Chameleon
Chameleons | |
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Clockwise from top left: Furcifer pardalis and Brookesia micra
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Suborder: | Iguania |
Clade: | Acrodonta |
Family: | Chamaeleonidae Rafinesque, 1815 |
Genera | |
Native range of Chamaeleonidae |
Chameleons or chamaeleons (family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 200 species described as of June 2015.[1] The members of this family are best known for their distinct range of colours, being capable of colour-shifting camouflage. The large number of species in the family exhibit considerable variability in their capacity to change colour. For some, it is more of a shift of brightness (shades of brown); for others, a plethora of colour-combinations (reds, yellows, greens, blues) can be seen.
Chameleons are also distinguished by their
Chameleons are
Etymology
The English word chameleon (/kəˈmiːliən/ kuh-MEEL-ee-un) is a simplified spelling of Latin chamaeleōn,[4] a borrowing of the Greek χαμαιλέων (khamailéōn),[5] a compound of χαμαί (khamaí) "on the ground"[6] and λέων (léōn) "lion".[7][8][9]
Classification
In 1986, the family Chamaeleonidae was divided into two subfamilies,
While some authorities have previously preferred to use this subfamilial classification on the basis of the absence of evidence principle,[11] these authorities later abandoned this subfamilial division, no longer recognizing any subfamilies with the family Chamaeleonidae.[16]
In 2015, however, Glaw reworked the subfamilial division by placing only the genera Brookesia and Palleon within the Brookesiinae subfamily, with all other genera being placed in Chamaeleoninae.[1]
Change of color
Some chameleon species are able to change their
Colour change in chameleons has functions in camouflage, but most commonly in social signaling and in reactions to temperature and other conditions. The relative importance of these functions varies with the circumstances, as well as the species. Colour change signals a chameleon's physiological condition and intentions to other chameleons.[19][20] Because chameleons are ectothermic, another reason why they change colour is to regulate their body temperatures, either to a darker colour to absorb light and heat to raise their temperature, or to a lighter colour to reflect light and heat, thereby either stabilizing or lowering their body temperature.[21][22] Chameleons tend to show brighter colours when displaying aggression to other chameleons,[23] and darker colours when they submit or "give up".[24] Most chameleon genera (exceptions are Chamaeleo, Rhampholeon and Rieppeleon) have blue fluorescence in a species specific pattern in their skull tubercles and in Brookesia there is also some in tubercles on the body. The fluorescence is derived from bones that only are covered in very thin skin and it possibly serves a signaling role, especially in shaded habitats.[25]
Some species, such as Smith's dwarf chameleon and several others in the genus Bradypodion, adjust their colours for camouflage depending on the vision of the specific predator species (for example, bird or snake) by which they are being threatened.[26][27] In the introduced Hawaiian population of Jackson's chameleon, conspicuous colour changes that are used for communication between chameleons have increased whereas anti-predator camouflage colour changes have decreased relative to the native source population in Kenya where there are more predators.[28]
Chameleons have two superimposed layers within their skin that control their colour and thermoregulation. The top layer contains a lattice of guanine nanocrystals, and by exciting this lattice the spacing between the nanocrystals can be manipulated, which in turn affects which wavelengths of light are reflected and which are absorbed. Exciting the lattice increases the distance between the nanocrystals, and the skin reflects longer wavelengths of light. Thus, in a relaxed state the crystals reflect blue and green, but in an excited state the longer wavelengths such as yellow, orange, green, and red are reflected.[29]
The skin of a chameleon also contains some yellow pigments, which combined with the blue reflected by a relaxed crystal lattice results in the characteristic green colour which is common of many chameleons in their relaxed state. Chameleon colour palettes have evolved through evolution and the environment. Chameleons living in the forest have a more defined and colourful palette compared to those living in the desert or savanna, which have more of a basic, brown, and charred palette.[30]
Evolution
The oldest described chameleon is
The chameleons are probably far older than that, perhaps sharing a common ancestor with
Although nearly half of all chameleon species today live in Madagascar, this offers no basis for speculation that chameleons might originate from there.[32] In fact, it has recently been shown that chameleons most likely originated in mainland Africa.[15] It appears there were two distinct oceanic migrations from the mainland to Madagascar. The diverse speciation of chameleons has been theorized to have directly reflected the increase in open habitats (savannah, grassland, and heathland) that accompanied the Oligocene period. Monophyly of the family is supported by several studies.[33]
Daza et al. (2016) described a small (10.6 mm in snout-vent length), probably
While the exact evolutionary history of colour change in chameleons is still unknown, there is one aspect of the evolutionary history of chameleon colour change that has already been conclusively studied: the effects of signal efficacy. Signal efficacy, or how well the signal can be seen against its background, has been shown to correlate directly to the spectral qualities of chameleon displays.[37] Dwarf chameleons, the chameleon of study, occupy a wide variety of habitats from forests to grasslands to shrubbery. It was demonstrated that chameleons in brighter areas tended to present brighter signals, but chameleons in darker areas tended to present relatively more contrasting signals to their backgrounds. This finding suggests that signal efficacy (and thus habitat) has affected the evolution of chameleon signaling. Stuart-Fox et al. note that it makes sense that selection for crypsis is not seen to be as important as selection for signal efficacy, because the signals are only shown briefly; chameleons are almost always muted cryptic colours.[37]
Description
Chameleons vary greatly in size and body structure, with maximum total lengths varying from 22 mm (0.87 in) in male
Typical sizes of species of chameleon commonly kept in captivity or as pets are:
Scientific name | Common name | Length (male) | Length (female) | Colour | Lifespan (years) |
---|---|---|---|---|---|
Chamaeleo calyptratus | Veiled chameleon | 35–60 cm | 25–33 cm | Green and light colours | about 5 |
Trioceros jacksonii | Jackson's chameleon | 23–33 cm | 25–33 cm | Green and light colours | 5–10 |
Furcifer pardalis | Panther chameleon | 38–53 cm | 23–33 cm | Darker colours | about 5 (2–3 for birthing females) |
Rieppeleon brevicaudatus | Bearded pygmy chameleon | 5–8 cm | 5–8 cm | Brown, beige, green | about 3–5 |
Rhampholeon spectrum |
Spectral pygmy chameleon | 8–10 cm | 5–10 cm | Tan and gray | 3–5 |
Rhampholeon temporalis | Usambara pitted pygmy chameleon | 6–10 cm | 5–9 cm | Gray and brown | 5–11 |
The feet of chameleons are highly adapted to arboreal locomotion, and 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 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 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 vary between species and individuals. These spikes help break up the definitive outline of the chameleon, which aids it when trying to blend into a background.
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. Each eye can pivot and focus independently, allowing the chameleon to observe two different objects simultaneously. This gives them a full 360-degree arc of vision around their bodies. Prey is located using monocular depth perception, not stereopsis.[40] Chameleons have the highest magnification (per size) of any vertebrate,[41] with the highest density of cones in the retina.[42]
Like snakes, chameleons do not have an outer or a middle ear, so there is neither an ear-opening nor an eardrum. However, chameleons are not deaf: they can detect sound frequencies in the range of 200–600 Hz.[43]
Chameleons can see in both visible and
Feeding
All chameleons are primarily
The tongue apparatus consists of highly modified
Tongue projection occurs at extremely high performance, reaching the prey in as little as 0.07 seconds, The recoil of elastic elements in the tongue apparatus is 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.
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Tongue structure, with cup-like end
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Tongue begins strike
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Capturing prey
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Bringing prey to the mouth
Bones
Certain species of chameleons have bones that glow when under
Distribution and habitat
Chameleons primarily live in the mainland of
Chameleons are found only in
Reproduction
Most chameleons are
The oviparous species lay eggs three to six weeks after copulation. The female will dig a hole—from 10–30 cm (4–12 in), deep depending on the species—and deposit her eggs. Clutch sizes vary greatly with species. Small Brookesia species may only lay two to four eggs, while large veiled chameleons (Chamaeleo calyptratus) have been known to lay clutches of 20–200 (veiled chameleons) and 10–40 (panther chameleons) eggs. Clutch sizes can also vary greatly among the same species. Eggs generally hatch after four to 12 months, again depending on the species. The eggs of Parson's chameleon (Calumma parsoni) typically take 400 to 660 days to hatch.[57]
Chameleons lay flexible-shelled eggs which are affected by environmental characteristics during incubation. The egg mass is the most important in differentiating survivors of Chameleon during incubation. An increase in egg mass will depend on temperature and water potential.[58] To understand the dynamics of water potential in Chameleon eggs, the consideration of exerted pressure on eggshells will be essential because the pressure of eggshells play an important role in the water relation of eggs during entire incubation period [59]
The ovoviviparous species, such as the Jackson's chameleon (Trioceros jacksonii) have a five- to seven-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 hatched 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.[60]
Diet
Chameleons generally eat insects, but larger species, such as the common chameleon, may also take other lizards and young birds.[61]: 5 The range of diets can be seen from the following examples:
- The veiled chameleon, They can eat as many as 15–50 large crickets a day.
- Jackson's chameleon (Trioceros jacksonii) from Kenya and northern Tanzania eat 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.[60]
- 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.[61]: 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.[61]: 5–6
- Some chameleons like the UV component increases internal production.[63]
Anti-predator adaptations
Chameleons are preyed upon by a variety of other animals.
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(video) Chameleon in Malawi
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Chameleon found in Mysore, Southern India
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This common chameleon (Chamaeleo chamaeleon) turned black.
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A flap-necked chameleon, Chamaeleo dilepis, attacked by a boomslang while crossing a road in Namibia adopts a threatening defense posture.
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threat display, Namib-Naukluft National Park, turned black and opened its mouth when an attempt was made to move it off a busy road.
Parasites
Chameleons are
Chameleons are subject to several protozoan parasites, such as Plasmodium, which causes malaria, Trypanosoma, which causes sleeping sickness, and Leishmania, which causes leishmaniasis.[68]
Chameleons are subject to parasitism by coccidia,[68] including species of the genera Choleoeimeria, Eimeria, and Isospora.[69]
As pets
Chameleons are popular reptile pets, mostly imported from African countries like Madagascar, Tanzania, and Togo.
The U.S. has been the main importer of chameleons since the early 1980s accounting for 69% of African reptile exports.[70] However, there have been large declines due to tougher regulations to protect species from being taken from the wild and due to many becoming invasive in places like Florida.[70] They have remained popular though which may be due to the captive-breeding in the U.S. which has increased to the point that the U.S. can fulfill its demand, and has now even become a major exporter as well.[70] In the U.S. they are so popular, that despite Florida having six invasive chameleon species due to the pet trade, reptile hobbyists in these areas search for chameleons to keep as pets or to breed and sell them, with some selling for up to a thousand dollars.[3]
Historical understandings
Aristotle (4th century BC) describes chameleons in his History of Animals.[71] Pliny the Elder (1st century AD) also discusses chameleons in his Natural History,[72] noting their ability to change colour for camouflage.
The chameleon was featured in Conrad Gessner's Historia animalium (1563), copied from De aquatilibus (1553) by Pierre Belon.[73]
In Shakespeare's Hamlet, the eponymous Prince says "Excellent, i' faith, of the chameleon's dish. I eat the air, promise-crammed." This refers to the Elizabethan belief that chameleons lived on nothing but the air.
References
- ^ .
- National Geographic: 98.
- ^ a b Daly, Natasha (2017). "Inside the Secretive World of Florida's Chameleon Catchers". National Geographic. Archived from the original on November 9, 2020.
- Perseus Project.
- Perseus Project.
- ^ χαμαί in Liddell and Scott.
- ^ λέων in Liddell and Scott.
- ^ "Chameleon". Dictionary.com.
- ^ Harper, Douglas. "chameleon". Online Etymology Dictionary.
- ^ Klaver, C.; Böhme, W. (1986). "Phylogeny and classification of the Chamaeleonidae (Sauria) with special reference to hemipenis morphology". Bonner Zoologische Monographien. 22: 1–64.
- ^ ISBN 978-3899734515.
- PMID 12182400.
- S2CID 4422153.
- PMID 20826471.
- ^ PMID 23536596.
- ISBN 9780520276055.
- ^ Sharon Katz Cooper. "Chameleons". National Geographic Explorer. Archived from the original on 20 Aug 2008.
- ^ PMID 25757068.
- PMID 18232740.
- ^ Harris, Tom (18 May 2001). "How Animal Camouflage Works". How Stuff Works. Retrieved 2006-11-13.
- S2CID 80673490.
- ^ Cook, Maria. "The Adaptations of Chameleons". Sciencing. Retrieved 15 June 2020.
- PMID 24335271.
- S2CID 18606633.
- ^ PMID 29335580.
- ^ Young, Emma (2008) Chameleons fine-tune camouflage to predator's vision. New Scientist
- PMID 19000973.
- PMID 35544573.
- ^ Patricia Edmonds (2015). "The colourful Language of Chameleons". National Geographic Society. Archived from the original on 11 Mar 2016.
- PMID 18232740.
- ^ a b Maisano, Jessie (27 August 2003). "Chamaeleo calyptratus, Veiled Chameleon". Digimorph. University of Texas at Austin. Retrieved January 10, 2012.
- ISBN 978-1-77007-375-3.
- ISBN 9780520276055. Retrieved 1 November 2017 – via Google Books.
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- ^ Le Berre and Bartlett, p. 31
- ^ "Chamaeleon News". Chameleonnews.com. August 2004. Archived from the original on 22 January 2008. Retrieved 1 November 2017.
{{cite web}}
: CS1 maint: bot: original URL status unknown (link) - ^ ISBN 9780520276055
- ^ S2CID 21033176.
- ^ Anderson, Christopher V. (2009) Rhampholeon spinosus feeding video. chamaeleonidae.com
- ^ S2CID 3246256.
- ^ PMID 15209111.
- ^ ISBN 9780520276055
- ^ PMID 20212130.
- ^ PMID 23125336.
- PMID 11023845. Archived from the original(PDF) on 2010-06-20. Retrieved 2014-11-16.
- ^ a b Elaina Zachos (2018-01-18). "Chameleon Bones Glow in the Dark, Even Through Skin". National Geographic. Archived from the original on January 18, 2018. Retrieved 2018-08-03.
- ^ "Habitat loss and fragmentation reduce chameleon population in Tanzania". Phys.org. Retrieved 1 November 2017.
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- ^ Laube, Alexandra; Negro, Thorsten; Augustin, Andreas (2020). "781 days in the egg: Prolonged incubation time in Calumma parsonii parsonii (Cuvier, 1824) resulting in a healthy juvenile and revealing circumstantial evidence for sperm retention in this species". Herpetology Notes. 13: 425–428.
{{cite journal}}
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- ^ a b "African Rainforest". Jackson's Chameleon. Toronto Zoo. Archived from the original on November 11, 2011. Retrieved January 9, 2012.
- ^ a b c Dever, Jennifer (December 5, 2007). "Common Chameleon" (PDF). usfca.edu. Archived from the original (PDF) on February 3, 2015. Retrieved January 9, 2012.
- ^ "Reptiles and Amphibians: Veiled Chameleon". Smithsonian National Zoological Park. Archived from the original on 2011-12-17. Retrieved January 9, 2012.
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- ^ Le Berre and Bartlett, p. 110
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General bibliography
- Le Berre, François; Bartlett, Richard D. (2009). The Chameleon Handbook. Barron's Educational Series. 3rd Edition. ISBN 0764141422.
Further reading
- "Scientists find Madagascar chameleon last seen 100 years ago". Associated Press. 30 Oct 2020.
- Anderson, C. V.; Deban, S. M. (2010). "Ballistic tongue projection in chameleons maintains high performance at low temperature". Proceedings of the National Academy of Sciences of the United States of America. 107 (12): 5495–5499. PMID 20212130.
- Anderson, C. V.; Deban, S. M. (2012). "Thermal effects on motor control and in vitro muscle dynamics of the ballistic tongue apparatus in chameleons". Journal of Experimental Biology. 215 (24): 4345–4357. PMID 23125336.
- Anderson, C. V.; Sheridan, T.; Deban, S. M. (2012). "Scaling of the ballistic tongue apparatus in chameleons". Journal of Morphology. 273 (11): 1214–1226. S2CID 21033176.
- Davison, Linda J. Chameleons: Their Care and Breeding. Hancock House Publishers, 1997.
- 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 (1540): 761–770. PMID 15209111.
- de Vosjoli, Philippe. Essential Care of Chameleons. Advanced Vivarium Systems, 2004.
- 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 (2): 154–170. S2CID 3246256.
External links
- Media related to Chamaeleonidae at Wikimedia Commons
- Data related to Chamaeleonidae at Wikispecies