November 8, 2012
Cuttlefish: the Chameleon of the Sea
Sepia latimanus, common name cuttlefish, can be considered as one of the most uniquely evolved creatures of marine habitat. The species, despite their name, are not a fish, but molluscs. Cuttlefish are part of the order Sepia and belong to the class Caephalopods, which also includes squid, octopuses, and nautiluses. 'Cuttle' is a reference to a unique internal shell, the cuttlebone. As with all other mollusks, the cuttlefish has a calcium-based mantle which shapes the body, which is not unlike that of a jellyfish in ways other than appearance. The cuttlefish have eight arms, not unlike octopus, and two tentacles. Between these two tentacles is the mouth. The eyes of the cuttlefish, which vaguely resemble human eyes, extend from the front of the face. Cuttlefish's eyes are unable to detect color, yet it has the ability to change color in both degree and kind, making it easily surpass the abilities of a chameleon. The most stunning feature of cuttlefish is their skin. Cuttlefish skin is composed of three layers that have up to 200 pigment cells called chromatophores per square millimeter. The first and deepest skin layer is white in color to act as a light retracting base for the other layers. The middle layer produces blue, red, green, orange and even pink through the iridescent light reflecting cells inside the skin. The outer most layer consists of pigment cells that are like tiny disks of color which are too small to see. The layers of specialized skin also contain tiny plates of the protein chitin, called Iridophores, which are responsible for the light reflection. Cuttlefish camouflage is impressive not only because of the speed at which these animals can change patterns and colors but also because their camouflage is apparently very effective at deceiving the visual capabilities of their varied...