Chameleon 0.9 Crack Mac Osx
Elliott Davis
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]
In 1986, the family Chamaeleonidae was divided into two subfamilies, Brookesiinae and Chamaeleoninae.[10] Under this classification, Brookesiinae included the genera Brookesia and Rhampholeon, as well as the genera later split off from them (Palleon and Rieppeleon), while Chamaeleoninae included the genera Bradypodion, Calumma, Chamaeleo, Furcifer and Trioceros, as well as the genera later split off from them (Archaius, Nadzikambia and Kinyongia). Since that time, however, the validity of this subfamily designation has been the subject of much debate,[11] although most phylogenetic studies support the notion that the pygmy chameleons of the subfamily Brookesiinae are not a monophyletic group.[12][13][14][15]
Some chameleon species are able to change their skin coloration. Different chameleon species are able to vary their coloration and pattern through combinations of pink, blue, red, orange, green, black, brown, light blue, yellow, turquoise, and purple.[17] Chameleon skin has a superficial layer which contains pigments, and under the layer are cells with very small (nanoscale) guanine crystals. Chameleons change color by "actively tuning the photonic response of a lattice of small guanine nanocrystals in the s-iridophores".[18] This tuning, by an unknown molecular mechanism, changes the wavelength of light reflected off the crystals which changes the color of the skin. The color change was duplicated ex vivo by modifying the osmolarity of pieces of white skin.[18]
Color 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. Color change signals a chameleon's physiological condition and intentions to other chameleons.[19][20] Because chameleons are ectothermic, another reason why they change color is to regulate their body temperatures, either to a darker color to absorb light and heat to raise their temperature, or to a lighter color to reflect light and heat, thereby either stabilizing or lowering their body temperature.[21][22] Chameleons tend to show brighter colors when displaying aggression to other chameleons,[23] and darker colors 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 colors 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 color changes that are used for communication between chameleons have increased whereas anti-predator camouflage color changes have decreased relative to the native source population in Kenya where there are more predators.[28]
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 color which is common of many chameleons in their relaxed state. Chameleon color palettes have evolved through evolution and the environment. Chameleons living in the forest have a more defined and colorful palette compared to those living in the desert or savanna, which have more of a basic, brown, and charred palette.[30]
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 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 neonatal lizard preserved in the Cretaceous (Albian-Cenomanian boundary) amber from Myanmar. The authors noted that the lizard has "short and wide skull, large orbits, elongated and robust lingual process, frontal with parallel margins, incipient prefrontal boss, reduced vomers, absent retroarticular process, low presacral vertebral count (between 15 and 17) and extremely short, curled tail"; the authors considered these traits to be indicative of the lizard's affiliation with Chamaeleonidae. The phylogenetic analysis conducted by the authors indicated that the lizard was a stem-chamaeleonid.[34] However, Matsumoto & Evans (2018) reinterpreted this specimen as an albanerpetontid amphibian.[35] This specimen was given the name Yaksha perettii in 2020, and was noted to have several convergently chameleon-like features, including adaptations for ballistic feeding.[36]
While the exact evolutionary history of color change in chameleons is still unknown, there is one aspect of the evolutionary history of chameleon color 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 colors.[37]
Chameleons vary greatly in size and body structure, with maximum total lengths varying from 22 mm (0.87 in) in male Brookesia nana (one of the world's smallest reptiles) to 68.5 cm (27.0 in) in the male Furcifer oustaleti.[38][39] 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.
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.
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]
All chameleons are primarily insectivores that feed by ballistically projecting their long tongues from their mouths to capture prey located some distance away.[45] 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.[46] 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.[47]
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