Why do colossal squids have such colossal eyeballs? (+video)
The colossal squid is thought to have the largest eyes of any animal. A new study suggests that the squids eyes evolved to help them avoid sperm whales.
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?"
Where'd you get those peepers?
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]
The examinations confirmed the squid eyes can get up to 10.6 inches (27 centimeters) in diameter. The pupils in these dinner-plate-size orbs are 3.5 inches (9 cm) across.