Cuttlefish
Cuttlefish have an internal shell, large eyes, eight arms and two tentacles furnished with denticulated suckers, by means of which they secure their prey. These tentacles can be retracted completely into the body. They possess an internal structure which is very porous and composed of calcium carbonate. The maximum mantle length is generally 45 cm, although one individual has been recorded at 60 cm. The mantle (main body area above the eyes) houses the cuttlebone, reproductive organs, and digestive organs. The cuttlebone provides 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. The cuttlebone is divided into tiny chambers in which the cuttlefish can fill or empty of gas. Each species has a distinct shape, size, and pattern of ridges or texture on the "bone". The cuttlebone is unique to cuttlefish, one of the features contrasting them with their squid relatives. A pair of flat fins span the entire length of the mantle, and they undulate rapidly when the cuttlefish swim. The head is located at the base of the mantle, with two large eyes on either side and a beaklike jaw in the center. Adults can be recognized by the white lines branching from the base of the flared third arms.
The amazing European or common cuttlefish, Sepia officinalis , are sometimes called the chameleon of the sea because of their remarkable ability to rapidly alter their skin color at will. This skin flashing allows them 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, 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 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 marine animals who can also sense polarization.
Cuttlefish eyes are among the most developed in the animal kingdom. They have similar eyes to humans, although they cannot see color. Like other cephalopods they can perceive the polarization of light, which essentially enhances their perception of contrast. They have two spots of concentrated sensor cells on their retina known as fovea. One is used to look forward, and one to look backwards.
Cuttlefish have ink, like squid and octopuses. Their predators are sharks, monkfish, swordfish, and other cuttlefish. They live about 1 to 2 years.
Encounters
Cuttlefish are found in the Mediterranean, North and Baltic Seas, although populations have been proposed to occur as far south as the South Africa. They are also found in sublittoral depths, at around 200 m.
Diet
Their highly specialized array of color-changing structures allow it to blend itself perfectly into the background. This lets it sneak up on prey and shoot out its two long tentacles at lightning speed, which have suckers on the widened pads at the tips. It uses these suckers to grab a hold of its prey and bring it back towards its beak. Cuttlefish eat small mollusks, crabs, shrimp, fish, and other cuttlefish.
Reproduction
The reproductive cycles of cuttlefish occur year round, especially during the months of March and June. Cuttlefish have separate male and female sexes. The males transfer sperm to the females via a hectocotylized arm (an arm modified for mating). Cuttlefish have large eggs, 6-9 mm in diameter, that are stored in the oviduct, which are then deposited in clumps on the bottom of the sea. The eggs are colored with ink, which helps them to better blend into the background. The young hatch with a nutritious yolk that will support them until they are able to secure food for themselves. They hatch at a much further developed stage than an octopus does and immediately start feeding on suitably small shrimps.
Captivity
Like octopuses, cuttlefish have been successfully raised as pets in home aquariums, even though they demand intensive attention to maintenance. Domestic cuttlefish are oddly reminiscent of domestic cats even exhibiting cat-like behaviors such as resting, pouncing on moving prey, begging owners for food (even 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.
There are 119 species currently recognized. They are grouped into 5 genera.
CLASS CEPHALOPODA
- Subclass Nautiloidea: nautilus
- Subclass Coleoidea: squid, octopus, cuttlefish
- Superorder Octopodiformes
- Superorder Decapodiformes
- Order Spirulida: Ram's Horn Squid
- Order Sepiida : cuttlefish
- Family Sepiadariidae
- Family Sepiidae
- Order Sepiolida: bobtail squid
- Order Teuthida: squid