Giant Squid

Architeuthis dux

The giant squid is the deep sea's most storied invertebrate, a mollusc built on an almost unimaginable scale. Females can reach roughly 12 to 13 m from the fins to the tips of the long feeding tentacles, though much of that length is slender arm and tentacle rather than bulk; the muscular mantle itself is only about 2 m. It carries among the largest eyes of any animal, up to around 27 cm across, an adaptation for gathering the faint glow and bioluminescent flashes of the deep. Its tissues are laced with an ammonium-rich fluid lighter than seawater, which keeps it neutrally buoyant and lets it hang almost weightless in the water column. Two elastic feeding tentacles, tipped with toothed, sucker-lined clubs, shoot out to grab fish and smaller squid and draw them back toward a sharp beak. The species is found in every ocean along continental and island slopes, usually between about 200 and 1,000 m, and is uncommon in tropical and polar waters. Its principal predator is the sperm whale, which frequently carries ring-shaped sucker scars from the struggle. Males pass sperm packets into the female's arms, and young juveniles occasionally drift up into surface waters. For most of history the animal was known only from carcasses and from beaks left in whale stomachs; the first images of a living giant squid in its natural habitat were taken off Japan in 2004, and in-situ footage like this remains exceedingly rare.