing and perfection. The alternation between parthenogenesis and sexual reproduction is called heterogamy. Forms of reproduction related to parthenogenesis but that require the presence of sperm are known as gynogenesis and hybridogenesis.