Creatures

Nine animals, chosen because each one does something unexpected. Sizes are typical upper figures, not records, unless stated.

North Atlantic right whale

Eubalaena glacialis

A baleen whale that feeds on tiny copepods by skimming with its mouth open. It was hunted close to extinction, and ship strikes and fishing gear remain the main dangers.

Up to about 16 m long. Only a few hundred remain.

CoastalCritically endangered

Atlantic bluefin tuna

Thunnus thynnus

Built for speed and distance. It keeps its swimming muscles warmer than the surrounding water, which lets it hunt in cold seas and cross the ocean between feeding and spawning grounds.

Large adults exceed 3 m and several hundred kilograms.

Open oceanMigratory

Greenland shark

Somniosus microcephalus

It swims slowly, grows about a centimetre a year, and matures late. A 2016 study estimated the oldest animal sampled at roughly four centuries, with wide uncertainty.

Often 4 to 5 m long; found from the surface in the Arctic to well below 2,000 m.

Deep waterLong-lived

Lion's mane jellyfish

Cyanea capillata

The largest known jellyfish. Its tentacles trail behind the bell in a dense curtain, and small fish sometimes shelter among them.

Bells over 2 m across and tentacles longer than 30 m have been recorded.

Cold surface waterStings

Portuguese man o' war

Physalia physalis

A siphonophore: a floating colony in which different members handle feeding, defence and reproduction. The float acts as a sail, so whole fleets wash ashore after steady onshore wind.

Float up to about 30 cm; tentacles commonly around 10 m.

SurfaceStings

Common octopus

Octopus vulgaris

Three hearts, blue blood and a talent for problem-solving. It changes colour and skin texture in a fraction of a second and squeezes through any gap wider than its beak.

Lives only a year or two.

Reefs and rocky coast

Leatherback turtle

Dermochelys coriacea

The largest turtle and the only one without a hard shell. It crosses the Atlantic to feed on jellyfish in cool northern waters and dives deeper than 1,000 m.

Adults can reach 2 m and more than 500 kg.

Open oceanVulnerable

Atlantic horseshoe crab

Limulus polyphemus

Each spring it comes ashore in large numbers to spawn on the full and new moon tides, and its eggs feed migrating shorebirds. Its blue blood is used to test medicines for bacterial contamination.

A relative of spiders and scorpions, not a true crab.

ShallowsWestern Atlantic

Atlantic cod

Gadus morhua

The fish that fed Europe for centuries. Overfishing collapsed the stock off Newfoundland, and the fishery there was closed in 1992.

Lives near the bottom, usually shallower than 600 m.

Continental shelfCold water