What do cuttlefish look like?
Cuttlefish are cephalopods, a class found within the phylum
Mollusca. Like other cephalopods, they have bilateral symmetry, a
prominent head, and their "foot" has been modified into a number of
arms and tentacles. They have internalized the shell found in most
mollusks, and it is referred to as the cuttlebone. Cuttlefish have
no backbone; they are invertebrates, and so, despite their
misleading name, they are not true fish. Protruding from around
their mouths, they have eight arms and two tentacles with which
they catch their prey.
One of the most remarkable aspects of cuttlefish, though, is
their advanced camouflaging abilities. Cuttlefish have very complex
eyes, with W-shaped pupils that can see the polarization of light
and in 3-D; they are, however, colorblind. Despite this, on natural
substrates, cuttlefish can change color in mere seconds to blend in
so well against their background that they are hardly visible. This
camouflage is done by means of a vast number of small neuromuscular
organs called chromatophores that expand and contract to change the
color of the cuttlefish' skin. Even after the cuttlefish has died,
the chromatophores may continue to cause color-change, in a
distinctive post-mortem pattern known as Wolkenwandern, or
"wandering clouds". There are also some other types of cells that
add to the variety of colors cuttlefish can display. Cuttlefish's
sides have been likened to a tv screen, so adept are they at
changing colors quickly and smoothly, and in fact, some tv screens
have been developed using a technology based on cuttlefish's
color-changing abilities.