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Chameleon From Wikipedia, the free encyclopedia For other uses, see Chameleon (disambiguation). Chameleon

Cape Dwarf Chameleon (Bradypodion pumilum) female Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Squamata Suborder: Lacertilia Infraorder: Iguania Family: Chamaeleonidae Subfamilies and Genera Chamaeleoninae Archaius Bradypodion Calumma Chamaeleo Furcifer Kinyongia Nadzikambia Trioceros Brookesiinae Brookesia Rieppeleon Rhampholeon Chameleons (family Chamaeleonidae) are a distinctive and highly specialized clade of lizards. The approximately 160 species of chameleon come in a variety of colors, including pink, blue, red, orange, turquoise, yellow, and green. They are distinguished by their zygodactylous feet; their separately mobile, stereoscopic eyes; their very long, highly modified, rapidly extrudable tongues; their swaying gait; and crests or horns on their distinctively shaped heads. Some species can change color, and many have a prehensile tail. Uniquely adapted for climbing and visual hunting, they are found in warm habitats that vary from rain forest to desert conditions--in Africa, Madagascar, and southern Europe, and across south Asia as far as Sri Lanka. They have also been introduced to Hawaii, California, and Florida, and are often kept as household pets. Contents [hide] 1 Etymology 2 Classification 3 Evolution 4 Description 4.1 Senses 4.2 Feeding 5 Distribution and habitat 6 Reproduction 7 Diet 8 Change of color 8.1 Mechanism of color change 9 Parasites 10 Video 11 Footnotes 12 References 13 Further reading 13.1 Popular books 14 External links [edit]Etymology

The English word chameleon (also chamaeleon) derives from Latin chamaeleō, a borrowing of the Greek χαμαιλέων (khamailéōn),[1] a compound of χαμαί (khamaí) "on the ground"[2] and λέων (léōn) "lion".[3] [4] The Greek word is a calque translating the Akkadian nēš qaqqari, literally 'lion ground' (adjectives follow nouns in Akkadian).[citation needed] [edit]Classification

Family Chamaeleonidae Subfamily Brookesiinae Subfamily Chamaeleoninae [edit]Evolution

The oldest known chameleon is Anqingosaurus brevicephalus from the Middle Paleocene (about 58.7–61.7 mya) of China.[5] Other chameleon fossils include Chamaeleo caroliquarti from the Lower Miocene (about 13–23 mya) of the Czech Republic and Germany, and Chamaeleo intermedius from the Upper Miocene (about 5–13 mya) of Kenya.[5] The chameleons are probably far older than that, perhaps sharing a common ancestor with iguanids and agamids more than 100 mya (agamids being more closely related). Since fossils have been found in Africa, Europe and Asia, chameleons were certainly once more widespread than they are today. Although nearly half of all chameleon species today are found in Madagascar, this offers no basis for speculation that chameleons might originate from there.[6] Monophyly of the family is supported by several studies.[citation needed] [edit]Description

Malagasy giant chameleon, Ambalavao, Madagascar

Cape dwarf chameleon in the act of defecation: The typical action by which it avoids fouling its own branch incidentally displays the difference between the arrangement of its fore and hind toes. Chameleons vary greatly in size and body structure, with maximum total lengths varying from 15 mm (0.59 in) in male Brookesia micra (one of the world's smallest reptiles) to 68.5 cm (27.0 in) in the male Furcifer oustaleti.[7][8] Many have head or facial ornamentation, such as nasal protrusions, or horn-like projections in the case of Trioceros jacksonii, or large crests on top of their heads, like Chamaeleo calyptratus. Many species are sexually dimorphic, and males are typically much more ornamented than the female chameleons. Typical sizes of species of chameleon commonly kept as pets are: Scientific name Common name Length (male) Length (female) Color Lifespan (years) Chamaeleo calyptratus Veiled chameleon 14–24 in 10–13 in Green and light colors about 5 Trioceros jacksonii Jackson's chameleon 9–13 in 10–13 in Green and light colors 5–10 Furcifer pardalis Panther chameleon 15–21 in 9–13 in Darker colors about 5 (2–3 for birthing females) Rieppeleon brevicaudatus Bearded pygmy chameleon 2–3 in 2–3 in Brown, beige, green about 3–5 Rhampholeon spectrum Spectral pygmy chameleon 3–4 in 2–4 in Tan and gray Unknown Rhampholeon temporalis Usumbara pitted pygmy chameleon 2.5–4.0 in 2.0–3.5 in Gray and brown Unknown The feet of chameleons are highly adapted to arboreal locomotion, though species such as Chamaeleo namaquensis, that have secondarily adopted a terrestrial habit, have retained the same foot morphology with little modification. On each foot, the five clearly distinguished toes are grouped into two fascicles. The toes in each fascicle are bound into a flattened group of either two or three, giving each foot a tongs-like appearance. On the front feet, the outer, lateral, group contains two toes, whereas the inner, medial, group contains three. On the rear feet, this arrangement is reversed, the medial group containing two toes, and the lateral group three. These specialized feet allow chameleons to grip tightly onto narrow or rough branches. Furthermore, each toe is equipped with a sharp claw to afford a grip on surfaces such as bark when climbing. It is common to refer to the feet of chameleons as didactyl or zygodactyl, though neither term is fully satisfactory, both being used in describing totally different feet, such as the zygodactyl feet of parrots or didactyl feet of sloths or ostriches, none of which is significantly like chameleon feet. Although "zygodactyl" is reasonably descriptive of chameleon foot anatomy, their foot structure does not resemble that of parrots, to which the term was first applied. As for didactyly, chameleons visibly have five toes on each foot, not two. Some chameleons have a crest of small spikes extending along the spine from the proximal part of the tail to the neck; both the extent and size of the spikes varies between species and individuals. These spikes help break up the definitive outline of the chameleon, which aids it when trying to blend in to a background. [edit]Senses Chameleons have the most distinctive eyes of any reptile. The upper and lower eyelids are joined, with only a pinhole large enough for the pupil to see through. They can rotate and focus separately to observe two different objects simultaneously; their eyes move independently from each other. This gives them a full 360-degree arc of vision around their bodies. Prey is located using monocular depth perception, not stereopsis. [9] Chameleons have very good eyesight for reptiles, letting them see small insects from a 5– to 10-m distance.[citation needed] Like snakes, chameleons do not have an outer or a middle ear, so there is neither an ear opening nor an eardrum.[10]:31 However, chameleons are not deaf: they can detect sound frequencies in the range of 200–600 Hz.[10]:31 Chameleons can see in both visible and ultraviolet light.[11] Chameleons exposed to ultraviolet light show increased social behavior and activity levels, are more inclined to bask and feed, and are also more likely to reproduce, as it has a positive effect on the pineal gland. [edit]Feeding

Tongue structure Chameleons feed by ballistically projecting their long tongues from their mouths to capture prey located some distance away. While the chameleon’s tongue is typically thought to be one and a half to two times the length of their bodies (their length excluding the tail), smaller chameleons (both smaller species and smaller individuals of the same species) have recently been found to have proportionately larger tongue apparatuses than their larger counterparts.[12] Thus, smaller chameleons are able to project their tongues greater distances than the larger chameleons that are the subject of most studies and tongue length estimates, and can project their tongues more than twice their body length.[13] The chameleon tongue apparatus consists of highly modified hyoid bones, tongue muscles and collagenous elements.[14][15][12] The hyoid bone has an elongated, parallel-sided projection, called the entoglossal process, over which a tubular muscle, the accelerator muscle, sits.[14][15][12] The accelerator muscle contracts around the entoglossal process and is responsible for creating the work to power tongue projection, both directly and through the loading of collagenous elements located between the entoglossal process and the accelerator muscle.[14][15][12] The tongue retractor muscle, the hyoglossus, connects the hyoid and accelerator muscle, and is responsible for drawing the tongue back into the mouth following tongue projection.[14][12] Tongue projection occurs at extremely high performance, reaching the prey in as little as 0.07 seconds,[14][15][16] having been launched at accelerations exceeding 41 g.[16] The power with which the tongue is launched, known to exceed 3000 W kg-1, exceeds that for which muscle is able to produce, indicating the presence of an elastic power amplifier to power tongue projection.[15] The recoil of elastic elements in the tongue apparatus are thus responsible for large percentages of the overall tongue projection performance. One consequence of the incorporation of an elastic recoil mechanism to the tongue projection mechanism is relative thermal insensitivity of tongue projection relative to tongue retraction, which is powered by muscle contraction alone, and is heavily thermally sensitive.[16] While other ectothermic animals become sluggish as their body temperatures decline, due to a reduction in the contractile velocity of their muscles, chameleons are able to project their tongues at high performance even at low body temperatures.[16] The thermal sensitivity of tongue retraction in chameleons, however, is not a problem, as chameleons have a very effective mechanism of holding onto their prey once the tongue has come into contact with it, including surface phenomena, such as wet adhesion and interlocking, and suction.[17] The thermal insensitivity of tongue projection thus enables chameleons to feed effectively on cold mornings prior to being able to behaviorally elevate their body temperatures through thermoregulation, when other sympatric lizards species are still inactive, likely temporally expanding their thermal niche as a result.[16] [edit]Distribution and habitat

The tiny, usually brown-colored Brookesia which include about 30 different species of chameleons are mainly terrestrial Chameleons are primarily found in the mainland of sub-Saharan Africa and on the island of Madagascar, although a few species are also found in northern Africa, southern Europe, the Middle East, southern India, Sri Lanka and several smaller islands in the western Indian Ocean. There are introduced, feral populations of veiled and Jackson's chameleons in Hawaii and isolated pockets of feral Jackson's chameleons have been reported in California and Florida. Chameleons inhabit all kinds of tropical and mountain rain forests, savannas and sometimes deserts and steppes. The typical chameleons from the subfamily Chamaeleoninae are arboreal and usually found in trees or bushes, although a few (notably the Namaqua Chameleon) are partially or largely terrestrial. Most species from the subfamily Brookesiinae, which includes the genera Brookesia, Rieppeleon and Rhampholeon, live low in vegetation or on the ground among leaf litter. Many species of chameleon are threatened by extinction. Declining chameleon numbers are due to pollution and deforestation.[citation needed] [edit]Reproduction

West Usambara Two-Horned Chameleon (Kinyongia multituberculata) in the Usambara mountains, Tanzania. Chameleons are mostly oviparous, some being ovoviviparous. The oviparous species lay eggs 3–6 weeks after copulation. The female will climb down to the ground and begin digging a hole, anywhere from 10–30 cm (4–12 in.) deep depending on the species. The female turns herself around at the bottom of the hole and deposits her eggs. Clutch sizes vary greatly with species. Small Brookesia species may only lay 2–4 eggs, while large Veiled Chameleons (Chamaeleo calyptratus) have been known to lay clutches of 80–100 eggs. Clutch sizes can also vary greatly among the same species. Eggs generally hatch after 4–12 months, again depending on species. The eggs of Parson's Chameleon (Calumma parsonii), a species which is rare in captivity, are believed to take upwards of 24 months to hatch.[citation needed] The ovoviviparous species, such as the Jackson's Chameleon (Trioceros jacksonii) have a 5–7 month gestation period. Each young chameleon is born within the sticky transparent membrane of its yolk sac. The mother presses each egg onto a branch, where it sticks. The membrane bursts and the newly born chameleon frees itself and climbs away to hunt for itself and hide from predators. The female can have up to 30 live young from one gestation.[18] [edit]Diet

Chameleons generally eat insects, but larger species such as the Common Chameleon may also take other lizards and young birds.[19]:5 The range of diets can be seen from the following examples: The Veiled Chameleon, Chamaeleo calyptratus from Arabia, is insectivorous, but eats leaves when other sources of water are not available. It can be maintained on a diet of Crickets. [20] They can eat as many as 15-50 large crickets a day. Jackson's Chameleon (Trioceros jacksonii) from Kenya and northern Tanzania eats a wide variety of small animals including ants, butterflies, caterpillars, snails, worms, lizards, geckos, amphibians and other chameleons, as well as plant material such as leaves, tender shoots, and berries. It can be maintained on a mixed diet including kale, dandelion leaves, lettuce, bananas, tomatoes, apples, crickets, and waxworms.[18] The Common Chameleon of Europe, North Africa, and the Near East, Chamaeleo chamaeleon, mainly eats wasps and mantises; such arthropods form over three quarters of its diet.[19]:5 Some experts advise that the Common Chameleon should not be fed exclusively on Crickets: these should make up no more than half the diet, with the rest a mixture of waxworms, earthworms, grasshoppers, flies, and plant materials such as green leaves, oats, and fruit.[19]:5-6 Temperature influences the amount of food eaten. [edit]Change of color

Further information: Animal coloration, Signaling theory

Camouflage of a Common Chameleon in its natural environment (vicinity of Oueslatia, Tunisia)

This Common Chameleon (Chamaeleo chamaeleon) turned black Some chameleon species are able to change their skin colors. Different chameleon species are able to change different colors which can include pink, blue, red, orange, green, black, brown, light blue, yellow, turquoise and purple.[21] Color change in chameleons has functions in social signaling and in reactions to temperature and other conditions as well as camouflage. The relative importance of the classes of function vary with the circumstances as well as the species. Color change signals a chameleon's physiological condition and intentions to other chameleons.[22][23] Chameleons tend to show darker colors when angered, or attempting to scare or intimidate others, while males show lighter, multi-colored patterns when courting females.[citation needed] Some species, such as Smith's dwarf chameleon, adjust their colors for camouflage in accordance with the vision of the specific predator species (bird or snake) that they are being threatened by.[24] The desert dwelling Namaqua Chameleon also uses color change as an aid to thermoregulation, becoming black in the cooler morning to absorb heat more efficiently, then a lighter grey color to reflect light during the heat of the day. It may show both colors at the same time, neatly separated left from right by the spine.[citation needed] [edit]Mechanism of color change Further information: Animal coloration and Category:Animals that can change color Chameleons have specialized cells, chromatophores, which contain pigments in their cytoplasm, in three layers below their transparent outer skin: The cells in the upper layer, called xanthophores and erythrophores, contain yellow and red pigments respectively. Below these is a second layer of cells called iridophores or guanophores; these contain guanine, appearing blue or white. The deepest layer of cells, melanophores, contain the dark pigment melanin, controlling how much light is reflected. Dispersion of the pigment granules in the chromatophores sets the intensity of each color. When the pigment is equally distributed in a chromatophore, the whole cell is intensively colored. When the pigment is located only in the centre of the cell, the cell appears mainly transparent. Chromatophores can rapidly relocate their particles of pigment, thereby influencing the animal's color. Chromatophores change because the cells get a message from the brain.[25] [edit]Parasites

Chameleons are parasitised by nematode worms including threadworms (Filaria) and roundworms. Threadworms can be transmitted by biting insects such as ticks and mosquitoes. Roundworms are transmitted through food contaminated with roundworm eggs; the larvae burrow through the wall of the intestine into the bloodstream.[26] Chameleons are subject to several protozoan parasites such as Plasmodium which causes malaria, Trypanosoma which causes sleeping sickness, and Leishmania which causes leishmaniasis.[27] Chameleons are subject to parasitism by coccidia,[27] including species of the genera Choleoeimeria, Eimeria and Isospora.[28] [edit]Video

[edit]Footnotes

^ χαμαιλέων, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus ^ χαμαί, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus ^ λέων, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus ^ Dictionary.com entry for "chameleon" ^ a b Maisano, Jessie (27 August 2003). "Digimorph". Chamaeleo calyptratus, Veiled Chameleon. University of Texas at Austin. Retrieved January 10, 2012. ^ Tolley, Krystal; Burger, Marius (2007). Chameleons of Southern Africa. Struik. pp. 26–28. ISBN 1-77007-375-2. ^ Glaw, Frank; Vences, Miguel (1994). A Field Guide to Amphibians and Reptiles of Madagascar 2nd edition. Köln: M. Vences & F. Glaw Verlags GbR. ISBN 3-929449-01-3. ^ Longbottom, Wil. "Discovered: The mini-meleon that is one of the smallest reptiles on the planet". Daily Mail. ^ Ott, M.; F. Schae€el, W. Kirmse (1998). "Binocular vision and accommodation in prey-catching chamaeleons". Comparative Physiology A 182: 319-330. ^ a b Le Berre and Bartlett, 2009 ^ Chamaeleon News, August 2004 ^ a b c d e Anderson, C.V., Sheridan, T. & Deban, S.M. (2012). "Scaling of the ballistic tongue apparatus in chameleons". Journal of Morphology 273: 1214–1226. doi:10.1002/jmor.20053. ^ [1] Rhampholeon spinosus feeding video by Christopher V. Anderson ^ a b c d e Herrel, A., Meyers, J.J., Nishikawa, K.C. & De Vree, F. (2001). "Morphology and histochemistry of the hyolingual apparatus in chameleons". Journal of Morphology 249: 154–170. ^ a b c d e de Groot, J.H. & van Leeuwen, J.L. (2004). "Evidence for an elastic projection mechanism in the chameleon tongue". Proceedings of the Royal Society of London B 271: 761–770. ^ a b c d e Anderson, C.V. and Deban, S.M. (2010). "Ballistic tongue projection in chameleons maintains high performance at low temperature". Proceedings of the National Academy of Science of the United States of America 107: 5495–5499. doi:10.1073/pnas.0910778107. ^ Herrel, A., Meyers, J.J., Aerts, P. & Nishikawa, K.C. (2000). "The mechanics of prey prehension in chameleons". Journal of Experimental Biology 203: 3255–3263. ^ a b "African Rainforest". Jackson's Chameleon. Toronto Zoo. Retrieved January 9, 2012. ^ a b c Dever, Jennifer (December 5, 2007). "Common Chameleon". Common Chameleon. usfca.edu. Retrieved January 9, 2012. ^ "Reptiles and Amphibians". Veiled Chameleon. Smithsonian National Zoological Park. Retrieved January 9, 2012. ^ National Geographic Explorer (Student Magazine) - Featured Article ^ Stuart-Fox, D., & Moussalli, A. (2008). Selection for social signaling drives the evolution of chameleon color change. Public Library of Science Biology, 6, e25. ^ Harris, Tom. "How Animal Camouflage Works". How Stuff Works. Retrieved 2006-11-13. ^ Emma Young (2008). Chameleons fine-tune camouflage to predator's vision. New Scientist ^ geographic, national. "chameleon camouflage". Retrieved 25 October 2011. ^ Le Berre and Bartlett, 2009. page 110 ^ a b Le Berre and Bartlett, 2009. page 109 ^ Sloboda, Michal and David Modrý (2006). "New species of Choleoeimeria (Apicomplexa: Eimeriidae) from the veiled chameleon, Chamaeleo calyptratus (Sauria: Chamaeleonidae), with taxonomic revision of eimerian coccidia from chameleons". FOLIA PARASITOLOGICA 53: 91–97. [edit]References

Anderson, C.V. & Deban, S.M. (2010): Ballistic tongue projection in chameleons maintains high performance at low temperature. Proceedings of the National Academy of Science of the United States of America 107 (12): 5495–5499. doi:10.1073/pnas.0910778107 Anderson, C.V., Sheridan, T. & Deban, S.M. (2012): Scaling of the ballistic tongue apparatus in chameleons. Journal of Morphology 273: 1214–1226. doi:10.1002/jmor.20053 de Groot, J.H. & van Leeuwen, J.L. (2004): Evidence for an elastic projection mechanism in the chameleon tongue. Proceedings of the Royal Society of London B 271: 761–770. doi:10.1098/rspb.2003.2637 Herrel, A., Meyers, J.J., Nishikawa, K.C. & De Vree, F. (2001): Morphology and histochemistry of the hyolingual apparatus in chameleons. Journal of Morphology 249: 154–170. [edit]Further reading

[edit]Popular books François Le Berre and Richard D. Bartlett. The Chameleon Handbook. Barron's Educational Series. 3rd Edition, 2009. Linda J. Davison. Chameleons: Their Care and Breeding. Hancock House Publishers, 1997. Philippe de Vosjoli. Essential Care of Chameleons. Advanced Vivarium Systems, 2004.