Chameleons (family Chamaeleonidae) are a specialist group of Old World lizards with 202 species as of June 2015. Such species come in a variety of colours, and many of them can change hues.
Chameleons are identified by their zygodactylous feet, swaying movement, and brow and snout crests or horns. Most species, especially the larger ones, have a prehensile tail. Chameleons' eyes are individually moveable, yet they focus forward in synchronisation when aiming at a prey item, giving the animal stereoscopic vision. Chameleons have evolved to climb and hunt by sight. They exist in a variety of warm settings, ranging from the rainforest to desert, and can be found in Africa, southern Europe, Madagascar, and southern Asia as far as Sri Lanka. California, Hawaii, and Florida have all been exposed to them.
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Change of Colour
Several chameleon animals have the ability to alter the colour of their skin. Chameleons may change their coloration and pattern by combining colours including light blue, pink, green, red, yellow, orange, blue, black, brown, turquoise, and purple. The skin of a chameleon has a pigmented surface layer and cells with guanine crystals beneath it. Chameleons change their colour by altering the distance between the guanine crystals, which inturn alters the wavelength of light reflected off the crystals, altering the skin's colour.
Chameleons use colour change for a variety of reasons, including camouflage and social signalling, as well as response to temperature as well as other environmental factors. The relative significance of such functions changes depending on the situation and the species. To other chameleons, a chameleon's physiological condition and intentions are communicated through colour change. Because chameleons are ectothermic, they change colour to regulate their body temperatures, either by absorbing light and heat to increase their temperature or by reflecting light and heat to stabilise or drop their temperature.
Chameleons exhibit brighter colours while expressing aggression toward other chameleons and darker colours when submitting or "giving up." Blue fluorescence within skull tubercles of certain species, especially those of Madagascar as well as some African genera in rainforest settings, is derived from bones and may serve as a communication mechanism.
1. Mechanism of Colour Change
Chameleons were supposed to change colour by dispersing pigment-containing organelles inside their epidermis for a long period of time. However, studies on panther chameleons in 2014 revealed that pigment migration is only one element of the mechanism.
Chameleons have two layers of skin that determine their colour and regulate their temperature. The upper surface includes a lattice of guanine nanocrystals that might be excited to change the spacing between the nanocrystals, affecting which wavelengths of light are reflected and which are absorbed. The skin reflects larger wavelengths of light as the lattice is excited, increasing the distance between the nanocrystals. The crystals reflect blue and green in a relaxed condition, but higher wavelengths including yellow, green, orange, and red are reflected in an aroused condition.
Chameleons range in size and body structure from 15 mm (0.59 in) in male Brookesia micra to 68.5 cm (27.0 in) in male Furcifer oustaleti. Numerous have nasal protrusions or horn-like projections on their heads, as in the case of Trioceros jacksonii, or enormous crests on top of their heads, as in Chamaeleo calyptratus. Male chameleons are often significantly more decorated than female chameleons, and several species are sexually dimorphic.
Chameleons have had the most distinguishing eyes of any reptile species. Only a pinhole wide enough for the pupil seeing through connects the top and bottom eyelids. The chameleon's eyes can rotate and focus individually, letting it examine two separate objects at the same time. This allows them to see around their bodies in a full 360-degree arc. Monocular depth perception, not stereopsis, is used to locate prey. Chameleons possess excellent eyesight for reptiles, allowing them to see minute insects from a distance of 5–10 metres. Chameleons, in reality, have the greatest magnification (per unit of size) of any vertebrate.
Chameleons, like snakes, may not have an outer or middle ear, hence there is no ear hole or eardrum. Chameleons, on the other hand, are not deaf; they could sense sound frequencies between 200 and 600 Hz. Both visible and ultraviolet light are visible to chameleons. Because UV light has a favourable effect on the pineal gland, chameleons subjected to it exhibit greater social behaviour and activity, are far more willing to bask and feed, and are much more inclined to procreate.
Chameleons are predominantly insectivores, which feed by thrusting their long tongues from their mouths in a ballistic motion to acquire prey that is some significant distance. Whereas the tongues of chameleons are usually one and a half to two times the length of their bodies, smaller chameleons have lately been discovered to have substantially bigger tongue apparatuses than its larger counterparts. Smaller chameleons could project their tongues further than the larger chameleons studied in most research and tongue length estimates, and therefore can extend their tongues more than double their body size.
Under ultraviolet light, the bones of some chameleon species shine, a phenomenon known as biogenic fluorescence. This fluorescence was seen in CT scans of 31 different species of Calumma chameleons, all of which are native to Madagascar. The bones created a vivid blue glow that could be seen through all 4 levels of the chameleon's skin. The face was discovered to have a distinct glow, which appeared as spots on the facial bones termed as tubercles. The glow is caused by pigments, proteins, chitin, and other components that make up a chameleon's skeleton, and could have developed through sexual selection to provide chameleons with a secondary signalling mechanism which does not interfere with their color-changing abilities.
The majority of chameleons are oviparous, while few are ovoviviparous.
After copulation, oviparous species tend to lay eggs three to six weeks later. The female will lay her eggs in a hole that is 10–30 cm (4–12 in) deep, based upon the species. The size of a clutch varies widely depending on the species. Giant veiled chameleons (Chamaeleo calyptratus) have indeed been found to deposit clutches of 20–200 (veiled chameleons) and 10–40 (panther chameleons) eggs, whereas small Brookesia species may just produce two to four eggs. Clutch sizes could also differ dramatically between species. Based on the variety, eggs usually hatch after four to twelve months. The eggs of the Parson's chameleon (Calumma parsonii), an uncommon in captive species, are said to require almost one year to hatch.
Chameleons produce flexible-shelled eggs that are influenced by their surroundings throughout incubation. The egg mass has been the most critical factor in distinguishing Chameleon survival throughout incubation.
Chameleons eat insects primarily, but larger species, including the common chameleon, might even devour lizards and young birds. The following are some instances of different diets:
The Arabian veiled chameleon, Chamaeleo calyptratus, is insectivorous, however when alternative sources of water are unavailable, it eats leaves. On a diet of crickets, it could be kept alive. They may consume up to 15–50 huge crickets in a single day.
Small animals including amphibians, snails, ants, caterpillars, butterflies, geckos, worms, lizards, and other chameleons, and also plant material including delicate shoots, leaves, and berries, are eaten by the Jackson's chameleon (Trioceros jacksonii) of Kenya and northern Tanzania. Kale, apples, lettuce, dandelion leaves, tomatoes, bananas, crickets, and waxworms are all good sources of protein.
Chamaeleo chamaeleon, the typical chameleon of North Africa, Europe, and the Near East, feeds primarily on wasps and mantises, accounting for over three-quarters of its diet.
The quantity of food consumed is influenced by the temperature.
Certain chameleons, such as the Madagascar panther chameleon, manage their vitamin D3 levels by introducing themselves to sunshine, this stimulates internal production of the vitamin, which their insect diet is deficient in.
Predation and Defence
Chameleons are preyed on and eaten by a wide range of predators. The most common predators of adult chameleons are birds and snakes. Chameleon eggs and juveniles are preyed upon heavily by invertebrates, particularly ants. Chameleons are unlikely to be able to flee predators and must depend on crypsis to protect themselves. Chameleons may change their colours and patterns (to varied degrees) to blend in with their environment or distort their body outline to avoid being seen by a possible predator. Chameleons only fight themselves if they are detected. They adopt a protective body stance, flatten their bodies laterally to appear larger, alert via an open mouth, and, if necessary, strike back with their feet and jaws. When it comes to threat displays, vocalisation is occasionally used.
The Indian chameleon (Chamaeleo zeylanicus) is a chameleon species native to India, Sri Lanka, and South Asia. This species, like many other chameleons, does have independent eye movement, a long tongue, a prehensile tail, bifid clasper foot, and the power to change color of skin. They are arboreal and move slowly with a bobbing or swaying motion. Surprisingly, they don't choose the background colour and might not be able to distinguish between colours. They are generally green or brown in colour, with bands. They have the ability to change colour quickly, and their major purpose is to communicate with other chameleons and to regulate body temperature by shifting to dark colours to absorb the heat.
The head is covered with a bony casque with tubercles or crests. The interorbital septum, which separates the eyes, is present. It has an acrodont dentition, with compressed, triangular, and almost obviously tricuspid teeth. The palate is devoid of teeth. The eyes are big, with thick, granular lids that are pierced with a centrally located pupil aperture. There is no tympanum or external ear. The body is squished together, and the neck is quite short. The vertebrae are procoelian, and there are abdominal ribs. The body is raised by the lengthy limbs. The digits are organized in two and three-digit bundles; in the hand, the inner bundle is made up of three digits, while the outer bundle is made up of two digits; in the foot, the opposite is true. Precisely, the tail is prehensile.
Brookesia micra, also called as the Nosy Hara leaf chameleon, is a chameleon species native to Madagascar's Antsiranana islet. This was the world's smallest chameleon and one of the tiniest reptiles (tiny chameleon) at the time of its discovery, until the much smaller B. nana was discovered in 2021. Adult B. micra can reach a length of 29 mm (1.1 in).
The Parson's chameleon (Calumma parsonii) is a big chameleon species belonging to the Chamaeleonidae family of lizards. The species is only found in a few isolated pockets of wet primary forest in Madagascar's eastern and northern regions. Because it is listed on CITES Appendix II, commerce in this species is restricted. Although most chameleon species from Madagascar are prohibited from being legally transported, a small number of Parson's chameleons could be lawfully exported from Madagascar per year.