OCTOPUS, SQUID, NAUTILUS AND CUTTLEFISH - THE INCREDIBLE CEPHALOPOD FAMILY!

They've got blue blood, three hearts, can change shape, use jet-propulsion and have inspired myths and legends since the dawn of time.

The word cephalopod means 'head foot' as they all have their feet growing straight out of their heads! The cephalopod family, whose members include octopus, nautilus and cuttlefish are surely among the planet's most bizarre inhabitants.

There are approximately 650 different species ranging from the tiny 5cm long Sepiola to the monstrous Architeuthis - or Giant Squid - which can reach lengths in excess of 18 metres!

Despite being closely related to the garden slug some members of the cephalopod family are believed to be as intelligent as pet dogs and can solve complex puzzles.

Most cephalopods can rapidly change body shape, texture and colour. It's believed that some species use this ability to communicate basic emotions - like fear and anger.

Octopus are also the undisputed kings of underwater escapology. With no skeleton they can squeeze their bodies through the tiniest of gaps - during tests one 60 pound specimen in America escaped through a two inch hole!

They can also change colour to match their surroundings so effectively that it's almost as if they've become invisible. 

When all else fails, octopus produce their very own 'smoke screens' or body doubles made out of ink to confuse attackers.

Cephalopods are molluscs and related to bivalves like scallops, oysters and clams as well as gastropods like slugs and snails.

Like snails, nautilus still have an external shell which they fill with gas to control their buoyancy.

However some cephalopods, including Squid and Cuttlefish, through millions of years of evolution now have their shells inside their bodies.

The deadliest cephalopods are not Giant Squid but a group known as Blue-ringed octopuses. There are at least 10 species, the largest of which only grows to 10 inches in diameter. 

What it lacks in size, however, it more than makes up for in potency - with a venomous bite containing enough poison to kill a full grown adult in 90 minutes.