The common cuttlefish is the largest of the three cuttlefish species found in UK waters. (Over 120 species are found world-wide) The common has eight arms, two elongated tentacles and a mantle (a hood made of muscle and skin that covers the body). It also has a pair of flat, wide fins (like a skirt) that encompasses their entire mantle. Within its body, the cuttlefish has an oval internal shell, the cuttlebone. It feeds mostly on shrimp and crabs.

The common cuttlefish is a cephalopod, a group of marine invertebrates that includes squid and octopus. Like its relatives it is highly intelligent, with one of the largest brain-to-body ratios of all invertebrates. Studies found that cuttlefish are able to count and pass a test of self-control. The cuttlefish ignored food if it knew that a tastier treat was on the cards later, in this instance shrimp.

Alongside its intelligence, the common cuttlefish has the remarkable ability to change the colours and brightness of its skin. Its skin is adorned with specialized pigment cells called chromatophores, which allow it to change colour rapidly, changing from mottled brown to vibrant blues and greens in an instant.

It uses this talent to both camouflage itself into its surroundings as well as put on dazzling displays to attract mates and hypnotise potential prey. The common cuttlefish has been observed camouflaging itself on one side of its body to hide from predators, whilst displaying mesmerising, flashing patterns and colours on the other to attract a mate. The males have also been observed mimicking a female to hide from more dominant males and get closer to a potential mate without alerting them.

When threatened, the cuttlefish squirts ink. Just like squid and octopuses, it releases a cloud of dark ink into the water, confusing predators and providing cover for its getaway. During its escape, the cuttlefish can also propel itself backward using a siphon, propelling it away from danger with a form of jet propulsion. The colour sepia is named after the common cuttlefish (Sepia officinalis) and the redish-brown ink it expels.

There is much more to uncover about the common cuttlefish including its specialised vision and uses for its cuttlebone. To find out more, click here.

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