Four-eyed fishes(Anableps spp.) only has two eyes, but each pupil has an opaque partition that runs horizontally across it, making it , as its name suggests.
ヨツメウオは目が2つしかありませんが、それぞれの瞳を水平に横切る不透明の仕切りがあり、名前のとおり目が4つあるように見えます。
Four-eyed fishes are surface dwellers and have eyes adapted for seeing both above and below the water surface. The eyes are on top of the head, and each is divided into two parts, an upper half for vision in air, and a lower half for vision in water
1個の眼球にレンズは1個ですが、像に映る網膜は上下２ヶ所に分かれています。ヨツメウオはこの目の構造により、水面上と水中を同時に見ることができます。カエルのように目を水面上に出し上の目は水上を水鳥などの敵に注意し、下の目は水中を見獲物を探しながらユラユラと泳ぎます。
Four-eyed fishes grow to a maximum length of about 30 centimetres (one foot), found in the Amazon water system. Tropical fish that are easy to care for and can be found at tropical fish stores.
アマゾン水系にいる15㎝（最大で30cm）くらいのメダカの仲間。水族館 熱帯魚屋さんでも見られる飼育がやさしい熱帯魚。
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