- The pupils in squid's dinner-plate-sized eyes are 3.5 inches (9 cm) across.
- The size of their eyes allows squid to see tiny sparks of bioluminescence at a distance.
The enormous eyes of giant and colossal squid may help them spot predatory sperm whales in their dim undersea habitat, a new study finds.
These mysterious squid are tough to spot and even tougher to study in their natural habitat. But squid that have been caught or observed have huge, basketball-size peepers - three times the diameter of another other animal, including behemoths of similar size, such as swordfish.
"It doesn't make sense a giant squid and swordfish are similar in size, but the squid's eyes are proportionally much larger, three times the diameter and 27 times the volume," study researcher Sönke Johnsen, a biologist at Duke University, said in a statement. "The question is why. Why do giant squid need such large eyes?"
To find out, Johnsen and her colleagues first had to confirm the eye size of these elusive creatures, because most eye size reports were based on anecdotes. They obtained photographs of the eye of a freshly caught giant squid and were able examine the corpse of a colossal squid, an even larger species, from New Zealand. (Gallery: Stunning Squid)