Suffolk Wildlife Trust: Common cuttlefish

Common cuttlefish by R Spray
Common cuttlefish by R Spray
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In spite of its name, the common cuttlefish is actually a mollusc, belonging to the same class of animals as squid and octopuses.

In spite of its name, the common cuttlefish is actually a mollusc, belonging to the same class of animals as squid and octopuses.

They are the largest cuttlefish species, growing up to 49cm long, and are native to the North Sea and also the Mediterranean and Baltic Seas. Common cuttlefish are shallow water dwellers, preferring depths of up to 200m, and use sand or mud substrate as their spawning grounds.

Many of us are familiar with cuttlefish ‘bones’ which are occasionally seen washed up on beaches and also hung in budgie cages as a source of calcium. These ‘bones’ are actually internal shells which are porous to gas and air and used a buoyancy regulator. Cuttlefish also have eight arms and two tentacles covered in suckers for catching prey, and they produce a saliva containing neurotoxins. They feed on molluscs, fish, shrimps, worms, octopus and other cuttlefish which they sneak up on, and then capture by shooting out their two long tentacles ensnaring prey with strong suckers and pulling them into their beak-like mouth.

Tests have shown these molluscs are likely to be one of the most intelligent of all invertebrates, with the cuttlefish brain being huge in comparison to its body size. They also possess highly developed eyes which have W-shaped pupils which enable them to detect light polarisation and to see both backwards and forwards at the same time.

Another remarkable skill of these clever molluscs is the ability to change the colour of their skin. This is done by altering colour pigments in the skin surface and has led to them being known as ‘chameleons of the sea’. They change their colour to communicate to other cuttlefish and also as a brilliant means of camouflage when hunting.

Common cuttlefish predators include monkfish, swordfish, seals, dolphins and whales. Cuttlefish can also produce ink which they squirt into the seawater to confuse predators and give them a chance to get away. In the past cuttlefish ink was an important dye called sepia, which is where their scientific name, Sepia officinalis, originates. Sepia was used in the production of artists’ paint, but luckily for the cuttlefish, this has been replaced by a synthetic dye in modern times.

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