Phylum Molluska C-27-4

1. Soft bodies 2. Foot 3. Mantle 4. Shell 5. Visceral Mass Phylum Molluska 1. Soft bodies 2. Foot 3. Mantle 4. Shell 5. Visceral Mass

Classes Class Gastropod – One or no shelled - Snail and slugs Class Bivalvia – 2 shelled, clams. Oysters, scallops. Class Cephalopoda – Internal shell, octopus and squid, exception, one shells Natilius

I. Characteristics A. Coelomates – True coelom, a hollow fluid filled cavity surrounded by a mesoderm, body wall muscles are separated from the gut and can aid in blood transport. B. Trochophore – Larvae stage of mollusks and annelids.

Coelomate

Trochophore Larvae

D.Visceral Mass – Body area that contains all the mollusks organs Mollusca – body plan A. Foot is a soft muscular structure, used for movement. B. Mantle – Thin tissue that surrounds the body and secrete a calcium carbonate shell. C. Radula Is a Flexible tongue used for feeding by scrapping food off of leaves and plants. Present in snails and slugs D.Visceral Mass – Body area that contains all the mollusks organs

Mollusk Anatomy

Radula of a snail

a. Inner – smooth, protects soft body. E. Shell - also called valves and is secreted by the mantle. 1. 3 Layers a. Inner – smooth, protects soft body. b. middle- calcium carbonate, strength c. Outer – protects shell against sea environment.

Abalone shell layers

2. Feeding A. Much variation, carnivores, herbivores, filter feeders, detritus feeders, scavengers or parasites 3. Respiration A. Gills – Feathery structure that diffuse oxygen out of the water for aquatic mollusks to breath. B. Terrestrial mollusks usually exchange gas through a specialized adapted mantle cavity.

4. Circulation A. Open circulatory system- System that does not have vessel to transport circulatory fluid but transports the fluid to spaces where organs are bathed with nutrient filled fluid. B. Closed Circulatory System – Circulatory fluid is transported to organs through vessels.

5. Hemolymph – Circulatory fluid found in mollusks. 6. Hemocoel – Space where the hemolymph pools and is where organs are bathed.

Open C.S. Closed C.S.

5. Excretion A. Solid waste passes out through the end of the gut, anus. B. Niphridia - Nitrogen waste are removed from the blood by this organ. 6. Nervous systems A. Clams and relatives have few ganglia (cluster of nerves )and nerve cords. B. Octopus and relatives have well-developed brains, excellent vision, touch and taste 7. Reproduction A. Some mollusks are hermaphrodites, some external, some internal.

Nephridia of a Snail Nephridia

8. Classes: A. Gastropods 1. Examples – snails, slugs, abalone, sea hares nudibranchs 2. One shell is used for protection or no shell. 3. Torsion –process where the visceral mass twists bringing organs to the front of the animals body. 3. Non shelled animals use poison or are bad tasting

B. Bivalves 1. Examples – clams, oysters, mussels, and scallops 2. 2 shells present for protection 3. Adductor muscles - Shells are hinged together with these strong muscles. 4. Some produce nacre (mother of pearl)

5. Siphons – filter feeders use fleshy tubes that extend outside and between the shells. A. Incurrent siphon – Pulls water in filled with nutrients. B. Excurrent Siphon – Release waste.

Clam Siphons

6. Feeding in Bivalves A. Mucous Feeder – Clams use the mucous on their gills to trap food particles as water passes over them. Food is then transported to the mouth and to the stomach.

C. Cephalopods = “head” “footed” animals 1. Examples – chambered nautilus, octopus, squid, and cuttlefish. 2. Largest, most active and most intelligent 3. 8 tentacles and 2 arms = 10 appendages (squid, cuttlefish) - 8 arms (octopus) 4. Suckers found on tentacles along with teeth inside each sucker for gripping on to prey. 5. Internal shells or no shell, exception, (Nautilus) 6. Chromatophore pigment – pigment cam change to blend in to the surrounding. 7. Beak – powerful jaws for eating. 8. Ink – sac of ink released when threatened.

Squid eggs

Baby Squid

Giant Australia Cuttlefish