Cuttlefish

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 are among the most intelligent invertebrate species.

Cuttlefish have an internal shell (cuttlebone), large W-shaped pupils, 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. Their life expectancy is about one to two years.

Overview

The mollusks (American spelling) or molluscs (British spelling) are the large and diverse phylum (Mollusca) of invertebrates that includes a variety of familiar animals well-known for their decorative shells or as seafood. These range from tiny snails, clams, and abalone to the octopus, cuttlefish, and squid (which have complex nervous systems and are considered the most intelligent invertebrates).

Mollusks are characterized by having a true coelom; a body typically divided into the three parts of head, visceral mass, and muscular foot; organ systems for circulation, respiration, digestion, excretion, nerve conduction, and reproduction; and most mollusks have one or more shells and are bilaterally symmetrical (Towle 1989). Unlike the closely related annelids, mollusks lack body segmentation.

Mollusks are generally organized into nine or ten classes, with one that is known only from fossils, but the others with extant (living) representatives.

• Class Cephalopoda — squid, octopus, nautilus, cuttlefish; 786 species, all marine; have a large well-developed head and prominent foot with many tentacles (cephalopod means "head-foot").

Cephalopods (Greek plural Κεφαλόποδα (kephalópoda); "head-foot") are marine mollusks (phylum Mollusca) of the class Cephalopoda, a group that includes the familiar octopus and squid. Cephalopods are characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot into the form of arms or tentacles surrounding the mouth, which has beak-like jaws. Cephalopods have the most complex nervous system among invertebrates, and large and image-focusing, vertebrate-like eyes. The highly developed neural organs allows them to have an excellent capacity to learn and remember; nonetheless, most are short-lived, in the order of months or a few years.

The class Cephalopoda contains two extant (living) subclasses. In the Coleoidea, the mollusk shell has been internalized or is absent; this subclass includes the octopuses, squids, and cuttlefish. In the Nautiloidea, the shell remains; this subclass includes the nautilus.

Squids belong to the subclass Coleoidea along with octopuses, cuttlefish, and extinct belemites. They differ from octopuses in that octopuses have eight arms and no tentacles, while squids and cuttlefish, at some point in their life cycle, have eight arms and two tentacles. (Tentacles tend to be longer than arms and usually have suckers as their tips only.) The suckers of squids also have hooks and/or sucker rings, while octopuses have simple suckers without secondary armature (O'Shea 2006). Squids differ from the squid-like cuttlefish in that cuttlefish have an internal shell (cuttlebone) on their back. Some squid species lose their tentacles in post-larval stages, and thus the adult only has eight arms (O'Shea 2006).

Squids are marine cephalopods (class Cephalopoda, phylum Mollusca) with ten arms and tentacles (at some point in life), secondary armature on their suckers, and lacking the internal shell specific to cuttlefish. (Cuttlefish possess an internal structure called the cuttlebone)

With the exception of Nautilus, cephalopods have special skin cells called chromatophores that change color and are used for communication and camouflage. Cuttlefish are known as "chameleons of the sea" for their ability to change skin color and patterns. (See camouflage.) A cuttlefish can not only rapidly change its colors, color patterns, and color intensity to blend with its background, but this cephalopod can even change skin texture to match its habitat, better concealing itself as its moves among the various sandy areas, corals, and rocks of its marine environment. Cuttlefish are known as "chameleons of the sea" for their ability to change skin color and patterns, although the cuttlefish color changes are actually much faster and more intricate than that of the chameleon, changing as they swim over different surfaces.

Octopuses and cuttlefish are also noted for the ability to change the texture of their skin to match their environment, such as having bumpy projections when over a coral reef or smooth skin when over sand.

Anatomy

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 cuttlebone. The cuttlebone is unique to cuttlefish, one of the features contrasting them with their squid relatives. 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 caged birds and snails as a source of dietary calcium.

Changing color

An infant cuttlefish protects itself with camouflage

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

A close up of a cuttlefish eye.

Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes differs fundamentally from that of vertebrates like humans. Superficial similarities between cephalopod and vertebrate eyes are thought to be 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 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 pulled around by reshaping the entire eye in order to change focus.

Scientists have speculated that cuttlefish's eyes are fully developed before birth and start observing their surroundings while still in the egg. One team of French researchers has additionally suggested that cuttlefish prefer to hunt the prey they saw before hatching.

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

File:Metasepia pfefferi 1.jpg

Pfeffer's Flamboyant Cuttlefish from Sipadan, Malaysia

Recently it has been discovered that the Pfeffer's Flamboyant Cuttlefish's muscles contain a highly toxic compound that is yet to be identified. 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.

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]}

Classification

Wikispecies has information related to:

Sepiida

Sepia officinalis from Turkish waters

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

As food

Linguine with cuttlefish and ink sauce served at a Venetian osteria

commercial
mollusks
abalone
clams
cockles
periwinkles
mussels
oysters
scallops
cephalopods
fisheries
I N D E X

Cuttlefish are caught for food in the Mediterranean, East Asia, the English Channel and elsewhere. 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 al Nero di Seppia (literally black cuttlefish rice). 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

Eugenio Montale's ground-breaking debut collection of poetry Cuttlefish Bones (Ossi di seppia) was 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.

A 1923 drama by Stanisław Ignacy Witkiewicz is titled The Cuttlefish.

In his story The Call of Cthulhu, author H.P. Lovecraft likens the evil alien god's head to that of a cuttlefish.

In Rudy Rucker's 2007 novel Postsingular cuttlefish have mythical significance to people in a parallel universe (where they have already been fished to extinction). These "hibrane people" travel to our world to catch them, or steal them from fisherman's catches, causing them to mysteriously disappear.

In South Sea Adventure, by Willard Price, the protagonists are warned of a "fifty-foot cuttlefish". As no such cuttlefish exists, it is probable the creature described was a squid.

In the Poetry Collection 'Dragons' by Matthew Francis, there is a poem titled 'What the Cuttlefish Do', which makes various references to Cuttlefish, including their ability to change colour and mating habits.

References

ISBN links support NWE through referral fees

• O'Shea, S. 2006. Giant Squid and Colossal Squid Fact Sheet. Tonmo (The Octopus News Magazine Online). Retrieved January 21, 2007.

http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=82331 Sepiida Zittel, 1895 Taxonomic Serial No.: 82331 1999

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 a tiny cuttlefish.
• YouTube video of cuttlefish hovering about. You can see colour changes and movement.
• YouTube video with excellent examples of color and texture modulation.
• Youtube video Cuttlefish changing colour and shape
• Amazing cuttlefish - Cephalopods with natural camouflage and sepia ink
• Diving with cuttlefish
• PBS.org - Nova - Kings of Camouflage

Credits

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