Chameleon - Kamereon (English spelling) chameleon

Japanese: カメレオン - かめれおん（英語表記）chameleon

A general term for lizards belonging to the Chamaeleonidae family of the Squamata order of the Reptilia class. Members of this family, Chamaeleonidae, have many morphological characteristics. There are 70 species in the Chamaeleo genus and 16 species in the Brookesia genus, with half of them distributed across most of Africa except for the Sahara Desert and the island of Madagascar. Only one species, the Mediterranean chameleon C. chamaeleon , is found in southern Spain, North Africa, the Arabian Peninsula, India, and Sri Lanka, and is divided into four subspecies.

[Takahiro Matsui]

form

All species are morphologically similar, with a total length of 20 to 30 cm, and a tail slightly longer than half that length, but the Parson's chameleon C. parsonii and the Madagascar giant chameleon C. oustaleti , found in Madagascar, are large species that can reach a total length of 60 cm, while the dwarf chameleon B. nasus is only 3 to 4 cm long. Chameleons are thought to have evolved from the Agamidae lineage, and are the lizards most adapted to arboreal life. The body is significantly compressed laterally, and is supported by four limbs that extend diagonally downward from the shoulder girdle, and the inside is supported by thick ribs. On both the front and back legs, the five fingers are fused into two bundles of two and three, which face each other and allow the animal to grip branches firmly. The forelimbs have two fingers on the outside and three on the inside, while the hind legs are reversed, and the free fingertips have sharp claws. The tip of the tail wraps around a branch, but usually wraps vertically. The head is large and angular, with a bony helmet-like protuberance and horn-like projection. Male Jackson's Chameleons (C. jacksonii) have three horns at the tip of their snouts, while Fischer's Chameleons (C. fischeri) have a pair of horn-like projections. Many species also have a row of ornamental scales along the midline of the dorsal and ventral surfaces of the body. The upper and lower eyelids of the eyes are fused together in a dome shape and covered with fine scales, with a small hole at the apex that allows them to rotate separately to look in different directions.

[Takahiro Matsui]

Ecology

Chameleons are diurnal, mostly arboreal, but some also descend to the ground. Although their movements are extremely slow, they can walk on a single thin branch by lifting their body with their limbs. When they find insects or spiders to feed on, they focus with both eyes, wrap their tail around the branch, and shoot out their tongue while recoiling. The tongue is made up of a bundle of circular muscles and long, thin muscles, and is usually compressed and stored in the mouth. To shoot out the tongue, the animal first protrudes the inverted V-shaped hyoid bone in which the tongue is stored, tightens the circular muscles, and then suddenly relaxes them, so that the sticky tip hits the prey in a fraction of a second. Chameleons are also known for their skillful body color change, which can change rapidly not only depending on the environment, but also on emotions such as changes in light and dark, temperature, and fights between males during the breeding season. Most species are oviparous, digging holes in the ground and laying around 20 to 50 eggs, but some species are ovoviviparous.

[Takahiro Matsui]

Mela Chameleon
Genus Chameleon Smithsonian Institution (Jennifer Zoon) ">

Mela Chameleon

Major types of lizards (1) [specimen illustrations]
©Takahiro Matsui ">

Major types of lizards (1) [specimen illustrations]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

爬虫(はちゅう)綱有鱗目(ゆうりんもく)カメレオン科に属するトカゲの総称。この科Chamaeleonidaeの仲間は形態的に多くの特徴をもつ。カメレオン属Chamaeleo70種、コノハカメレオン属Brookesia16種が、サハラ砂漠を除くアフリカの大部分とマダガスカル島とにほぼ半数ずつ分布し、チチュウカイカメレオンC. chamaeleon1種のみがスペイン南部、北アフリカ、アラビア半島、インド、スリランカに分布し、4亜種に分けられている。

［松井孝爾］

形態

すべての種が形態的に類似し、全長20～30センチメートル、尾はその2分の1よりやや長いが、マダガスカル島産のパースンカメレオンC. parsoniiやマダガスカルオオカメレオンC. oustaletiは全長60センチメートルに達する大形種であり、他方、ヒメカメレオンB. nasusなどは全長3～4センチメートルにすぎない。カメレオンはアガマ科Agamidae系統から分化したと考えられ、トカゲではもっとも樹上生活に適応した形態をしている。胴は著しく側扁(そくへん)し、肩帯から斜め下方に張り出した四肢で支えられ、内部を太い肋骨(ろっこつ)で支えられる。前後肢ともに、5本の指は2本と3本の2束に癒合し、向かい合って枝を強く握ることができる。指は前肢では外側に2本、内側に3本、後肢ではその逆になっており、遊離した指先には鋭いつめがある。尾の先端部は枝に巻き付くが、通常は垂直方向に巻いている。頭部は大きくて角張り、骨質の兜(かぶと)状隆起や角(つの)状突起がある。ジャクソンカメレオンC. jacksoniiの雄は吻端(ふんたん)に3本、フィッシャーカメレオンC. fischeriは1対の角状突起をもつ。また胴の背面と腹面の正中線上に飾り鱗(うろこ)が並ぶ種類も多い。目は、上下の眼瞼(がんけん)がドーム状に癒着して細鱗に覆われ、頂点に小孔が開き、左右別々に回転して異なった方向を見ることができる。

［松井孝爾］

生態

カメレオンは昼行性で、大半が樹上性であり、一部が地上にも降りる。行動はきわめてのろいが、細い1本の枝の上でも四肢で胴を持ち上げながら歩ける。餌(えさ)の昆虫、クモ類をみつけると、左右の目で焦点をあわせ、尾で枝を巻き体に反動をつけながら、舌を発射する。舌は環状の筋肉の束と細長い筋肉からなり、通常は圧縮して口内に収められている。舌の射出は、まず舌が収まった逆V字形をした舌骨を突き出し、環状の筋肉を引き締め、急に緩めることで行われ、数分の1秒というスピードで粘着力のある先端部が獲物に命中する。また、カメレオンは巧みな体色変化で知られるが、体色は環境ばかりでなく明暗や温度の変化、繁殖期の雄の争いなど感情によってもめまぐるしく変化する。大半の種が卵生で、地上に穴を掘り20～50個ほどを産卵するが、一部の種では卵胎生である。

［松井孝爾］

メラ―カメレオン
　カメレオン属スミソニアン協会（Jennifer Zoon）">

メラ―カメレオン

トカゲのおもな種類(1)〔標本画〕

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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