cuttlefish

 

common name applied to cephalopod mollusks that have 10 tentacles, or arms, 8 of which have muscular suction cups on their inner surface and 2 that are longer and can shoot out for grasping prey, and a reduced internal shell enbedded in the enveloping mantle. The body is short, broad, and flattened. Cuttlefish are carnivorous and excellent at capturing prey with their arms. Although good swimmers, they are not as fast as the related squids, but like the squids cuttlefish have lateral fins used as stabilizers and for steering and propulsion. They swim by jet propulsion, forcibly expelling water through a siphon. During the day they lie buried in the bottom of the ocean; at night they swim and hunt for food. Except for the squid genus Loligo, cuttlefish have the best cephalopod eyes, which are highly complex. When disturbed, cuttlefish eject a cloud of dark brown ink from an ink sac for protection. The ink gland and ink sac are specializations of the rectal gland. The ink is composed mostly of melanin and has been used as the artist's pigment, sepia. All cuttlefish are dioecious, i.e., the sexes are separate. The common, worldwide, deepwater cuttlefish, genus Spirula, is considered a “living fossil” because it possesses a remnant of the external shell of the ancient cephalopods. These cuttlefish have a small, coiled internal shell containing a bubble of gas (nitrogen), which serves as a float in the ocean. The European cuttlefish, Sepia officinalis, possesses a degenerate internal shell composed of lime, which is popularly called cuttlebone. Within the narrow spaces between the thin septa of the shell are fluid and gas (mostly nitrogen), which give the organism buoyancy. These cuttlefish are found in the Mediterranean and E Atlantic. The cuttlebone is used for pet birds as a source of lime salts. Sepia are able to undergo a complex of color changes ranging from pink to brown with varying stripes and spots, usually displayed when they are disturbed. The eggs, deposited singly and attached by a stalk to objects on the ocean bottom, are extremely large, up to .6 in. (15 mm) in diameter. The smallest cuttlefish, Idiosepius, inhabits tide pools and attains a length of .6 in. (15 mm). Cuttlefish are classified in the phylum Mollusca, class Cephalopoda, order Sepioidea.

Cuttlefish
Two cuttlefish interact while a third looks on. Georgia Aquarium
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Subclass: Coleoidea Superorder: Decapodiformes Order: Sepiida Zittel, 1895
Suborders and Families
†Vasseuriina †Vasseuriidae †Belosepiellidae Sepiina †Belosaepiidae Sepiadariidae Sepiidae

Cuttlefish are marine 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. Recent studies indicate that cuttlefish may be the most intelligent invertebrate species. ^[1]

Cuttlefish have an internal shell (cuttlebone), large W shaped eyes, and eight arms and two tentacles furnished with denticulated suckers, with which they secure their prey.

Cuttlefish eat small molluscs, crabs, shrimp, fish and other cuttlefish. Their predators include dolphins, sharks, fish, seals and other cuttlefish. They live about 1 to 2 years.

Anatomy

Cuttlebone

Main article: Cuttlebone

Cuttlefish possess an internal structure called the cuttlebone, which is porous and composed of calcium carbonate, to provide the cuttlefish with buoyancy. Buoyancy can be regulated by changing the gas-to-liquid ratio in the chambered cuttlebone. Each species has a distinct shape, size, and pattern of ridges or texture on the "bone". Cuttlebones are traditionally used by jewelers and silversmiths as moulds for casting small objects. They are probably better known today as the tough material given to parakeets and other cage birds as a source of dietary calcium. The cuttlebone is unique to cuttlefish, one of the features contrasting them with their squid relatives.

Changing color

Cuttlefish are sometimes called the chameleon of the sea because of their remarkable ability to rapidly alter their skin color at will. Their skin flashes a fast-changing pattern as communication to 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, with up to 200 of these specialized 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. Iridophores are plates of chitin or protein, which can reflect the environment 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 is produced by red and yellow chromatophores, while purple can be created by a red chromatophore and an iridophore. The cuttlefish can 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 marine animals, many of which can also sense polarization.

Eyes

Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes differs fundamentally from that of vertebrates like humans.^[2] Superficial 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,^[3] they can perceive the polarization of light, which enhances their perception of 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.

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 which 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 higher blood flow than most other animals because hemocyanin is substantially less capable of carrying oxygen than hemoglobin.

Toxicity

Recently it has been discovered that the Pfeffer's Flamboyant Cuttlefish's muscles contain a highly toxic compound that is yet to be identified. ^[1] Research by Mark Norman with the Museum Victoria in Queensland, Australia has shown the toxin to be as lethal as that of a fellow cephalopod, the Blue-ringed octopus.^[4]

Ink

Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia. However, there is a modern resurgence of Jewish people using the ink for the techelet dye on their Tallit strings.^{[citation needed]}

As food

Cuttlefish are caught for food in the Mediterranean and East Asia. Although squid is more popular as a restaurant dish all over the world, in East Asia dried shredded cuttlefish is a highly popular snack food.

Cuttlefish is especially popular in Italy, where it is used in Risotto Nero. The Croatian Crni Rižot is virtually the same recipe, which probably originated in Venice and then spread across both coasts of the Adriatic. "Nero" and "Crni" mean black, the color the rice turns because of the cuttlefish ink. Spanish cuisine, especially that of the coastal regions, uses cuttlefish and squid ink for the marine flavor and smoothness it provides; it is included in dishes such as rice, pasta and fish stews.

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 popular novel Twenty Thousand Leagues Under the Sea by Jules Verne, Captain Nemo and his companions engage in a fierce battle with a group of giant cuttlefish. Although the creatures are defeated, one of the crew members is killed during the fight. Although Jules Verne accurately describes the cuttlefish's three hearts, he describes their blood as being red, instead of its actual greenish tint.

Classification

There are over 120 species of cuttlefish currently recognised, grouped into 5 genera. Sepiadariidae contains seven species and 2 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
      • Order Sepiolida: bobtail squid
      • Order Teuthida: squid

References

External links

• 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.
• YouTube video with excellent examples of color and texture modulation.
• Amazing cuttlefish - Cephalopods with natural camouflage and sepia ink
• Diving with cuttlefish
• PBS.org - Nova - Kings of Camouflage
• Google Video - Nova - Kings of Camouflagezh-yue:墨魚

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