Sometimes when you walk on the beach you might see more animals, or should I say parts of animals, then you think. One of these animals are cuttlefish. You might have seen these white oval pieces of bone. This is a cuttlebone from the cuttlefish, although it’s not really a bone but the internal calcified shell of a cuttlefish. The cuttlebone is used to control the buoyancy of the animal, it can take hours for the cuttlefish to change its buoyancy. However the cuttlefish can still change its position with the fins that surround its body. Cuttlefishes are molluscs and closely related to octopuses and squids and together they form the family of Cephalopods. And these Cephalopods have some special abilities.
Special abilities
Cuttlefish are truly interesting animals with special abilities. For one they can change the colour of their body. The cuttlefish is covered with millions of pigment cells (chromatophores) on its skin. They use these pigment cells to change colour in order to camouflage (hide), however it is also used to hunt, attract mates and to communicate. It is not just the colour of their skin that they can change, they can also change the texture of their skin. They can do this by extending or retracting tiny bumps called papillae which are located across their bodies. By doing this they can better match their surroundings in order to hide. So they can change the colour of their skin, but it gets strange as they actually are colour-blind. Even though they are colour-blind their eyes are very developed and can see very well in low light. They have a great perception of contrast as they can detect polarized light. The eyes of the cuttlefish are very large in proportion to its body, the W- shaped pupil controls the intensity of the light entering the eye. The changing of colours and texture of their skin can be done in a matter of seconds.
In the front of its buddy the cuttle fish has 6 arms which are used to hold the prey and 2 tentacles which are used to catch their prey. Their prey include crabs, shrimps, fishes and other cephalopods. When they caught the prey with their tentacles, they hold the prey with their arms while they eat. Cuttlefish’s mouth is quite similar to a parrots beak. Both the arms and tentacles are covered in suckers. When in danger the cuttlefish can also use its arms in order to appear larger. Another defensive mechanism is their ability to produce a brown ink called sepia, which is dispersed as a cloud behind which the cuttlefish can escape.
Cuttlefish have three hearts. Two hearts are used to pump blood to the gills and the third heart circulates the oxygenated blood to the rest of its body. Next to having large eyes compared to their body they also have a large brain compared to their body. With their brain they can handle senses such as smell, sight and even sound. They can’t hear anything but they can fell pressure waves from sounds in the water. The brain also plays the biggest part in the changing of colour and texture of their bodies.
Cuttlefishes can be found everywhere in the worlds (coastal) seas. In the winter they move to deeper waters, and in spring/summer they return to coastal waters for mating and laying the eggs. The life span of cuttlefish is very short with an average of 1 to 2 years. As females lay 100 to 300 eggs and after which they die. Even though they live short they do grow rather quickly and can reach the size of 50/75cm and can weigh up to 5kg.
There are 100 different species of cuttlefish in the world. In the North-Sea we can mostly find the common cuttlefish (Sepia officinalis).
Aren’t they something special, I always love seeing cuttlebones on the beach as it is a sign that they are still present in the sea.
Sources
Elucidating Cuttlefish Camouflage. Max Planck Institute for Brain Research. https://www.mpg.de/12363924/1017-hirn-080434-elucidating-cuttlefish-camouflage
Okamoto, Kohei, et al. "Unique Arm-Flapping Behavior of the Pharaoh Cuttlefish, Sepia pharaonis: Putative Mimicry of a Hermit Crab." Journal of Ethology, vol. 35, 2017, 307-311, doi:10.1007/s10164-017-0519-7 . https://link.springer.com/article/10.1007/s10164-017-0519-7
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