Molluscs
belonging to the class Cephalopoda and the order Sepiida, they are
most closely related to squid, octopuses and nautiluses. With eight
arms, two tentacles with denticulated suckers used for securing prey
and large W-shaped pupils and being named for their unique internal
shell, the cuttlebone. They generally range in size from 15-25cm,
while the largest species, Sepia apama, can reach 50cm in mantle
length and over 10.5kg in mantle weight.
Cuttlefish
have the one of the largest brain-to-body size ratios in the world
and recent studies show them to be amongst the most intelligent
invertebrates. Eating other cuttlefish, small molluscs, crabs,
shrimp, fish, octopuses and worms. Their predators include dolphins,
shark, fish, seals, sea birds and other cuttlefish. Their life
expectancy is generally one to two years.
The
cuttlebone that cuttlefish are so famous for is a porous structure
formed of aragonite, that provides the cuttlefish with buoyancy,
which it regulates by altering the gas-to-liquid ratio in the
chambered cuttlebone with the ventral siphuncle.
Often
referred to as the chameleons of the sea, cuttlefish have the
remarkable ability to change the colour and texture of their skin to
communicate with other cuttlefish, camouflage themselves and as a
deimatic display to warn off potential predators. This colour
changing ability is produced by groups of blue, red, yellow, black
and brown pigmented chromatophores above a layer of reflective
iridophores and leucophores. With up to 200 of these specialized
pigment cells per square millimeter, this would be equivalent to
about 359DPI if they were individually controlled.
Even
though they lack the ability to perceive colour, cuttlefish are able
to rapidly change the colour of their skin to match their
surroundings, even in complete darkness, through some mechanism which
is not yet understood.
The
Greco-Roman world valued cuttlefish for the unique brown pigment
which they release when attacked, which they called sepia, a word
still used in modern english to refer to a brown pigment. The
cuttlebone on the other hand was traditionally used by jewellers and
silversmiths as moulds for small objects, and more recently as a
source of dietary calcium for parakeets and other caged birds.
Very interesting piece! Why did yoiu write it? Did you see one? How do they relate to their environment? Are the edible? And what are denticulated suckers? What are chromatophores and all that other stuff to which you referred? Are there intelligent invertebrates? What are they?
ReplyDeleteclick on the links it will make much more sense that way.
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