Cuttlefish
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Source: Allaboutnature.com
Cuttlefish are soft-bodied mollusks with short, flattened bodies
and a large head. Cuttlefish skin is soft and delicate, and
slides easily back and forth over an oval mantle of muscle that
is attached to the rigid, internal cuttlefish bone. It is covered
with chromatophores, or pigment sacs, which allow the cuttlefish
to change color for camouflage purposes, mating rituals and
to show emotions. Cuttlefish have eight sucker-lined arms that
are attached to the head in a ring around the mouth. They also
have skin flaps along each side, which shield two retractable
feeding tentacles that are longer than the rest and are flattened
at the end.
On the underbelly, there is a forward opening cavity that contains
the gills and openings for the gut, kidneys and sexual organs.
There is a siphon just beneath the head, which helps the cuttlefish
to steer and swim. Cuttlefish have large eyes with a W-shaped
lens and a transparent cover and lid. The body is edged by a
thin frill-like fin, which circles horizontally around the body.
Cuttlefish usually grow to between 5 to 30cm long, but the giant
cuttlefish grow much bigger. Giant cuttlefish are only found
in the waters off southern Australia and they produce cuttlefish
bones up to 1 meter long. Cuttlefish are usually only seen in
large numbers near the shore in winter, when they gather on
the shallow reefs to mate and spawn.
Cuttlefish eat fish, small mollusks (snails, clams, other cuttlefish,
etc.), worms, crabs, and shrimp. Prey are killed with a venomous
bite from the beak. However, cuttlefish are eaten by sharks,
fish and other cuttlefish. In order to escape predators, a cuttlefish
can squirt black ink into the water, allowing it to escape.
Another defense that cuttlefish have is changing their skin
color to blend into the background, camouflaging themselves.
While a squid’s internal shell is a transparent quill, cuttlefish
have an internal calcareous shell formed from spongy material,
which creates buoyancy. They have neutral buoyancy and can vary
their depth easily by changing the proportion of liquid to air
in their internal shell, the cuttlefish bones. Cuttlefish bones
or cuttlebones are the white, chalky, surfboard-shaped shells
that often wash up onto beaches. They are all that remains after
a cuttlefish has been attacked and eaten. The cuttlefish bone
also protects the internal organs and forms a framework against
which the muscles can pull. Calcium-rich cuttlefish bones, when
placed in bird cages, are a valuable source of calcium to the
bird. Cuttlefish bones can be ground into a fine powder that
can be used for polishing silver or even cleaning teeth. They
are also used by craft workers for sharpening fine instruments
and by silversmiths for making moulds for casting.
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