Sensitive squid eyes a defence against whales

An ARMS race in the ocean depths may have led giant squid to evolve their enormous eyes, say scientists.

A study suggests the huge eyes are designed to provide early warning of the squid’s mortal enemy, the sperm whale.

Squid are deaf to the acoustic “pinging” signals of the whales’ sonar, but have developed an effective form of defence – super-sensitive eyes, scientists believe.

The eyes can pick up tiny contrast differences in the darkness of the deep ocean. They would allow the squid to see the tell-tale bioluminescence of an approaching sperm whale from around 120 metres.

Wake produced by the whales triggers small plankton organisms to generate light. Although the glow is faint because of absorption and scattering of the water, it can be seen from an appreciable distance by a pair of large enough eyes.

The US authors of the new research measured giant squid eyes using photos and captured animals.