Cephalopods are mollusk of the class Cephalopoda, which includes squid, cuttlefish, octopus, nautiloids etc. Cephalopods are invertebrate marine animals that possess streamlined soft bodies, a large head and eyes, and numerous feet (called arms or tentacles) which is about eight or ten in most forms but about 90 in Nautilus. There are several species (about 800) of Cephalopods. Cephalopods have a more oxygen-efficient closed circulatory system, and they are well-adapted to fast swimming in the pelagic zone of the ocean.
