Phylum Mollusca Soft-bodied animals Internal or external shell Include snails, slugs, clams, squids and octopi Trochophore: free-swimming larval stage of an aquatic mollusk
True coeloms Have complex organ systems
Foot: muscular part of a mollusk Mantle: thin layer of tissue that covers most of a mollusk s body
Shell: structure in mollusks made by glands in the mantle that secrete calcium carbonate Visceral mass: area beneath the mantle of a mollusk that contains the internal organs
Herbivorous Carnivores Filter feeders Detritivores Parasites Radula: flexible, tongue-shaped structure used to capture food by snails and slugs Siphon: tube-like structure through which water enters and leaves the body, capturing plankton in the process
Gills inside their mantle cavity Land snails respire using a mantle cavity lined with blood vessels Typically live in moist places to keep this lining wet
Open circulatory system: blood is pumped through vessels by a simple heart Works well for slow-moving mollusks such as snails and clams (demands for oxygen are low) Closed circulatory system: can transport blood through an animal s body much more quickly
Cells of the body release nitrogencontaining waste into the blood in the form of ammonia Nephridia remove ammonia from the blood and release it out of the body
Complexity of the nervous system varies greatly between mollusks Clams and other two-shelled mollusk lead inactive lives simple nervous system
Octopi and their relatives are active and intelligent predators most highly developed nervous system of all invertebrates Capable of complex behavior, such as opening a jar to get food inside
Move in many different speeds Snails secrete mucus and move slowly over the surface using a rippling motion of the foot Octopus uses a form of jet propulsion, drawing water into its mantle and forcing it out the siphon
Reproduce in many different ways Snails and two-shelled mollusk reproduce sexually by external fertilization Some mollusk are hermaphrodites
Gastropods Shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side
Gastropods Shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side Bivalves Have two shells that are held together by one or two powerful muscles
Gastropods Shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side Bivalves Have two shells that are held together by one or two powerful muscles Cephalopods Soft-bodied mollusks in which the head is attached to a single foot; the foot is divided into tentacles or arms
Feed on plants, prey on animals, and clean up their environment by filtering algae out of the water or by eating detritus Filter-feeding bivalves can be used to monitor water quality Serve as subjects of biological research
Mollusks Coelomates; bilateral symmetry, cephalized Soft body called mantle, which secretes material that often becomes shell Three major classes: Gastropods (i.e. snails & slugs) Bivalves (i.e. clams & oysters) Cephalopods (i.e. squid, octopus, cuttlefish, nautiluses) There are over 128,000 species of living mollusks. Each tentacle on a octopus has 240 suction cups to grasp its prey. Mollusks can be found from the deepest ocean floor to the intertidal zone, in freshwater, & everywhere on land. Most cephalopods can release ink to distract enemies while they swim away. Some oysters may release over one million eggs in a season. Only about one of these eggs will survive to become an adult oyster. The Giant Pacific Octopus can grow up to 30 feet. Many land snails can lift 10 times their own weight up a vertical surface.