Cephalopods

General Characteristics  Cephalopoda means "head foot" –Cephalopods are characterized by a completely merged head and foot  Octopuses, squids, cuttlefish, and chambered nautiluses  Well developed head  Prominent foot divided into tentacles  Free swimming  Predatory - carnivorous  Strong suckers  A cephalopod is also characterized by a horny beak secreted by the walls of the buccal cavity, and a radula within the buccal cavity.  The digestive tract consists of three parts: esophagus, which may contain a crop; stomach, which mashes food; and caecum, where most digestion and absorption occur esophagusstomachcaecumesophagusstomachcaecum

Characteristics  Closed circulatory system –Blood circulates entirely within blood vessels –Allows for high metabolic rate  Reproduction –A female typically possesses a single oviduct. A male produces spermatophores that it transfers to the female's genital pore by means of a specialized arm or tentacle. In some species, the specialized arm tip may be pinched off and left in the female's mantle cavity –Mating in some cephalopods includes courtship rituals that may consist of color changes, body movements, or combinations of both.

Squid  Marine  Largest invertebrate (20 M; 3,360 Kg)  Large complex brain  Highly developed nervous system  Large pair of vertebrate like eyes  Two Tentacles and Eight Arms –Tentacles are used to capture prey –Arms force prey into mouth

Squid  Muscular mantel  propels by pumping water through siphon –Jet Propulsion –a very energy-consuming way to travel compared to the tail propulsion used by fish  This inefficiency in locomotion worsens as the size of the species increases  This is probably the reason why many species will use their fins or arms for locomotion if possible –can move short distances in any direction by rippling of a flap of muscle around the mantle muscle  Excrete inky substance when threatened  Chromatophores - change color –Used for communication and camouflage

Squid  Internal fertilization –Lay mass of gelatinous encased eggs –Maternal protection until hatching

Cuttlefish   Cuttlefish have an internal shell (the cuttlebone)shellcuttlebone   large W-shaped pupilspupils   eight arms & two tentacles furnished with denticulated suckers, with which they secure their prey.armstentacles

Cuttlefish   Their life expectancy is about one to two years.   Recent studies indicate that cuttlefish are among the most intelligent invertebrates.   Cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates.

Octopuses  The Common Octopus reaches 24 – 36 inches in length.  Habitat - The Common Octopus is found world-wide in tropical, subtropical and temperate waters. It prefers coastal waters, and can live both in the shallows and down to a depth of 500 feet temperate  The skin is smooth and has special pigment cells, chromatophores, that make it possible for the octopus to blend in with the surroundings (camouflage). –Coloration can also reflect its mood. –White is for fear, red is for anger and brown is the usual color. and brown is the usual color.  lack any internal shell

Octopuses  The Common Octopus is normally solitary and territorial. It finds a home in a cavity or digs a burrow for itself, and leaves it only to feed or reproduce. They often protect and hide their homes with shells, stones and other solid things that they gather. solitary  The Common Octopus is an active nocturnal predator that feeds mainly on crustaceans, fish and bivalves. predator

Octopuses  Octopuses have the most complex brain of all the invertebrates. Just like vertebrates, they have long term and short-term memories invertebrates –They learn to solve problems by trial-and- error and experience

Chambered Nautilus  Most primitive of the Cephalopods  Size – 8 to 10 inches  Found in the Indian and Pacific Oceans down to 1800 feet in tropical regions  The chambered nautilus is an example of an a living fossil, it has remained unchanged for over 400 million years  Jet propulsion propels the nautilus in the opposite direction at high speeds.  Nocturnal

Chambered Nautilus  The shell of the nautilus is comprised of many individual chambers. Each chamber is individually sealed and contains an amount of gas. –This provides the animal with buoyancy. –The nautilus can regulate its density by injecting or removing fluid into these chambers through a system of tubes.