The colossal squid has the largest eye of any animal

Deep in the Southern Ocean lives an animal with the biggest eyes ever measured. The colossal squid (Mesonychoteuthis hamiltoni) has an eye roughly 27 centimetres across — about the size of a soccer ball — with a lens the size of an orange.

That is almost certainly the largest eye in the history of the animal kingdom. The eye drinks in light at depths near 1,000 metres, where sunlight effectively never reaches; by collecting nearly every available photon, the squid can pick out faint movement in the black — including the shadow of an approaching sperm whale, its main predator.

The colossal squid also wins on bulk: at up to 450 kilograms it is likely the heaviest invertebrate alive. Its better-known cousin, the giant squid, is longer — up to 12–14 metres tip to tip — but lighter, and its dinner-plate eyes sit on the sides of its head rather than facing forward.