Giant and colossal squids have eyes as big as basketballs to spot and escape from sperm whales, according to a new study.
Researchers from Duke University have found that giant squids have huge eyes to spot their predators. They discovered this when they analsyed the squids' eyes. The team found that the design and size of the eye give squids the ability to see approaching sperm whales as they disturb bioluminescent organisms.
Big squids come in two types - giant and colossal. They can grow to weights of five adult men put together, which is comparable to a large swordfish. But swordfish eyes are about the size of softballs, about 3 inches in diameter.
"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," said Sonke Johnsen, biologist from Duke University. "The question is why. Why do giant squid need such large eyes?"
To find out why the squids' eyes are huge, the researchers first measured giant and colossal squid eyes using photos and captured animals. They found that the squids' large eyes collect more light compared to animals of similar size but with smaller eyes. The extra light intake improves the squid's ability to detect small contrast differences under the dim conditions of the deep ocean. This is the main reason they have got such huge eyes.
"They're most likely using their huge eyes to spot and escape their predators, sperm whales," said Johnsen.