Cuttlefish
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 Two cuttlefish interact while a third looks on. Georgia Aquarium
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Cuttlefish are sea animals of the order Sepiida belonging to the Cephalopoda class (which also includes squid, octopuses and nautiluses). Despite their common name, cuttlefish are not fish, but molluscs.
Cuttlefish have an internal shell (called cuttlebone), large eyes, and eight arms and two tentacles furnished with denticulated, or finely toothed, suckers, with which they secure their prey.
Cuttlefish eat small molluscs, crabs, shrimp, fish and other cuttlefish, but can be eaten by predators, including sharks, fish, and other cuttlefish. They live about 1 to 2 years.
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[change] Anatomy
[change] Cuttlebone
Cuttlefish have an internal structure called the cuttlebone. This is composed of calcium carbonate. It is porous, or full of small holes, in order to allow the cuttlefish the swim, not sink. Its buoyancy can change (for example, allowing the cuttlefish to go lower or higher) by changing the amount of gas and liquid in the chambers of the cuttlebone. Each species has a distinct shape, size, and pattern of ridges or texture on the cuttlebone. Cuttlebones are traditionally used by jewelers and silversmiths as molds for casting small objects. They are probably better known today as the tough material given to parakeets and other pet birds as a source of calcium for their diets. The cuttlebone is only found in cuttlefish, and is one of the features that makes them different from squid and other molluscs.
[change] Changing color
Cuttlefish are sometimes called the chameleon of the sea because they are able to change their skin color whenever they want. Their skin can flash a colorful pattern in order to communicate with other cuttlefish and to camouflage them from predators. This color-changing function is produced by groups of red, yellow, brown, and black pigmented chromatophores above a layer of reflective iridophores and leucophores, all of these being parts of the cuttlefish's skin which help it change its color. There are up to 200 of these special pigment cells per square millimeter. The pigmented chromatophores have a sac of pigment and a large membrane that is folded when retracted. There are 6-20 small muscle cells on the sides which can contract to squash the elastic sac into a disc against the skin. Yellow chromatophores (xanthophores) are closest to the surface of the skin, red and orange are below (erythrophores), and brown or black are just above the iridophore layer (melanophores). The iridophores reflect blue and green light, which make them look blue and green. Iridophores are plates of chitin or protein, which can reflect the area around a cuttlefish. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. All of these cells can be used in combinations. For example: orange would be produced by red and yellow chromatophores, while purple could be created by a red chromatophore and an iridophore. The cuttlefish could also use an iridophore and a yellow chromatophore to produce a brighter green. As well as being able to influence the color of the light that reflects off their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other sea animals, many of whom can also sense polarization.
[change] Eyes
Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes is fundamentally different from that of vertebrates like humans.[1] Superficial, or insignificant, similarities between cephalopod and vertebrate eyes are examples of convergent evolution. The cuttlefish pupil is a smoothly-curving W shape. Although they cannot see color, they can perceive the polarization of light, which essentially enhances their ability to see contrast. They have two spots of concentrated sensor cells on their retina (known as fovea), one to look more forward, and one to look more backwards. The lenses, instead of being reshaped as they are in humans, are instead pulled around by reshaping the entire eye in order to change focus.
[change] Blood
The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein hemocyanin to carry oxygen instead of the red iron-containing protein hemoglobin that is found in mammals. The blood is pumped by three separate hearts. Two of these are used for pumping blood to the cuttlefish's pair of gills (one heart for each gill), and the third for pumping blood around the rest of the body. A cuttlefish's heart must pump a more blood than most other animals because hemocyanin is not as good at carrying oxygen as hemoglobin is.
[change] Ink
Cuttlefish have mouths like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia. However, there is an increased amount of Jews in modern times using the ink for the techelet dye on their Tallit strings.
[change] Cuttlefish as food
Cuttlefish are caught for food in Mediterranean, and East Asian cultures. Although squid is more popular as a restaurant dish all over the world, in East Asia dried cuttlefish is a highly popular snack food.
Cuttlefish is especially popular in Italy, where it is used in Risotto Nero, and in the Croatian Crni Rižot, which is almost the same and originated most probably from Venice, then spread across both coasts of the Adriatic. "Nero" and "Crni" mean black, which is the color the rice turns because of the cuttlefish ink. Spanish cuisine, especially that of the coastal regions, often uses cuttlefish and squid ink for cooking due to the marine flavor and smoothness that it provides to the meals and it is included in dishes such as rice, pasta and fish stews.
[change] Cuttlefish in literature
Cuttlefish made their most important literary appearance in the title of Eugenio Montale's ground-breaking debut collection of poetry entitled Cuttlefish Bones (Ossi di seppia), published in Turin in 1925. Montale, who grew up in Liguria along the Mediterranean Sea, was awarded the Nobel Prize for Literature in 1975, for his long and prolific career. Cuttlefish Bones remains one of the best-known and influential collections of 20th-century poetry.
In the science-fiction novel Frek and the Elixir, by Rudy Rucker, an alien named Professor Bumby shows himself to the main character, Frek, in the form of a cuttlefish.
[change] Classification
There are over 120 species of cuttlefish currently recognized, grouped into 5 genera. Sepiadariidae contains seven species and two genera; all the rest are in Sepiidae.
- CLASS CEPHALOPODA
- Subclass Nautiloidea: nautilus
- Subclass Coleoidea: squid, octopus, cuttlefish
- Superorder Octopodiformes
- Superorder Decapodiformes
- Order †Boletzkyida
- Order Spirulida: Ram's Horn Squid
- Order Sepiida: cuttlefish
- Suborder †Vasseuriina
- Family †Vasseuriidae
- Family †Belosepiellidae
- Suborder Sepiina
- Family †Belosaepiidae
- Family Sepiadariidae
- Family Sepiidae
- Suborder †Vasseuriina
- Order Sepiolida: bobtail squid
- Order Teuthida: squid
[change] Other websites
- Scientific Database with photos and videos of cuttlefish and other cephalopods
- TONMO.com offers articles and forum discussion on cuttlefish care
- YouTube video of a cuttlefish harassing a diver
- YouTube video of cuttlefish hovering about. You can see colour changes and movement.
- Amazing cuttlefish - Cephalopods with natural camouflage and sepia ink
- Diving with cuttlefish
