Four-eyed fish
The four-eyed fishes are a genus, Anableps, of fishes in the family Anablepidae. They have eyes raised above the top of the head and divided in two different parts, so that they can see below and above the water surface at the same time. The optomotor response or OMR has been used as a test to investigate potential differential visual processing in Anableps on normal versus ‘blinded’ fish (the eyes are actually covered—not physically blinded). It was found that the OMR does exist in Anableps and that the strength of this response is dependent on the visual field being tested—a stronger OMR was seen as a result of visual stimulation from the aerial environment. Like their relatives, the onesided livebearers, four-eyed fishes mate only on one side, right-"handed" males with left-"handed" females and vice versa. These fish inhabit fresh and brackish water and are only rarely coastal marine. They originate in lowlands in southern Mexico to Honduras and northern South America. Species There are currently three recognized species in this genus: Anableps anableps (Linnaeus, 1758) (Largescale foureyes) Anableps dowei T. N. Gill, 1861 (Pacific foureyed fish) Anableps microlepis J. P. Müller & Troschel, 1844 (Foureyes) Physical characteristics The maximum length