• Examples: snails, slugs, clams, oysters, octopuses• Most of these animals live in the ocean.• Most mollusks fit into 3 classes: – Gastropods: includes slugs and snails – Bivalves: includes clams and other shellfish with 2 shells – Cephalopods: includes squids and octopuses
• How Do Mollusks Eat? – Snails and slugs eat with a ribbonlike organ —a tongue covered with curved teeth called a radula. – Clams and oysters attach to one place and use gills to filter tiny plants, bacteria, and other particles from water – Octopuses and squids use tentacles to grab their food and place it in their powerful jaws.
• Ganglions and Brains – Special ganglia control breathing, movement, and digestion. Octopuses and squids have the most advanced nervous system – Cephalopods are thought to be the smartest invertebrates
The Colossal Squid (Mesonychoteuthis hamiltoni, from Greek mesos (middle), nychus (claw), and teuthis (squid)), sometimes called the Antarctic or Giant Cranch Squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis. Though it is known from only a few specimens, current estimates put its maximum size at 12–14 metres (39–46 feet) long, based on analysis of smaller and immature specimens, making it the largest known invertebrate.
• Pumping Blood – Open circulatory system: circulatory fluid is not contained entirely within the vessels – Closed Circulatory System: heart circulates blood through a network of blood vessels that form a closed loop
• Mollusk Bodies – Mollusks are known for their broad, muscular foot. The foot helps the animal move. In gastropods, the foot makes mucus that the animal slides along. – The gills, gut, and other organs form the visceral mass. It lies in the center of a mollusk’s body. – A layer of tissue called the mantle covers the visceral mass. The mantle protects the bodies of mollusks that do not have a shell. – In most mollusks, the outside of the mantle secretes a shell, which protects it from predators and from drying out.
• Often called segmented worms because their bodies have segments.• A segment is an identical, or almost identical, repeating body segment.• Have bilateral symmetry, but are more complex• Have a closed circulatory system and a complex nervous system with a brain.• A nerve cord connects the brain to a ganglion in each segment.
• Earthworms – Most familiar annelid worm – Has 100 to 175 segments – Eat material in soil and leave behind wastes called castings. – Earthworms improve garden soil by digging tunnels. – To move, earthworms use stiff hairs, or bristles, on the outside of their body.
• Marine Worms – Called polychaetes, which means “ many bristles” – They are covered in bristles and come in many colors – Most of these worms live in the ocean. – Some eat mollusks and other small animals, or filter small pieces of food from the water
• Leeches – Known as parasites that suck other animals’ blood – Some are scavengers that eat dead animals, others are predators that eat insects, slugs, and snails. – Leeches are sometimes used after surgery to prevent dangerous swelling near a wound. – Doctors can use a chemical in leeches that encourages blood flow to prevent blood clots.