And from the exciting world of marine biology, scientists think evolution has given giant squids excellent eyesight.

The streamlined giant squid (various species of Architeuthis) and the much chunkier colossal squid (Mesonychoteuthis hamiltoni) can both grow to more than 10m long, as measured from the tip of the body to the end of their tentacles.

The colossal squid especially is equipped with a fearsome arsenal of weapons, including barbed swivelling hooks.

Scars on whale believed to have been caused by Giant Squids

Scars on the bodies of sperm whales indicate that they regularly do battle with the colossal squid, at least in the Southern Hemisphere waters where it lives.

And the number of colossal squid beaks found in the stomachs of sperm whales indicate that the latter often win.

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.

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.


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