My, Mr. Squid, what a big eye you have! Oh, and a little one, too? That's a little weird.
The cock-eyed squid's mismatched eyes — it has one regular-sized eye and a large, yellow-colored one — have been something of a mystery to marine researchers, but thanks to new observational studies, we may finally know the reason thanks to a study published recently in Philosophical Transactions of the Royal Society B.
Living between 656 and 3,280 feet down in the ocean, the cock-eyed squid doesn't have much exposure to light, but it uses its separate eyes to differentiate between types of light, the real kind and the bioluminescent light given off by its prey.
The squid's regular-sized eye is always pointing down to the ocean floor to spot any glowing prey, like lanternfish or shrimp. They light up well against the inky blackness of the ocean, so that eye doesn't need a great deal of visual acuity. The large, yellow eye, however, may be able to distinguishing between any natural sunlight that may be filtering down into the ocean and the bioluminescence emitted by any prey above it.
Basically, no matter where its prey swims, the cock-eyed squid has at least one eye on it at all times.