IGUANA: CHARACTERISTICS, SPECIES, HABITAT, REPRODUCTION - BIOLOGY - 2025

Iguana is a genus of reptiles that is part of the Iguanidae family. Animals belonging to this clade have a dorsal crest, made up of keratinized scales shaped like a beak. This extends from the occipital region to the tail.

In addition, they have a gular sac. The male extends it to court the female or to demonstrate superiority to other males. Likewise, it contributes to the regulation of body temperature.

Iguana iguana. Source: Cayambe

The iguana has a "third eye" on the top of its head, which is associated with the pineal gland. This is not capable of forming images, it works as a photoreceptor unit for light and movement.

Its natural habitat is the tropical jungles and forests of South America, Central America and the Caribbean. There she is in the treetops, where she spends most of her time foraging and resting.

This genus is made up of two species, the green iguana (Iguana iguana) and the Caribbean iguana (Iguana delicatissima).

The distinction between these can be based on the fact that the green iguana has black stripes on its tail. In addition, under the eardrum it has some pearly scales. These aspects are absent in the other species.

Danger of extinction

Iguana populations have been progressively decreasing in recent decades. The Iguana iguana species belongs to the list of species that make up Appendix II of CITES. In this way it is protected and under the legal control of its import and export.

Thus, although the green iguana is not within the group of animals with a high probability of becoming extinct, it is possible that it is, if its commercialization is not controlled.

For international trade, the CITES legal framework does not provide a specific import permit. However, each country could have legal statutes that regulate this. The purpose is that the iguana trade does not harm its conservation within the natural habitat where it is found.

On the other hand, the Iguana delicatissima is part of the IUCN Red List, being considered a reptile vulnerable to extinction.

Threats

One of the causes that has caused the population decline of this genus is the consumption of products obtained from iguanas. Eggs and meat are an important source of protein in many communities, although they are also valued for their alleged aphrodisiac and medicinal properties.

In addition, fine articles for personal use, such as shoes and handbags, are made with the skin, which are sold at exorbitant prices.

Likewise, its sale as a pet has also influenced the vulnerability of both species. Although the majority of these animals could come from farming farms, it is highly likely that wild iguanas will be caught to supplement commercial requirements.

In particular, the Caribbean iguana (Iguana delicatissima) is affected by the fragmentation of its habitat, because it is cut down and deforested for the establishment of agricultural and urban spaces.

Furthermore, the introduction of the green iguana as an exotic species in the Lesser Antilles has affected its development on that Caribbean island. This has generated fierce competition for resources and food, generating decline in at least three islands: Islas de los Santos, San Bartolomé and the Isla de la Tierra Baja.

characteristics

2004 by M. Betley. Wikimedia Commons

Size

The iguana can be between 1.5 and 1.8 meters long, including the tail. However, species up to 2 meters long have been found. Regarding the weight, it oscillates around 15 and 17 kilograms.

The senses

Eyes

The orbit of the eyes measures, in adults, about 1.5 centimeters in diameter and 1 centimeter in height. The eyelids are thin, the upper one has less mobility than the lower one, which is raised to close the eyeball.

The species of this genus have, in the central and upper region of the head, in the parietal bones, a transparent scale. This is known as the pineal eye or third eye.

Actually, it is a photoreceptor that is connected to the pineal gland, through a parietal nerve, which originates in the retina. Although it has a retina and a lens, it does not function the same as a normal eye. This is because the retina is primitive and the lens is not capable of forming images.

This structure is sensitive to light and can detect movements. In this way, it works as a compass, calibrated with sunlight. Thus, you can guide the iguana in a fairly precise way, as it moves through its habitat.

In addition, it is also used as a defense organ, since it could confuse predators, causing them to approach from above.

Ear

The iguana lacks an external flag. In the case of this reptile, it has a distinct transparent scale, located close to the eyes. It covers a short canal, which contains a tympanic membrane.

Smell

These animals detect pheromones using the vomeronasal organ, also known as the Jacobson's organ. This accessory structure is molecularly and structurally different from the primary olfactory epithelium.

Said chemoreceptor organ is innervated by fibers from the secondary olfactory bulb. It is lodged in the palate, forming two pits, covered by a sensory epithelium.

In iguanas, the tongue is responsible for capturing odor particles and leading them to the chambers of the vomeronasal organ.

Respiratory system

Nostrils

The nostrils are oval in shape and are made up of bone, skin, and cartilage, which fill the contour. In this, the nasal glands stand out, which have the function of eliminating excess salt. That is why occasionally this animal may sneeze and expel a whitish powder, which is sodium chloride.

Larynx

This organ connects the lower part of the pharynx with the trachea. It is tubular in shape and is made up of two cartilages, one circular and the other epiglottic. These move thanks to the laryngeal muscles.

Windpipe

It is an elastic and membranous tube that is located after the larynx, where it divides into two bronchi. It has between 47 and 60 cartilaginous rings.

Lungs

The green iguana has a pair of lungs, elongated in shape. In young people, the lung tissue reaches up to approximately half of the pleural sac, the rest is formed by the pleura.

One aspect that characterizes these animals is that they do not have a diaphragm. Due to this, the main responsible for respiratory movements is the intercostal muscles.

Skin

The iguana's skin has two layers, the epidermis (external) and the dermis (internal). In the epidermis there are blood vessels and nerves that nourish the dermis. In addition, it is made up of keratinous scales. Each one is attached to the other through a flexible area, which allows the body to bend and move freely.

This animal regularly sheds its fur. This occurs because a new dermal integument is formed, under the old one. When this process is complete, the old layer comes off.

All members of this species have spike-shaped dorsal ridges, which arise in the occipital region and extend to the tail. In addition, they have a gular sac, located below the throat. In this fold there are also some ridges, which vary in number depending on the stage of development.

In relation to the Iguana iguana species, in newborns, the crest is poorly developed. In the juvenile stage, it has around 210 dorsal ridges and in adults it can have up to 358.

Coloration

These reptiles have a coloration that ranges from gray to green, in light and dark tones. Some species have dark stripes on the tail, where they form a kind of rings.

These colors may vary for various reasons, such as adaptation to changes in temperature, in the heat period and as an expression of stress or illness.

Likewise, the colors of his skin give him the perfect camouflage to hide among the foliage of the trees where he lives.

Femoral pores

Within the glands found in the skin are the femoral pores, located in a row over the ventral area of ​​the thighs. Males have these larger structures than females.

In the heat period, the pores increase in size and become more noticeable. These secrete a chemical substance with a very particular smell, which is used by the male to attract the female and to mark the territory.

Taxonomy and species

• Animal Kingdom.
• Subkingdom Bilateria.
• Chordate Phylum.
• Vertebrate Subfilum.
• Tetrapoda superclass.
• Class Reptilia.
• Order Squamata.
• Suborder Iguania.

Family Iguanidae

Genus Iguana (Laurenti, 1768)

Species

This genus is divided into two species:

Iguana delicatissima or Caribbean

© Hans Hillewaert Wikimedia Commons

This species is native to the Lesser Antilles. The coloration of this reptile can vary between the diverse populations of the island. However, the predominant color is gray, with green spots in the lower region. On the head it has large scales, of an ivory tone.

In males, the gular sac is pink and around the eyes has blue scales. These are larger than the females, thus, their body measures approximately 40 centimeters and the tail 80 centimeters.

Iguana iguana or green

Christian Mehlführer, User: Chmehl

The green iguana is a large herbivorous species native to South and Central America. This species could reach a length of 2 meters, including the tail. The weight can be around 10 kilograms.

In terms of coloration, newborns can be bright green or a little more brown, especially those that live in xerophilic regions. Also, they have an aquamarine stripe on the front limbs and dark eyelids.

The young ones are light green and the adults dark green. These may turn orange during the reproductive period. The gular sac is green and there are black bands on the tail.

Habitat and distribution

Brieg

Iguanas are distributed in the humid jungle regions of South America, Central America, North America and the Caribbean.

The Iguana iguana species spans a vast geographic area. Thus, specimens can be found from the southern part of Brazil and Paraguay to the Caribbean islands and the northern part of Mexico.

In the United States, it is an exotic species found in wild populations in Hawaii, Florida, and in Texas, in the Rio Grande Valley.

The Caribbean islands where he lives are Cozumel, Roatán, Utila, Corn islands, Guanaja, San Andrés, Providencia, Trinidad, Aruba, Tobago and other islands of the Lesser Antilles.

Likewise, the Iguana iguana has been introduced in Barbuda, Antigua, British Virgin Islands, Bahamas, Barbuda. It is also found in the Virgin Islands, Cayman Islands, Canary Islands, Fiji, Martinique, Puerto Rico, and on the island of Saint Martin.

The Iguana delicatissima is endemic to the Lesser Antilles, where it inhabits thickets, mangroves and forests in Saint Martin, Anguilla, Saint Eustatius, Guadeloupe, Antigua, Martinique and Dominica.

Habitat

The iguana is an arboreal animal, which descends to the ground mainly to nest. Thus, it spends most of its time in the upper part of the trees, in those regions of thick vegetation.

An example of these ecosystems are the humid tropical forests, mangroves, grasslands, forests and river banks, which do not exceed 1000 meters above sea level. In these, the annual temperature is between 27 and 28 ° C, with a humidity higher than 70%.

Also, it could live in other habitats, such as dry forest, savannas, gallery forests, it could even live on xeric islands, with shrub-like vegetation.

Like reptiles, they are cold-blooded animals. This leads the iguana to climb to the highest branches to receive the sun's rays and warm its body. After this, it is dedicated to looking for its food, made up of leaves, shoots and fruits, which it obtains without having to go down to earth.

Reproduction

Female reproductive system

Ovaries

These are two and they are located in the abdominal cavity. Each contains a series of follicles, developed to different degrees, covered by a thin mesovarium.

Oviduct

The iguana has two oviducts, characterized by having an irregular internal surface and by having a developed infundibulum. Each of these empties independently into the cloaca.

Male reproductive system

Hemipenis

It is a bi-lobed penis that the iguana can keep it, inverted and voluntarily, inside the cloaca. It has an elongated shape and is structured with erectile muscle tissue. This reproductive organ is located in the ventral area of ​​the base of the tail.

Spermatic Cord

This organ is located in the abdominal cavity, at the level of the lumbar vertebrae. Its function is to transport the sperm produced by the testicles.

Reproductive changes

In the male, the onset of sexual maturity is accompanied by a series of physical and behavioral changes. This these are:

-Increase in the size of the sub tympanic scales.

-Increased size of the dorsal crest, particularly at the level of the neck.

-The femoral pores are more noticeable, because they are enlarged.

-The hemipenes can be seen, as two lumps in the cloaca region

-In the Iguana iguana species, the male's skin acquires an orange coloration.

-They could become irritable or aggressive, leading to the adoption of threatening postures in adverse situations.

-Loss of appetite.

In females, a number of physical and behavioral variations also occur. Some of these are:

-The Iguana iguana species could vary the color of the belly and legs, turning orange.

-Loss of appetite, which could cause a notable decrease in body weight.

-Nervousness.

-They often try to excavate, to open tunnels where they could place the eggs, if they have them.

Reproductive cycle

Females may be courted for up to four weeks before they are ready to mate. During courtship, the male frequently shakes his head up and down, extends the gular sac and contracts the abdomen, thus maintaining an upright position.

Once the female accepts the male, copulation behavior begins. In this, the male approaches the female from behind, making various movements with her head. The female then moves her tail to the side, arching it a little.

Next, the male mounts on the female and holds her, biting her in the neck area. This folds the tail under the female and inserts a hemipenis.

Once the female has been fertilized, she leaves the area. Egg laying occurs 8-10 weeks after copulation. The nest is usually a hole over a meter deep, which was dug into the ground by the female

In this it lays around 25 and 30 eggs. After laying them, he buries them. Thus, with the heat of the solar rays, the eggs are incubated for approximately 2 or 3 months.

Feeding

Andrzej Barabasz (Chepry)

The iguana is herbivorous and polyspecific, since it consumes a great diversity of plants. From this, take the buds, leaves, fruits and flowers. However, the leaves are the main food of this reptile.

In the early stages of life, the young may consume some insects. Once adult, their food is exclusively of plant origin.

Some of the favorite species are Ipomoea sp., Abutilon sp., And Tabebuia rosea. As for the flowers, there are those of the Mexican Sabal, Gliricidia sepium, Tabebuia rosea and Rhizophora mangle. The fruits are consumed to a lesser extent, being the species Hamelia sp. the favorite for the reptile.

Digestive system

The oral cavity is wide. Its posterior part can be constricted, in order to occlude the nasopharynx and allow the animal to breathe, while its mouth is full of water.

The tongue is sharp. This organ fulfills several important functions, one of them is to facilitate the swallowing of food. Also, it can be used to take its food with it.

The teeth are serrated and of the same size. In addition, they are partially fixed in the bone. There are 7 orifices in the pharynx: two pairs, the choanas and the pharyngeal orifices that correspond to the nostrils, and three odd ones, the entrances to the pharynx, larynx and esophagus.

The food bolus continues its transit through the esophagus and reaches the stomach. This organ is a very resistant membranous muscle, which fulfills a chemical and mechanical function. Later it reaches the intestines, thin and large, until it reaches the cloaca.

It has, internally, three divisions. These are, the coprodeo, where the feces are collected, the urodeo, where the substances that come from the genital and urinary systems are received and the proctodeo, a common chamber that communicates with the exit orifice.

Behavior

Kati fleming

Iguanas are diurnal and arboreal animals that like to stay near rivers or streams. Likewise, this reptile likes to swim. In doing so, it remains submerged with all four limbs hanging down. Its propulsion is carried out with the strong and powerful blows it makes with the tail.

Another behavior present in the iguana is the use it makes of its tongue. Often when they move, they do so with their tongues sticking out, touching some surfaces in their path. Even if he bumps into a female, an adult could touch her with this organ of the digestive system.

A possible explanation for this behavior, apart from allowing it to explore the environment, is that the reptile needs some microorganisms to facilitate its digestion. So, this is probably one way to get them.

The activities you do most frequently are eating and resting. The latter is of utmost importance, since it contributes to the regulation of the internal temperature of the body. When it is ready to rest, it does so on a branch and assumes two positions.

In one of these, the iguana keeps its head raised and, with the help of its front limbs, it maintains an upright position. Another position is to put both hind legs back.

Social

Unlike the vast majority of lizards, baby iguanas are social. When they can leave the nest, they usually do so in groups, thus forming a juvenile habitat, among the low bushes. Likewise, at least during the first year, they could maintain this social group.

In the adult stage, this animal is territorial, maintaining an overlap between the female and male territories. In the reproductive period, the dominant male notably reduces his territory.

To protect his space, he puts on displays of his supremacy. Likewise, it extends the gular sac, moves its head and keeps its body upright. With these behaviors he keeps other males away, thus guaranteeing him almost exclusive access to the reproductive females of the group.

Before copulation, the female invests her energy in producing a large number of eggs, so that they are fertilized. Contrary to this, the male focuses on his territory and fertilizing as many females as possible. In this way, it forms a kind of harem, maintaining and protecting the females that form it.

References

1. Wikipedia (2019). Iguana. Recovered from en.wikipedia.org.
2. Encyclopaedia Britannica (2019). Iguana. Recovered from britannica.com.
3. Brian C. Bock (2014). Iguana iguana. Recovered from iucn-isg.org,
4. The new world encyclopedia (2008). Iguana. Recovered from newworldencyclopedia.org.
5. Alina Bradford (2015). Iguana facts. Lives cience. Recovered from livescience.com,
6. Breuil, Michel. (2016). Morphological characterization of the common iguana Iguana iguana (Linnaeus, 1758), of the Lesser Antillean Iguana Iguana delicatissima Laurenti, 1768 and of their hybrids. Recovered from researchgate.net.
7. del Socorro Lara-López, Alberto González-Romero (2002), Feeding of the green iguana Iguana iguana (Squamata: Iguanidae) in La Mancha, Veracruz, Mexico. Recovered from scielo.org.mx.
8. Eglantina Leonor Solorzano, Aburto Suj Ey, Mariling Canales Valle (2009). Study of the anatomical structures of the green iguana species (iguana iguana) in Nicaragua. Retrieved from repository.una.edu.ni.