Squids' giant eyes seen as defense aid

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DURHAM, N.C., March 15 (UPI) -- Giant squid have giant eyes -- among the biggest in nature -- for defending themselves from sperm whales, their biggest enemy, a U.S. researcher says.

"They're most likely using their huge eyes to spot and escape their predators, sperm whales," Duke University biologist Sonke Johnsen says of the animals' basketball-sized orbs.

Johnsen was part of a team that modeled, both physically and biologically, how and why a squid uses such a big eye, and found the design and size of the eye give squid the ability to see approaching sperm whales as they disturb bioluminescent organisms in deep ocean waters, a Duke release reported Thursday.

The team found the large eyes collect more light compared to animals of similar size but with smaller eyes.

That's critical for detecting low light differences such as the bioluminescence stimulated by large animals such as approaching sperm whales, Johnsen said.

Bigger eyes mean seeing more of the faint light and predicting the predator's approach, she said.

"It's the predation by large, toothed whales that has driven the evolution of gigantism in the eyes of these squid," Johnsen said.