The Lake Eyre dragon lizard or Salt-Lake Ground-dragon (Ctenophorus maculosus) mainly inhabits the edges of salt lake in South Australia for which it is named. It survives in this harsh habitat through adaptive mechanisms to tolerate high temperatures and lack of free water. The female C. maculosus possesses unique male rejection techniques which are currently the focus of further research.

Description

C. maculosus can be identified by a white to pale grey dorsal surface with black blotches and a white ventral surface with a dark longitudinal dark streak. Black and brown spots are observed throughout its body. This cryptic coloration allows the species to blend into the salt surface it inhabits, and color variations are found depending on the specific population’s environment. The adult male is about 11.5 centimeters long and the adult female is slightly shorter at 10.0 centimeters. C. maculosus possesses small, sunken eyes protected by serrated eyelids and eye linings. Its nostrils are connected to its nasal cavity by only a narrow downward slit. This nasal structure is adaptive for preventing nasal blockage from burrowing in sand. Other sand-burrowing American lizards have also developed similar nasal structures via convergent evolution

Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

, including species in the genera Ura

Uracentron

Uracentron is a genus of Tropidurid lizards. It contains only two described species at present.Genus Uracentron*Uracentron azureum*Uracentron flaviceps...

, Holbrookia

Holbrookia

Holbrookia is a genus of earless lizards, known commonly as the lesser earless lizards, which contains three recognized species that are found throughout the southwestern and central United States, and northern Mexico. They are characterized by having no external ear openings, presumably to prevent...

, and Phrynosoma

Horned lizard

Horned lizards are a genus of lizards which are the type genus of the family Phrynosomatidae. The horned lizard is popularly called a "horned toad", "horny toad", or "horned frog", but it is neither a toad nor a frog. The popular names come from the lizard's rounded body and blunt snout, which...

.

Distribution and Habitat

C. maculosus is endemic to the three largest dry salt lakes of inner South Australia (Lake Eyre

Lake Eyre

Lake Eyre is the lowest point in Australia, at approximately below sea level, and, on the rare occasions that it fills, it is the largest lake in Australia and 18th largest in the world...

, Lake Callabonna

Lake Callabonna

Lake Callabonna is a dry salt lake with little to no vegetation in northeastern South Australia, approximately southwest of the junction of South Australia, Queensland and New South Wales at Cameron Corner. It is an important site for late Pleistocene fossils...

, and Lake Torrens

Lake Torrens

Lake Torrens is a salt lake in central South Australia. It is located in the Lake Torrens National Park....

), with the densest population found in Lake Eyre. Three habitat characteristics characterize its distribution: a surface crust, a thick layer of dry sand or clay under the crust, and a constant source of humidity. This dragon lizard inhabits the edges of the lakes where it burrows in the damp sediments under the salt crust.

Diet

The main food source for C. maculosus is the harvest ant Melophorus. The nest-mounds of these ants provide an additional benefit to the dragon lizard as lookout points, basking sites, and sources of shade. C. maculosus is an opportunistic feeder and also feeds on other insects trapped on the salt surface.

Adaptations to Harsh Environment

C. maculosus has developed behavioral mechanisms of avoiding environmental stresses in a similar fashion to desert-adapted animals. It uses various postures and movements to maintain an optimal body temperature. Its physiology has also adapted to the lack of free water by having a low evaporation rate, thus reducing water loss from the body.

Flooding Response

When C. maculosus is forced to the beach surface by flooding, it changes color to a deeper grey with more numerous black and brown spots to match the pebbly beach sands. It also appears to show greater muscle coordination and the body inflates, which helps the dragon lizard float on the surface of the water.

Sexual Behavior

The male C. maculosus is highly aggressive and attempts to force copulation with females by repeated harassment. Male harassment behavior can include chasing, biting, and pinning the female to the ground. On occasion, the male may injure or kill the female it is attempting to copulate with by its mating grasp. The female employs three main rejection strategies to protect herself: fleeing from the male, performing a threat display, or flipping over on her back to prevent copulation. This last behavior is unique to C. maculosus and one species of insect. The female develops a bright orange color on its throat when it is reproductively receptive. In threat display and flipping-over rejection, the female reveals its throat to communicate rejection to the male. Oviposition

Oviposition

Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....

results in significant declines in steroid levels, a fading of color from the throat, and an increase in rejection behavior.

External Links

• IUCN Ctenophorus maculosus
• ReptilesDownUnder.com