The four eyed fish

In Central and South America there's a fish which has four pupils (technically only two eyes, I kinda lied in the title)! Inside each eye one pupil detects light from above and one from the sides and below. The purpose of the pupils detecting light from above being to see things above the surface of the water in clearer vision, aided by the fact that the lenses directing light into the top pupils protrude out of the water! Every once in a while the fish has to dip these eyes below the surface, presumably to keep the eyes moist!

The iris of each eye doesn't make up one circular pupil like ours but is squashed together in the centre, making two separate holes for light to shine through onto the retina presumably onto two different focal points so the brain can distinguish between the underwater and out-of-water images.

Another interesting fact about this fish is that the genitalia of both male and female are variable as to which side of the fishes body they are found! Meaning males can only mate with a female with corresponding genitalia location!