Fish Able to See Above and Below Water

http://www.scientificamerican.com/podcast/episode.cfm?id=bifocal-fish-sees-differently-above-11-07-20&WT.mc_id=SA_facebook

A fish (Anableps anableps) that keeps its eyes half submerged has specially adapted pupils and retinas to see clearly both above and below the water. It lives in the brackish waters of mangrove swamps in central and South America, and hunts for food at the water's surface... its bulging eyes submerged halfway. Each eye has two pupils, one above water, one below. And each pupil sends incoming visual info to a different side of the fish's retina. Cones in each half of the retina are adapted to produce different light-filtering pigments. So cones hit by underwater rays are primed to sense longer-wavelength yellow light. Cones hit by daylight are sensitive to shorter-wavelength green light. The entire arrangement makes it easy for this bifocal fish to spot a tasty bug flying above the water, or a bit of algae below.

Wouldn't it be interesting to have two pupils for each eye? Being able to see above and below water at the same time? These kinds of adaptations seem rare in the animal kingdom.