Iguana

Iguana

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Encyclopedia
Iguana is a herbivorous genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

 native to tropical areas of Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

. The genus was first described in 1768 by Austrian naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...

 Josephus Nicolaus Laurenti
Josephus Nicolaus Laurenti
Josephus Nicolaus Laurenti was an Austrian naturalist of Italian origin.Laurenti is considered the auctor of the class Reptilia through his authorship of on the poisonous function of reptiles and amphibians...

 in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Two species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 are included in the genus Iguana: the Green Iguana
Green Iguana
The Green Iguana or Common Iguana is a large, arboreal herbivorous species of lizard of the genus Iguana native to Central and South America...

, which is widespread throughout its range and a popular pet, and the Lesser Antillean Iguana
Lesser Antillean Iguana
The Lesser Antillean Iguana is a large arboreal lizard endemic to the Lesser Antilles. It is one of two species of lizard of the genus Iguana and is in severe decline due to habitat destruction, feral predators, hunting, and hybridization with its sister species the Green iguana...

, which is endemic to the Lesser Antilles
Lesser Antilles
The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...

 and endangered due to habitat destruction.

The word "iguana" is derived from a Spanish form of the original Taino
Taíno people
The Taínos were pre-Columbian inhabitants of the Bahamas, Greater Antilles, and the northern Lesser Antilles. It is thought that the seafaring Taínos are relatives of the Arawak people of South America...

 name for the species "Iwana".

Anatomy and physiology


The two species of lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

 within the genus Iguana possess a dewlap
Dewlap
A dewlap is a longitudinal flap of skin that hangs beneath the lower jaw or neck of many vertebrates. While the term is usually used in this specific context, it can also be used to include other structures occurring in the same body area with a similar aspect, such as those caused by a double...

, a row of spines
Spine (zoology)
A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin...

 running down their back to their tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

, and a third "eye" on their head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

. This eye is known as the parietal eye
Parietal eye
A parietal eye, also known as a parietal organ or third-eye or pineal eye, is a part of the epithalamus present in some animal species...

, visible as a pale scale on the top of the head. Behind their neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 are small scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s which resemble spikes, known as tuberculate scales. These scales may be a variety of colors and are not always visible from close distances. They have a large round scale on their cheek known as a subtympanic shield.

Iguanas have excellent vision and can see shapes, shadows, colors and movement at long distances. Iguanas use their eyes to navigate through crowded forests, as well as for finding food. They use visual signals to communicate with other members of the same species.

The tympanum
Tympanum (zoology)
The tympanum is an external hearing structure in animals such as frogs, toads, insects, and mammals, to name a few.-Anurans:In frogs and toads, it is located just behind the eye. It does not actually process sound waves; it simply transmits them to the amphibian's inner ear, which is protected...

 is the iguana's ear drum, and is located above the subtympanic shield and behind the eye. Iguanas are often hard to spot, as they tend to blend into their surroundings. Their scale colors are a mode of hiding from larger predators.

Male iguanas, as well as other male members of the order Squamata
Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...

, have two hemipenes
Hemipenis
A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...

.

Species Status


The forested areas where iguanas live face increasing depletion. Trees felled for export and cleared for an expanding human population. Iguanas and other
reptiles are part of a multi-billion dollar international wildlife trade due to the increasing demand for odd or unusual plants, animal, and animal artifacts like skins.

Green iguanas are classified as "threatened" and are listed in Appendix II of the Convention of International Trade of Endangered Species (CITES). This means exporters and importers must have special permits to move the reptiles across international borders. Buying and owning iguanas is legal once they reach their destination. Other types of iguanid lizards like the Cyclura face extinction and are protected by more stringent import and export laws.