Truly Incredible Facts about Cuttlefish

Facts about Cuttlefish
The cuttlefish is not a fish. In fact, it is a mollusk, and is well-known for its chameleon-like behavior. Certain facts about the cuttlefish are enlisted in the AnimalSake article below.
AnimalSake Staff
Last Updated: Jan 11, 2018
Quick Fact:
The cuttlefish belongs to the Sepiida class, which also includes the Squids, the Octopus, and the Nautiluses.
As mentioned in the description, the cuttlefish is not a fish, but it is most certainly a marine creature. It is an invertebrate, and one of the most intelligent ones at that, as depicted by recent research studies. It has an average life span of around 2 years. It gets its name from an old English usage of 'cudele'. Studied by scientists and researchers, this mollusk is one very interesting creature. The following paragraphs present to you all that you need to know about the cuttlefish.
Classification
Kingdom          :   Animalia
Phylum             :   Mollusca
            Class               :   Cephalopoda
Order               :   Sepiida
                Superorder      :   Decapodiformes
Anatomy
Cuttlebone
cuttlefish bone
  • The bone of the cuttlefish is known as the cuttlebone.
  • It is made of aragonite and is unique to the cuttlefish.
  • The shape, size, and pattern (ridges/texture) vary in each of the species of cuttlefish.
  • It is used as a calcium supplement for birds, turtles, chinchillas, reptiles, and hermit crabs.
  • It is also used as a mold in jewelry making.
Body
Close Up Of Cuttlefish
  • They do not have a tail; instead, they have a fin all the way round their body, which they use for movement.
  • Cuttlefish use jet propulsion to escape from enemies. This feat is accomplished when water is squeezed down their mantle (body) into a siphon (tubular muscle that controls direction), and they are propelled backwards.
  • On an average, the size of a cuttlefish ranges from 15 to 25 cm, i.e., 5.9 to 9.8 inches. The largest species - Sepia apama, reaches to about 50 cm, i.e., 20 inches in mantle length. The smallest are the Stumpy-spined cuttlefish, the Sepia bandensis, and are 7 cm. They are found in the Alas Strait in Indonesia.
  • These cephalopodas have eight arms. Additionally, they have two tentacles that have denticulated suckers, which help them secure their prey.
Skin and Camouflage
cuttlefish camouflage
  • They are known as the 'chameleons of the sea', because their skin can change color rapidly.
  • The color and texture change is a defense mechanism towards potential predators.
  • The color-changing ability of the cuttlefish occurs due to pigmented chromatophores (red, yellow, brown, and black), which have a large membrane and sac of pigment that folds when retracted.
  • Color Cells
    • Yellow chromatophores (xanthophores) - closest to the surface of the skin
    • Red and orange - below (erythrophores)
    • Brown or black - just above the iridophore layer (melanophores)
    • iridophores (plates of chitin or protein) - reflect blue and green light
  • The above mentioned cells can be used in combination in every way possible.
  • Cuttlefish can also sense and react to the light's polarization, which it uses to send signals to other sea creatures that can sense polarization.
  • This cephalopoda, assesses its surroundings and accordingly changes its color.
  • It can also camouflage itself in pitch black oceans and also in complete darkness.
Eyes
cuttlefish eye
  • The cuttlefish does not have any blind spot as the position of the optic nerve is behind the retina.
  • Even though cuttlefish are colorblind, they have sophisticated eyes. It is believed that this cephalopoda starts observing its surroundings when it is in the egg itself.
  • The pupil of the cuttlefish's eye is the shape of a 'W'.
  • Although colorblind, cuttlefish can perceive light polarization and react to it.
  • This cephalopoda changes position of the entire lens to change focus as compared to mammals, who reshape the lens.
Circulation
  • Their blood is bluish green, as the protein hemocyanin contains copper instead of iron, or hemoglobin, which is found in the blood of vertebrates.
  • The cuttlefish has three separate hearts: one for the body, and two branchial hearts to pumps blood to each gill.
  • The flow is blood in the body of this mollusk is more rapid as compared to other animals, because hemocyanin carries less oxygen.
Ink and Toxicity
cuttlefish ink
  • The original sepia ink used by artists was extracted from the cuttlefish, though nowadays, it is replaced by a synthetic ink.
  • The ink is shot out of the fish as a defense mechanism to confuse predators and to make a quick escape.
  • All cuttlefish have neurotoxins in their saliva that are produced by bacteria, but not all cuttlefish are poisonous.
  • The toxins found on the Metasepia pfefferi, which is also known as the flamboyant cuttlefish are seen to be as lethal as the toxins found in the blue-ringed octopus.
  • The only known species of the cuttlefish that is known to have poisonous flesh is the flamboyant cuttlefish.
flamboyant cuttlefish
Flamboyant Cuttlefish
Ecology
Diet and Habitat
crab on rock
  • This mollusk likes to feed on small shrimp that have just hatched, crabs, and other fish.
  • They use their camouflaging abilities to hunt down their prey.
  • They shoot jets of water to uncover their prey from the sand and grab them with their tentacles when they are trying to escape.
  • Their prey is then paralyzed by their poison and eventually eaten.
  • Cuttlefish prefer shallow tropical waters.
  • They are mostly found in the Mediterranean Sea, Baltic Sea, shallow waters of South Africa, Australia, Malaysia, the Philippines, and the English Channel.
Mating
cuttlefish mating
  • During the mating season, male cuttlefish challenge each other for dominance.
  • Direct contact is usually not made between two males during their 'battle' for dominance, they just threaten each other till one of them backs down and swims away.
  • Sometimes though, when a large cuttlefish is threatened by another male, then the cuttlefish does attack and tries to make the other one flee.
  • Cuttlefish can get very aggressive, as there are roughly four or five cuttlefish ambling for the same female.
  • These fish grow very fast, hence the possibility of them finding a mate when they are bigger is always high as compared to them finding a mate when they are smaller in size.
  • Another interesting trait displayed by this animal during its mating ritual is: if the cuttlefish is a smaller one, it disguises itself as a female by changing its colors and hiding its extra arms or even pretending to hold an egg sac.
  • Due to their size and disguise, they can easily swim past a male guarding the female and mate with her.
  • The male fish inserts sperm sacs into an opening near the females mouth by using a specialized tentacle.
  • A few hours later, once the eggs are laid, the male guards the female and the eggs.
Apart from sharks, monkfish and swordfish, the cuttlefish has another huge predator - the human. Cuttlefish are used in food preparations, aquariums, and also bred for their ink and cuttlebone.
Cuttlefish are caught all over the world for delicacies like risotto in black sauce (the black sauce is the ink), fried snacks, deep-fried cuttlefish, fish stews etc.
Research activities like studying the camouflaging mechanism and trying to replicate that is another reason why this cephalopoda is caught. Now that you know more about this unusual creature, you can help in its conservation even though it is not an endangered species.