Cuttlefish
From Free net encyclopedia
{{Taxobox
| color = pink
| name = Cuttlefish
| image = Georgia Aquarium - Cuttlefish Jan 2006.jpg
| image_width = 250px
| image_caption = Two cuttlefish interacting at the Georgia Aquarium
| regnum = Animalia
| phylum = Mollusca
| classis = Cephalopoda
| subclassis = Coleoidea
| superordo = Decapodiformes
| ordo = Sepiida
| ordo_authority = Zittel, 1895
| subdivision_ranks = Families
| subdivision =
Sepiadariidae
Sepiidae
}}
Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus.
Cuttlefish have an internal shell, large eyes, and eight arms and two tentacles furnished with denticulated suckers, by means of which it secures its prey.
Cuttlefish possess an internal structure called the cuttlebone, which is composed of calcium carbonate and is porous to provide the cuttlefish with buoyancy. Buoyancy can be regulated — the cuttlefish can even decide to sink — 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 jewellers 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 bill-sharpener and source of dietary calcium.
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 chromatophores above a layer of iridophores, and then a layer of leucophores, with up to 200 of these specialized pigment cells per square millimeter. The chromatophores are a cell with a bag of ink 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 ink sac into a disc against the skin. Yellow chromatophores are closest to the surface of the skin, red and orange are below, and brown or black are just above the iridophore layer. 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 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 colour of the light that reflects off their skin, cuttlefish can also effect the light's polarisation, which can be used to signal to other marine animals, many of whom can also sense polarisation.
Cuttlefish eyes are among the most developed in the animal kingdom. They have similar eyes to humans, but the pupil is a smoothly-curving "w" shape. Although they cannot see color, they can perceive the polarity of light, which essentially 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.
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.
Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia. Cuttlefish are caught for food, though squid is more popular.
Cuttlefish eat small molluscs, crabs, shrimp, fish and other cuttlefish. Their predators are sharks, fish, and other cuttlefish. They live about 1 to 2 years.
Like octopuses, cuttlefish have been successfully raised as pets in home aquariums, even though they demand intensive attention to maintenance. In particular, cuttlefish need a minimum amount of sea water in proportion to their body size, their tank needs to be cleaned every time they ink, they cannot tolerate abrupt changes in light levels, and they cannot coexist with other animals, and rarely ever with other cuttlefish. All other animals of comparable or smaller size, including other cuttlefish, are instinctively seen as food.
Domestic cuttlefish are oddly reminiscent of domestic cats, even exhibiting cat-like habits such as resting, pouncing on moving prey or balls of yarn, begging owners for food, and even begging for more food than they need or is healthy for them. Like cats, cuttlefish are not truly tame, but rather tolerate and cooperate with their owners to live a comfortable life. But unlike cats, cuttlefish will try to eat other cuttlefish.
Classification
There are 119 species 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
eo:Sepio es:Sepia fr:Sepiida he:דיונון ja:イカ ko:갑오징어목 he:דיונון nl:Zeekat (inktvis) pl:Mątwy pt:Choco ru:Каракатица sl:Sipa zh:乌贼