Editing Chameleon (section)

==Description==
[[File: Chameleon in Berenty Madagascar 0001.JPG|thumb|right|Nearly all species of chameleon have prehensile tails, but they most often grip with the tail when they cannot use all four feet at once, such as when passing from one twig to another.]]

Chameleons vary greatly in size and body structure, with maximum total lengths varying from {{convert|22|mm|in|sp=us|abbr=on}} in male ''[[Brookesia nana]]'' (one of the world's [[Smallest organisms#Lizards and snakes (Squamata)|smallest reptiles]]) to {{convert|68.5|cm|in|sp=us|abbr=on}} in the male ''[[Furcifer oustaleti]]''.<ref>{{Cite journal |last1=Glaw|first1=Frank|last2=Köhler|first2=Jörn|last3=Hawlitschek|first3=Oliver|last4=Ratsoavina|first4=Fanomezana M.|last5=Rakotoarison|first5=Andolalao|last6=Scherz|first6=Mark D.|last7=Vences|first7=Miguel |name-list-style=amp |date=28 January 2021|title=Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons|url= |journal=Scientific Reports|language=en|volume=11|issue=1|pages=2522|doi=10.1038/s41598-020-80955-1 |pmc=7844282|pmid=33510189}}</ref><ref name=GlawVences1994>{{cite book |last=Glaw |first=Frank |author2=Vences, Miguel |title=A Field Guide to Amphibians and Reptiles of Madagascar |edition=2 |page=253 |publisher=Verlags GbR |year=1994 |location=Köln |isbn=978-3-929449-01-3 }}</ref> 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 in captivity or as pets are:

{|class="wikitable sortable" caption="Typical sizes of some chameleon species"
|-
! Scientific name !! Common name !! Length (male) !! Length (female) !! Colour !! Lifespan (years)
|-
|''[[Veiled chameleon|Chamaeleo calyptratus]]'' ||[[Veiled chameleon]] ||35–60&nbsp;cm ||25–33&nbsp;cm ||Green and light colours ||about 5
|-
|''[[Jackson's chameleon|Trioceros jacksonii]]'' ||[[Jackson's chameleon]] ||23–33&nbsp;cm ||25–33&nbsp;cm ||Green and light colours ||5–10
|-
|''[[Panther chameleon|Furcifer pardalis]]'' ||[[Panther chameleon]] ||38–53&nbsp;cm ||23–33&nbsp;cm ||Darker colours ||about 5 (2–3 for birthing females)
|-
|''[[Rieppeleon brevicaudatus]]'' ||[[Rieppeleon brevicaudatus|Bearded pygmy chameleon]] ||5–8&nbsp;cm ||5–8&nbsp;cm ||Brown, beige, green ||about 3–5
|-
|''[[Rhampholeon spectrum]]'' ||[[Spectral pygmy chameleon]] ||8–10&nbsp;cm ||5–10&nbsp;cm ||Tan and gray ||3–5
|-
|''[[Rhampholeon temporalis]]'' ||[[Rhampholeon temporalis|Usambara pitted pygmy chameleon]] ||6–10&nbsp;cm ||5–9&nbsp;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, [[Anatomical terms of location|lateral]], group contains two toes, whereas the inner, [[Anatomical terms of location|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 [[Dactyly|didactyl]] or [[Dactyly|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 [[neural spine sail|crest of small spikes]] extending along the spine from the [[Anatomical terms of location|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===
{{Further|Chameleon vision}}
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]].<ref name="ott">{{cite journal |last1=Ott |first1=M. |last2=Schaeffel |first2=F. |last3=Kirmse |first3=W. |title=Binocular vision and accommodation in prey-catching chamaeleons |journal= Journal of Comparative Physiology A |year=1998 |volume=182 |issue=3 |pages=319–330 |doi=10.1007/s003590050182 |s2cid=19988312 }}</ref> Chameleons have the highest magnification (per size) of any vertebrate,<ref>{{cite journal | doi=10.1038/373692a0 | title=A negatively powered lens in the chameleon | year=1995 | last1=Ott | first1=Matthias | last2=Schaeffel | first2=Frank | journal=Nature | volume=373 | issue=6516 | pages=692–694 | pmid=7854450 | bibcode=1995Natur.373..692O | s2cid=4262985 }}</ref> with the highest density of [[Cone cell|cones]] in the [[retina]].<ref>{{cite book |last1=Stuart-Fox |first1=Devi |chapter=Chameleon Behavior and Color Change |editor1-last=Tolley |editor1-first=Krystal A. |editor2-last=Herrel |editor2-first=Anthony |title=The Biology of Chameleons |publisher=University of California Press |year=2014 |location=Berkeley |pages=115–130 |isbn=9780520276055 }}</ref>

Like [[snake]]s, 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&nbsp;Hz.<ref>Le Berre and Bartlett, p. 31</ref>

Chameleons can see in both visible and [[ultraviolet light]].<ref>{{cite web|url=http://www.chameleonnews.com/lighting1.html |title=Chamaeleon News |date=August 2004 |website=Chameleonnews.com |access-date=1 November 2017 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20080122143034/http://www.chameleonnews.com/lighting1.html |archive-date=22 January 2008}}</ref> Chameleons exposed to ultraviolet light show increased social behavior and activity levels, are more inclined to bask, feed, and reproduce as it has a positive effect on the [[pineal gland]].

===Feeding===
All chameleons are primarily [[insectivore]]s that feed by [[projectile use by living systems|ballistically projecting]] their long [[tongue]]s from their mouths to capture prey located some distance away.<ref name="Higham and Anderson 2014">{{Citation |last1= Higham |first1= T. E. |last2= Anderson |first2= C. V. |contribution= Function and adaptation of chameleons |editor-last= Tolley |editor-first= K. A. |editor-last2= Herrel |editor-first2= A. |title= The Biology of Chameleons |pages= 63–83 |publisher= University of California Press |place=Berkeley, CA |year= 2014 |isbn=9780520276055}}</ref> While the chameleons' tongues are 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.<ref name="Anderson et al. 2012">{{cite journal |doi=10.1002/jmor.20053 |pmid= 22730103 |title= Scaling of the ballistic tongue apparatus in chameleons |author1= Anderson, C. V.|author2= Sheridan, T. |author3= Deban, S. M. |journal=Journal of Morphology |year=2012 |volume=273 |issue= 11 |pages=1214–1226 |s2cid= 21033176 }}</ref> 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.<ref>Anderson, Christopher V. (2009) [http://www.chamaeleonidae.com/Movies/Pages/Rhampholeon_spinosus.html ''Rhampholeon spinosus'' feeding video]. chamaeleonidae.com</ref>

The tongue apparatus consists of highly modified [[Hyoid|hyoid bones]], [[Muscles of tongue|tongue muscles]], and [[Collagen|collagenous elements]].<ref name="Herrel et al. 2001">{{cite journal |title= Morphology and histochemistry of the hyolingual apparatus in chameleons |author= Herrel, A. |author2= Meyers, J. J.|author3= Nishikawa, K. C. |author4= De Vree, F. |journal=Journal of Morphology |year=2001 |volume=249 |issue= 2 |pages=154–170 |doi=10.1002/jmor.1047|pmid= 11466743 |s2cid= 3246256 }}</ref><ref name="de Groot & van Leeuwen 2004">{{cite journal |title= Evidence for an elastic projection mechanism in the chameleon tongue |author1=de Groot, J. H. |author2=van Leeuwen, J. L. |journal=Proceedings of the Royal Society of London B |year=2004 |volume=271 |issue= 1540 |pages=761–770 |doi=10.1098/rspb.2003.2637 |pmid=15209111 |pmc=1691657 }}</ref><ref name="Anderson et al. 2012"/><ref name="Anderson and Higham 2014">{{Citation |last1= Anderson |first1= C. V. |last2= Higham |first2= T. E. |contribution= Chameleon anatomy |editor-last= Tolley |editor-first= K. A. |editor-last2= Herrel |editor-first2= A. |title= The Biology of Chameleons |pages= 7–55 |publisher= University of California Press |place=Berkeley, CA |year= 2014 |isbn=9780520276055}}</ref> The hyoid bone has an elongated, parallel-sided projection, called the entoglossal process, over which a tubular muscle, the accelerator muscle, sits.<ref name="Anderson et al. 2012"/><ref name="Anderson and Higham 2014"/><ref name="Herrel et al. 2001"/><ref name="de Groot & van Leeuwen 2004"/> 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.<ref name="Higham and Anderson 2014"/><ref name="Anderson et al. 2012"/><ref name="Herrel et al. 2001"/><ref name="de Groot & van Leeuwen 2004"/> 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.<ref name="Higham and Anderson 2014"/><ref name="Anderson et al. 2012"/><ref name="Anderson and Higham 2014"/><ref name="Herrel et al. 2001"/>

Tongue projection occurs at extremely high performance, reaching the prey in as little as 0.07 seconds,<ref name="Herrel et al. 2001"/><ref name="de Groot & van Leeuwen 2004"/><ref name="Anderson & Deban 2010">{{cite journal |doi=10.1073/pnas.0910778107 |title= Ballistic tongue projection in chameleons maintains high performance at low temperature |author1=Anderson, C. V. |author2=Deban, S. M. |journal=Proceedings of the National Academy of Sciences of the United States of America |year=2010 |volume=107 |issue= 12 |pages=5495–5499|bibcode= 2010PNAS..107.5495A |pmid=20212130 |pmc=2851764|doi-access= free }}</ref> having been launched at accelerations exceeding 41 [[G force|''g'']].<ref name="Anderson & Deban 2010"/> The [[Power (physics)|power]] with which the tongue is launched, known to exceed 3000 W kg<sup>−1</sup>, exceeds that which muscle is able to produce, indicating the presence of an elastic power amplifier to power tongue projection.<ref name="de Groot & van Leeuwen 2004"/> 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.<ref name="Anderson & Deban 2010"/><ref name="Anderson & Deban 2012">{{cite journal |doi=10.1242/jeb.078881 |title= Thermal effects on motor control and ''in vitro'' muscle dynamics of the ballistic tongue apparatus in chameleons |author1=Anderson, C. V. |author2=Deban, S. M. |journal=Journal of Experimental Biology |year=2012 |volume=215 |issue= 24 |pages=4345–4357 |pmid=23125336|doi-access=free }}</ref> While other [[Ectotherm|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.<ref name="Anderson & Deban 2010"/><ref name="Anderson & Deban 2012"/> 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.<ref name="Herrel et al. 2000">{{cite journal |title=The mechanics of prey prehension in chameleons |author=Herrel, A. |author2=Meyers, J. J. |author3=Aerts, P. |author4=Nishikawa, K. C. |journal=Journal of Experimental Biology |year=2000 |volume=203 |issue=Pt 21 |pages=3255–3263 |doi=10.1242/jeb.203.21.3255 |url=http://www2.nau.edu/froggy-p/pdfs/Herrel%20et%20al.%202000.pdf |pmid=11023845 |access-date=2014-11-16 |archive-date=2010-06-20 |archive-url=https://web.archive.org/web/20100620023301/http://www2.nau.edu/froggy-p/pdfs/Herrel%20et%20al.%202000.pdf |url-status=dead }}</ref> 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 temporarily expanding their thermal [[Ecological niche|niche]] as a result.<ref name="Anderson & Deban 2010"/>

<gallery mode="packed" heights="140px" caption="Use of tongue in feeding">
File:Chameleon gab fbi.png|Tongue structure, with cup-like end
File:Chameleon-Stage 04.jpg|Tongue begins strike
File:Chameleon-Stage 03.jpg|Capturing prey
File: Chameleon-Stage 01.jpg|Bringing prey to the mouth
</gallery>

=== Bones ===
Certain species of chameleons have bones that glow when under [[ultraviolet light]], also known as [[Biogenic substance|biogenic]] [[fluorescence]].<ref name="Prötzel et al 2018">{{Cite journal |last1=Prötzel |first1=David |last2=Heß |first2=Martin |last3=Scherz |first3=Mark D. |last4=Schwager |first4=Martina|last5=Padje |first5=Anouk van't |last6=Glaw |first6=Frank |display-authors=3|date=15 January 2018 |title=Widespread bone-based fluorescence in chameleons |journal=Scientific Reports |volume=8 |issue=1 |pages=698 |doi=10.1038/s41598-017-19070-7 |pmid=29335580 |pmc=5768862 |issn=2045-2322 |bibcode=2018NatSR...8..698P}}</ref> Some 31 different species of ''Calumma'' chameleons, all native to [[Madagascar]], displayed this fluorescence in [[CT scan]]s.<ref name=":1">{{cite magazine|url=https://news.nationalgeographic.com/2018/01/chameleon-bones-florescent-ultraviolet-light-spd/|archive-url=https://web.archive.org/web/20180118173045/https://news.nationalgeographic.com/2018/01/chameleon-bones-florescent-ultraviolet-light-spd/|url-status=dead|archive-date=January 18, 2018|author=Elaina Zachos|title=Chameleon Bones Glow in the Dark, Even Through Skin|magazine=National Geographic|date=2018-01-18|access-date=2018-08-03}}</ref> The bones emitted a bright blue glow and could even shine through the chameleon's four layers of skin.<ref name=":1" /> The face was found to have a different glow, appearing as dots otherwise known as [[tubercle]]s on facial bones.<ref name="Prötzel et al 2018" /> The glow results from [[protein]]s, [[Biological pigment|pigments]], [[chitin]], and other materials that make up a chameleon's skeleton,<ref name="Prötzel et al 2018" /> possibly giving chameleons a secondary signaling system that does not interfere with their colour-changing ability, and may have evolved from [[sexual selection]].<ref name="Prötzel et al 2018" />