Discover these fascinating facts about the colour-swapping cephalopod.
- Weirdest fish: The strangest fish in the world, including one that can incredibly live out of water for more than two months
- Deadliest fish on the planet: you won't want to meet these fearsome species underwater
Cuttlefish facts
- Cuttlefish can grow to nearly a metre long, reaching a weight of up to 16kg.
- Cuttlefish have some of the most impressive courtship routines in nature. Big males adopt a striking zebra-stripe pattern on one side of their body to ward off rivals, while simultaneously displaying an attractive mottled pattern to a female on the other – quite a feat. But what if you’re not a large male able to scare off competitors? Some little ’uns ingeniously turn a dappled colour, round out their body shape and act very demure, exactly like a female.
- Cuttlefish can change colour in 200 milliseconds, as fast as a human can blink.
- Cuttlefish have W-shaped pupils, which are thought to help control the intensity of light entering the eye.
- Cuttlefish have three hearts, two of which pump blood to its gills, while the third circulates blood around the body.
- Cuttlefish have blue blood (like horseshoe crabs), so-coloured thanks to the copper-rich protein it contains known as hemocyanin, which transports oxygen around the body. (Mammal blood is red due to its iron-rich haemaglobin, which does the equivalent job.)
- Cuttlefish have eight arms, which are designed to grasp prey and for use in self-defence, plus two feeding tentacles.
- Cuttlefish have a doughnut-shaped brain, boasting the largest brain-to-body ratio of all invertebrates.
- Cuttlefish can squirt clouds of ink, using brown ink stored in an ink sac, to create a smokescreen and escape predators.
- Cuttlefish might dream. Researchers filming European cuttlefish in the lab observed short periods during their sleep-like states where individuals would erratically change colour and body pattern, and make irregular eye and arm movements. This strange behaviour, which was not repeated when awake or during inactive periods of ‘sleep’, wasn’t triggered by any external stimuli and was very different from normal cuttlefish activity. Do cuttlefish dream? No one knows, but we have our first clue.
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