Manatee - Manatee (English spelling)

A general term for aquatic animals belonging to the order Sirenia and family Manateidae of the class Mammalia. Three species of this family, Trichechidae, currently exist in the tropical and subtropical regions of the Atlantic coast. The American manatee, Trichechus manatus, lives in coastal areas from the West Indies to the Gulf of Mexico and the Guiana region, and is a large species that can reach a body length of 3.3 meters and a weight of 500 kilograms. The African manatee, T. senegalensis, lives on the west coast of Africa from Senegal to Angola, and is similar in appearance to the American manatee. These two species are found in rivers, estuaries, and seawater. The Amazonian manatee, T. inunguis, lives only in the Amazon waters and does not migrate to the sea. It is a small species that reaches a body length of about 2.3 meters and weighs about 200 kilograms.

Manatees share the same ancestors as elephants, and lived on land in the Eocene epoch of the Tertiary Period, but are said to have migrated to the water to escape predators. Their bodies are spindle-shaped and somewhat flattened, which is suited to underwater life. Their forelimbs become somewhat long pectoral fins, which they use to hold food between their left and right hands and carry it to their mouths. They have no hind limbs. Their tail fin is large and oval, like a rice scoop, and they swim slowly by swinging it up and down. Their eyes are small and their eyesight is poor. They have no external ears, but their inner ears are well developed. Their heads are small and have well-developed upper lips with thick tentacles around them that they use to select food. Their bodies are sparsely covered with fine hairs. They have six cervical vertebrae, one less than most mammals. They are herbivores, feeding on mangroves, aquatic plants, and water hyacinth near the water. They are generally nocturnal and docile in nature. Due to overfishing for its meat, its population has decreased, and it is now protected by the Washington Convention. A closely related species is the marine dugong, which is said to have been the model for the mermaid legend.

[Sonoda Seizaburou]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

哺乳(ほにゅう)綱海牛目マナティー科に属する水生動物の総称。この科Trichechidaeの仲間は、大西洋沿岸の熱帯・亜熱帯域に1属3種が現存する。アメリカマナティーTrichechus manatusは、西インド諸島からメキシコ湾、ギアナ地方にかけての沿岸部に生息し、体長3.3メートル、体重500キログラムに達する大形種である。アフリカマナティーT. senegalensisは、アフリカ西岸のセネガルからアンゴラにかけて生息し、形態はアメリカマナティーに似ている。以上の2種は河川、河口、海水域ともにみかけられる。アマゾンマナティーT. inunguisは、アマゾン水系にのみ生息し、海に移ることはない。体長2.3メートル、体重200キログラム程度の小形種である。

　マナティーは祖先をゾウと同じくし、第三紀始新世には陸上生活を営んでいたが、外敵を逃れて水中に移りすんだといわれる。体は水中生活に適した紡錘形でやや扁平(へんぺい)。前肢は胸びれとなりやや長く、左右で餌(えさ)を挟み口まで運ぶ。後肢はない。尾びれは大きくしゃもじ状の長円形で、これを上下にあおりゆっくりと泳ぐ。目は小さく、視力は弱い。外耳はなく、内耳は発達している。頭部は小さく、よく発達した上唇をもち、その周辺に太い触毛があり、これで餌を選別する。全身にまばらに細毛がある。頸椎(けいつい)骨は多くの哺乳類より1個少なく6個である。草食獣で、水辺のマングローブや水草、ホテイアオイを採食する。一般に夜行性で、性質はおとなしい。食肉の目的で乱獲され減少したため、現在はワシントン条約によって保護されている。近縁種には海産のジュゴンがあり、この種は人魚伝説のモデルとなったといわれる。

［園田成三郎］

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