Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes squid, octopuses, and nautiluses). Despite their common name, cuttlefish are not fish but molluscs. Recent studies indicate that cuttlefish are among the most intelligent invertebrate species.
The origin of the word cuttlefish can be found in the old English term cudele, itself derived in the 1400s from the Norwegian koddi (testicle) and the Middle German kudel (pouch), a literal description of the cephalopod's shape. The Greco-Roman world valued the cephalopod as a source of the unique brown pigment released from its siphon when alarmed. Hence, the word for it in Greek and Latin is sepia (later seppia in Italian).
Cuttlefish eat small molluscs, crabs, shrimp, fish, octopuses and other cuttlefish. Their predators include dolphins, sharks, fish, seals and other cuttlefish. Their life expectancy is about one to two years.