These intelligent animals, which are related to squid and octopuses, can change the colour, pattern, and texture of their skin to hide from predators, confuse other animals and communicate with other cuttlefish.
Cuttlefish live fast and die young. They usually only live for around two years and die after they’ve reproduced. The babies are fully independent as soon as they hatch – their parents don’t look after them or teach them how to swim, hunt or protect themselves. It’s a good thing they’re intelligent. These clever creatures can even exercise self-control – foregoing a delicious snack if they know they’ll be rewarded with a better one for waiting.
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What are cuttlefish?
Cuttlefish aren’t fish at all. They’re cephalopods, which means they’re related to squid and octopus. Squid, octopuses and cuttlefish all have three hearts, blue blood and a hard beak for chomping their prey but there are some key differences between them. While octopuses have eight arms, both squid and cuttlefish also have two long tentacles that extend even further than their arms. Cuttlefish also have a skirt-like fin that goes around the edge of their body and helps them swim. One easy way to tell the difference between a squid, octopus and cuttlefish? They have round, rectangular, and W-shaped pupils, respectively.
How many species of cuttlefish are there?
There are over 120 species of cuttlefish found in waters around the world, including in the UK.
How do cuttlefish see?
Cuttlefish experience the world around them very differently to us – they are colourblind but they can detect the angle at which polarised light bounces off a surface.
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Where do cuttlefish live?
There are over 120 species of cuttlefish living in tropical and temperate oceans around the world. The largest species – giant cuttlefish (Sepia apama) – is found in Australian waters while the smallest – the flamboyant cuttlefish (Metasepia pfefferi) – lives in the Indo-Pacific.
Common cuttlefish (Sepia officinalis) are found throughout UK waters year-round, particularly off the south and west coasts. Sometimes known as European cuttlefish, this species tends to live offshore but comes closer to our coastline to reproduce.
You might see clues that common cuttlefish are in UK waters while out on a beach walk. Cuttlefish eggs, which look like a bunch of black grapes, can sometimes be found washed up on the beach, as can their distinctive white, oval cuttlebone. Because these are rich in calcium, some people collect them for their budgies to peck at.
What do cuttlefish look like?
Like other cephalopods (which is Greek for ‘head foot’), a cuttlefish’s arms and tentacles are attached to its head. They come in a huge variety of sizes. Flamboyant cuttlefish are the smallest species, no bigger than 8cm long. True to their name, giant cuttlefish are the largest and can grow to a metre in total length.
They are known for their incredible skin which can change colour and texture to camouflage into their surroundings when they need to hide from predators. They can also use this startling colour-changing ability to communicate with other cuttlefish, sending messages by broadcasting different patterns across their skin. These intelligent animals can also use these signals to play tricks. Researchers have seen male cuttlefish putting on female displays to trick rival males into letting them get close to a female.
What do cuttlefish eat?
Cuttlefish tend to eat shrimp, crabs, fish and even other cuttlefish. There is no parental care in cuttlefish and babies are fully independent as soon as they hatch. Researchers believe they are already learning what foods are good to eat by watching the outside world from inside their egg.
Scientists have shown that these intelligent animals can remember what they ate and how long ago, and that they have self-control. When put through the ‘marshmallow test’ – which tests whether species will delay gratification for a better treat – the cuttlefish passed, unlike many human toddlers.
How do cuttlefish protect themselves?
Unlike many other marine molluscs, cuttlefish don’t have a hard external shell to protect themselves from predators. They are preyed upon by many other animals, including sharks and dolphins. So, cuttlefish spend most of their lives hiding from danger but the crafty creatures also use their wits to keep themselves safe.
These talented illusionists have around 10 million colour-changing cells in their skin called chromatophores that allow them to adapt their hue to blend into the background. They can also turn these cells on and off separately, enabling them to blast distracting patterns across their skin when they need to confuse a wannabe predator. They also use their camouflage when hunting: broadclub cuttlefish (Sepia latimanus) have been seen impersonating a leaf and branching coral as they try to sneak up on a tasty snack.
As an extra party trick, some species squirt a mixture of ink and mucus when under attack. This distracting decoy gives them a chance to make a quick escape.
Can cuttlefish hypnotise humans?
No, cuttlefish can't hypnotise humans – nor its prey. But the cuttlefish does employ its incredible colour-changing abilities to trigger a freeze response so that it can strike.
How do cuttlefish swim?
Inside a cuttlefish’s body is a porous structure called the cuttlebone. This is how cuttlefish control their buoyancy. A little bit like a scuba diver’s buoyancy control device (BCD), they can adjust the levels of gas within the cuttlebone depending on whether they want to float up or sink down.
The fin that circles around the cuttlefish’s entire body helps it to swim along and they can also move using jet propulsion. When they want to put on a burst of speed, they fill their bodies with water before shooting it out to thrust forward.
Are cuttlefish under threat?
Generally, cuttlefish aren’t considered under threat. Common cuttlefish are abundant in UK waters and are categorised as a species of least concern by the IUCN Red List of Threatened Species.
Cuttlefish are heavily fished in UK waters. In 2018, cuttlefish was the fifth most valuable fishery in England even though we don’t really eat it here. Most of the catch from UK waters is exported to Europe: in particular, Italy, France, and Spain.
Special features of a cuttlefish:
- Mantle
- Eyes with W-shaped pupils
- Colour-changing skin
- Cuttlebone
- Skirt-like fins around mantle
- Beak
- Eight arms
- Two tentacles
Cuttlefish at a glance
- Scientific family name: Sepiidae
- Nicknames: Chameleons of the sea
- Length: Between 2.5cm and 1m depending on the species
- Average lifespan: One or two years
- Weight: Up to 10.5 kg
- Depth: Usually live in shallow waters but have been found as deep as 600m
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