How big are the eyes of the world’s largest squid? Try bigger than a regulation NBA basketball.
In fact, they offer just one advantage: they can spot enormous shapes – such as those of their arch-foe, the sperm whale, according to the BBC.
Think of it as a cephalopod early warning system.
Scientists found that the huge eyes, two to three times bigger than any other animal’s, offer no advantages in the murky ocean depths other than making it easier to spot enormous shapes – such as sperm whales.
Scientist Dan Nilsson from Lund University in Sweden was on hand for the dissection of a colossal squid four years ago in New Zealand.
He was able to examine and handle the eyes – in particular, the hard parts of the lens.
These alone are bigger than an entire human eye, the BBC reported.
“We were puzzled initially, because there were no other eyes in the same size range – you can find everything up to the size of an orange, which are in large swordfish,” Nilsson told the BBC.
“So you find every small size, then there’s a huge gap, then there are these two species where the eye is three times as big – even though squid are not the largest animals.”
Nilsson’s team’s models revealed that, what the colossal and giant squid’s supersize pupils and retinas lacked in close-up vision they made up for with extreme farsightedness, according to National Geographic.
“The cephalopods are fine-tuned to spot very large objects at a distance—such as the sperm whales that prey on the squid,” the magazine added.
The squid’s eye appears to be its only means of detecting sperm whales before the latter attack.
“Whereas the whales can spot squid using sonar, the squid can deploy nothing except vision – which suggests there would be a powerful evolutionary pressure towards developing effective eyes,” according to the BBC.
The colossal and giant squid eye study was published in the March 15 by the journal Current Biology.
The streamlined giant squid can grow up to 33 feet long while the much chunkier colossal squid can grow to 45 feet, as measured from the tip of the body to the end of their tentacles.
The colossal squid is an elusive beast. The first specimen wasn’t taken by man until 1981. It is equipped with an arsenal of weapons, including barbed swiveling hooks.
Giants squids, on the other hand, have been documented as long ago as the fourth century B.C.
Scars on the bodies of sperm whales indicate that they do battle with giant squids regularly, and colossal squid beaks found in the stomachs of sperm whales indicate that those two also pair off.
Though colossal squid are encountered remarkably rarely by people, they are thought to make up about three-quarters of sperm whales’ diet in the Southern Ocean.
(Above: Biologist Eric Warant of Sweden’s University of Lund holds lenses taken from the eyes of a colossal squid on April 30, 2008. Photo credit: National Geographic.)