Cuttlefish

Cuttlefish

Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda, which also includes squid, octopuses and nautiluses. 'Cuttle' is a reference to their unique internal shell, the cuttlebone. Despite their name, cuttlefish are not fish but molluscs.

The cuttlefish has a lot of interesting behavior. The animals change color and body pattern not only for camouflage, but also in reproductive behavior. The males, for instance, show each other their arm stripes and darken their faces when they compete for dominance. Males will go through the same routine when they see their reflection in a mirror.

Although it is invisible to us, they can produce patterns of polarized light, apparently at will. When threatened, they can suddenly produce false eye spots that are plainly visible and frankly ominous. And they can also squirt ink like their cousins the squid and octopus.

Know more:
http://en.wikipedia.org/wiki/Cuttlefish