Four-eyed fish - Yotsumeuo (English spelling)

A brackish-water fish belonging to the order Cypriniformes and family Pontedridae. It is also called Anableps by its genus name. It is found from the tropical parts of Central America to the northern coast of South America. It lives in coastal waters such as river mouths and mangrove areas, and sometimes invades fresh water. The eyes are located on the top of the head, and the cornea is divided horizontally into two parts by a strip of skin tissue, and it swims with the upper part above the water surface. Light entering from above and below the water surface separately passes through a single lens and forms separate images on the retina, which is also divided into two parts. It can reach a total length of 30 cm. The four-eyed fish is ovoviviparous, and the male's anal fin is modified into a thickened rod-like copulatory organ. The larvae are 3 to 4 cm long. The genus Anableps, which includes this species, includes A. microlepis , which has a distribution area almost the same as that of the four-eyed fish, and A. dovii , which is found only in Central America.

[Taki Yasuhiko]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

硬骨魚綱メダカ目ヨツメウオ科に属する汽水魚。属名でアナブレプスともよばれる。中央アメリカ熱帯部から南アメリカの北岸に分布。河口、マングローブ帯などの沿岸水域に生息し、ときには淡水中に侵入する。目は頭部上面に位置し、角膜が帯状の皮膚組織で水平に上下2部に仕切られており、上部を水面上に出して遊泳する。水面上と水中から別々に入った光は1個のレンズを通り、やはり2部に分かれた網膜に別々に像を結ぶ。全長30センチメートルに達する。ヨツメウオは卵胎生で、雄の臀(しり)びれは肥厚した棒状の交尾器に変形している。産出される仔魚(しぎょ)は全長3～4センチメートル。本種を含むアナブレプス属には、分布域がヨツメウオとほとんど同じであるミクロレピスA. microlepisと中央アメリカにのみに分布するドビーA. doviiがある。

［多紀保彦］

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