Water Dragon

Reviewed by: BD Editors

The water dragon is a species well adapted to the water as a defense mechanism.
A Water Dragon

Kingdom Animalia
Phylum Chordata
Class Reptilia
Order Squamata
Family Agamidae
Genus Physignathus + Intellagama
Species Physignathus cocincinus (Chinese) + Intellagama lesueurii (Australian)
Niche Forest-Dwelling Insectivore
Length Up to 3.3 ft (1 m)
Weight Up to 2.2 lbs (1 kg)
Lifespan 10-15 years
Social Structure Small, hierarchical groups
Conservation Status Vulnerable
Preferred Habitat Tropical Rain Forests, near water
Average Clutch Size Around 7 eggs
Main Prey Species Insects, though some vegetation is also eaten
Predators Large birds, mammals, other reptiles, humans

The Basics

The water dragon is a type of lizard native to Southeast Asia, Australia, and New Guinea. They are known for having a crest on their neck and a well-developed ability to swim and hold their breath. In fact, the main defense of the water dragon is to drop from the trees into a river or lake. Here, they can remain hidden underwater for up to 90 minutes!

While the water dragon is commonly kept as a pet, the species is considered “Vulnerable” in the wild – in part due to the pet trade. Plus, while the pet trade has depleted the water dragon from its natural environment, it has also established invasive populations in other areas. So, keeping a water dragon as a pet is questionable, at best. However, captive breeding operations may help reduce the harvest of water dragons from the wild.

Australian Water Dragons have much darker coloration than their Chinese counterparts.
An Australian Water Dragon

In their natural environment, water dragons are very interesting lizards. Related to other “dragon” species in the subfamily Amphibolurinae, the water dragon consists of two main species: the Australian water dragon and the Chinese water dragon. The Australian water dragon is a grayish-brown color and often has a black stripe on its eye. By comparison, the Chinese water dragon is a greenish color that does not have a stripe on its eye. Both species have a frilled crest just behind their rather large head.

Water dragons are insectivores, feeding on a wide variety of insects found in tropical and subtropical environments. When they are not hunting insects, the water dragon spends its time basking in the trees. Water dragons tend to form hierarchical social groups, with the biggest males and females getting the best basking spots and mating opportunities.

Interesting Insights from the Water Dragon!

While the water dragon has a mythical name, it is actually a perfect species to explain several different biological concepts that are very real.

Pineal Eye

Like most reptiles, water dragons have an organ known as the pineal eye. Between their eyes lies a small, iridescent patch of scales that cover light-receiving nerve endings. Many lizards use this organ to sense the intensity of sunlight, which helps them determine which spots are the best places to bask. Basking is necessary for lizards because it raises their body temperature, allowing them to keep their temperature in a specific range. What’s more interesting is that humans (and all mammals) have a similar structure – the pineal gland.

The water dragon uses its pineal eye to detect the best basking spots.
Water Dragons use their pineal eye to find good basking spots

Though the human pineal gland is buried deep within our brains, it is connected to neurons in the eye. When our eyes perceive light, a signal is sent to the pineal gland. This signal causes the pineal gland to stop producing melatonin, a hormone crucial to our sleep and wake cycles. When no or very little light is detected by the pineal gland, it again starts to release melatonin. This hormone affects many parts of your brain and body – preparing you for sleep! This helps regulate our circadian rhythm and keeps our bodies healthy.

Parthenogenesis

Parthenogenesis is an ability that some animals have to reproduce asexually, even though the species is normally sexually reproducing. Through parthenogenesis, a female is able to create viable offspring – without ever having been fertilized by a male. Essentially, this is equivalent to a virgin birth!

The water dragon is one of only a few species that has been observed completing parthenogenesis. Through this process, an unfertilized egg goes through a duplication event to become a diploid cell. If the female’s genetics do not contain a large number of deleterious recessive mutations, the offspring can be viable. Studies on water dragons have shown that parthenogenesis does occur, and genetic analysis showed that these offspring were almost identical to the female they came from.

The Chinese water dragon has a much more green coloration and is slightly smaller than the Australian water dragon.
A Chinese Water Dragon

Interestingly, parthenogenesis is seen in a number of other reptiles including garter snakes, Colombian rainbow boas, and common boas. However, it is much more common in invertebrates like insects, snails, worms, and microscopic organisms. Still, parthenogenesis has been seen in birds, sharks, and other groups – though it is usually limited to a single species and is incredibly rare.

Cite This Article

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Biologydictionary.net Editors. “Water Dragon.” Biology Dictionary, Biologydictionary.net, 19 Jul. 2020, https://biologydictionary.net/water-dragon/.
Biologydictionary.net Editors. (2020, July 19). Water Dragon. Retrieved from https://biologydictionary.net/water-dragon/
Biologydictionary.net Editors. “Water Dragon.” Biology Dictionary. Biologydictionary.net, July 19, 2020. https://biologydictionary.net/water-dragon/.

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