Fun cuttlefish facts

November 15, 2023

As a marine science writer, I love to learn about the cool creatures that live in our seas. But, often, the same species – such as whales, octopus and sharks – get all the love. So, today I wanted to dive into an animal that doesn’t always get the attention it deserves. Are you ready for some fun facts about… cuttlefish?

First of all, cuttlefish are not, in fact, fish – they’re a type of cephalopod related to octopus and squid. You may already know that they can change colour but did you know they’re colourblind? The fact that they squirt ink is fairly common knowledge. But did you know they can make that ink squirt look like a body double?

Fun facts

  • Like the octopus, cuttlefish have three hearts and blue blood. Inside the cuttlefish’s main body – which is called the mantle – is a porous structure called the cuttlebone. The animal uses this like a scuba diver’s BCD (buoyancy jacket): adjusting the levels of liquid or gas within it to sink or float up.
  • They use jet propulsion when they want to move fast: filling their body cavities with water, then squirting it out to propel themselves backwards.
  • Cuttlefish have among the largest brain-to-body size ratio of all invertebrates. These super-intelligent animals can count, can remember what, where and when they last ate (which we once thought only humans could do) and can even exhibit self-control: choosing to pass on a treat if they know they’ll be rewarded for waiting with their favourite snack.
  • Their skin has 10 million colour cells, which can change not only colour but pattern and texture. Despite this, they are colourblind!
  • But they make up for it by being able to see almost entirely behind them. This is due to their w-shaped pupils, which also allow them to look forwards or sideways.
  • Cuttlefish start learning while they are still larvae. Since the parents leave them to fend for themselves as soon as they are born, they are taught to find food while they are still in their egg casing.
  • The same astonishing camouflage skills they employ to avoid being eaten also come in handy when they attack prey. They change colour to blend into their surroundings, pretend to be other species and make shapes with their tentacles to complete the illusion. Sometimes they freeze, even slowing their breathing to avoid detection.
  • Jet propulsion comes in handy, too! Plus, that distracting cloud of ink is sometimes mixed with mucus to create a ‘pseudomorph.’ Taking the shape of their body, they use this as a decoy.
  • But possibly the best fact of all is that researchers used live shrimp (yum!) to entice cuttlefish to wear 3D glasses. But why? They were trying to learn more about how the species' vision works.

Scary facts

  • To keep the female interested, the male cuttlefish can make one side of his body look appealing to her while the other side looks like a female to deter any rivals hanging around.
  • They may look squishy but a male cuttlefish will fight off any rivals, grabbing, biting and twisting each other until one is victorious – and gets the girl!

How you can help

  • Support your local Wildlife Trust and find out what they are doing to protect the cuttlefish.
  • Increasing levels of CO2 affect the acidity of the oceans, which in turn  represents a threat to cuttlefish. We all need to be doing what we can to drastically reduced CO2 emissions both in our personal lives and by supporting global efforts to make positive changes.

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