rerun from live journal
The four-eyed fish (anableps anableps) is an unusual South American live bearer with two pupils in each eye. Both of its pupils are connected to the same iris but the thickness of their lens vary quite a bit. One pupil is well adapted to see above the surface of the water and the other below the surface. The fish can process both inputs at once. Four-eyed fish spend most of their time at the surface of the water and tend to hang out in schools. They are not unheard of as aquarium fish and tend to do well with un-aggressive brackish species.