Which animal has the largest eyeball in the world?
And the answer: the giant squid.
The giant squid has the largest eyeball in the animal kingdom. More than 25 centimeters in diameter, the squid's eyeball is about the size of a dinner plate, or as big as a human head. Scientists believe the large eyes help the squid recognize large shapes of predators moving in the water, like the sperm whale.
If you thought whales were the only massive creatures inhabiting the depths of our seas, you might have to strap in for this one. The aptly named giant squid is the largest invertebrate on Earth, though, curiously, the most elusive. These sea creatures dwell exclusively in the deepest parts of the ocean, making it incredibly difficult for researchers to learn more about their species or observe them in their natural habitats. In fact, most of what we know of these squid comes from those that have washed ashore or been accidentally hauled in by fishermen.
That is, until 2004, when researchers in Japan took the first ever photos of the giant squid. And, in 2006, scientists with Japan's National Science Museum managed to surface a 24-foot female giant squid (though that might seem frighteningly big, the largest of these giants ever to be measured clocked in at a staggering 59 feet long).
Giant squid have some of the most unique qualities of any animal on the planet, land or sea. Their massive eyes allow them to seek light and make sense of their surroundings in the lightless depths of the ocean, with water-filled retinas that deflate in air. Meanwhile, their diet consists of anything from shrimp to, it's believed, small whales (yes, you read that right). Giant squid are also equipped with long tentacles that are twice their body length, allowing their grip to shoot out far and wide to catch prey.
Scared yet? Us too. Learn more about giant squid here.