Ryan Photographic - Anablepidae - Four-eyed fishes

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Family Anablepidae

According to FishBase there are 9 species of the Anablepidae in 3 genera.

Four-eyed fishes don't actually have four eyes but they might as well have. Each eye is split in two by a bar of tissue and the upper and lower portions of the eye have separate pupils. The lens is ovoid rather than spherical and the light path through it becomes longer in the underwater portion. Four-eyed fishes usually swim with the top part of the eye (the "above water eye") out of the water, the skin partition at the meniscus, and the underwater portion - underwater. They have excellent all round vision and can see prey or predators both above and below water.

The Anablepidae are live bearers. Like guppies they possess a modified anal fin, the gonopodium, with which they inseminate the females. But life isn't easy for male four-eyed fishes. Males are either left or right "gonopodiumed" - sinistral or dextral. Females have a vent that either slopes to the left or the right. The end result is that males with a left rotating gonopodium can only mate with right-handed females and vice-versa for right gonopodiumed males. Not surprisingly my spellchecker does not recognize "gonopodiumed" and I think I just coined the phrase. The genetics of this would be a fascinating study for some postgrad student. Will the two populations speciate?

The family mostly lives in fresh or brackish water along the coast of southern Mexico to Northern South America (FishBase says southern South America but I suspect this is a mistake - repeated by Wikipedia), only rarely are they encountered in the sea. As they often prey on insects this is not surprising.

Anableps anableps Four-eyed fish

four-eyed fish Anableps

Anableps anableps Four-eyed fish head shot, eyes half in and out of water. Captive, Denver Zoo (image is a collage).

Anableps, four-eyed fish eyes above water

Four-eyed fish eyes above water

Anableps species viewed from above

FISH 8262 Anableps species captive, Fort Worth Zoo.







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