CLASS: BIVALVIA Phylum: Mollusca

Characteristics of Mollusks Commonly called shellfish Over 100,000 species Most are soft-bodied and have shells Most have bilateral symmetry

Mollusk Anatomy All Mollusks Have: 1. Muscular Foot: On the animal’s bottom, made of muscle, used for movement 2. Visceral Mass: A soft, fleshy body located above the foot, and containing guts, heart, and other internal organs

Mollusk Anatomy All Mollusks Have: 3. Mantle: Covers the body and is responsible for secreting a shell in most species 4. Radula: Raspy tongue common to most mollusks (not bivalves). Has rows of teeth to scrape bacteria and algae off of rocks

Mollusk Anatomy Most mollusks breathe with the help of gills

Three Classes of Mollusks 1. Bivalvia- clams, mussels, scallops 2. Gastropods- snails, sea slugs 3. Cephalopods- Squid, Octopus, Cuttlefish, Nautilis

Bivalves: Scientific Classification Kingdom: Animalia Phylum: Mollusca Class: Bivalvia CLAMS!

Bivalve Characteristics Have two shells (valves) Mostly sessile (non- moving) and filter feeders Have no head or radula

Bivalve Characteristics Held together by a hinge ligament When threatened, the bivalve can “clam up” using its adductor muscles The umbo is the oldest part of the shell, growth occurs in concentric rings around it

Bivalve Characteristics Has two siphons  One carries water in, the other pumps water out  Receives oxygen and food  Eliminates Waste

Bivalve Locomotion Most bivalves move by expansions and contractions of the foot.  Clams vs. The World! Clams vs. The World! Scallops swim by clapping their shells together.  Scallop Swimming Scallop Swimming

Bivalve Locomotion Oysters and mussels usually are sessile (don’t move) and attach to substrates with byssal threads.

Bivalve Reproduction External Fertilization- sperm and egg released into the water Larva hatches and develops in the water

Famous Bivalves: Shipworms Shipworms are highly destructive Bore into mangrove roots, driftwood, wooden boats The valves have tiny teeth that act as wood rasps and allow these bivalves to burrow through wood. They feed on wood particles with the help of bacteria.

Famous Bivalves: Oysters Oysters can produce pearls Pearls are formed when the oyster secretes shiny layers of calcium carbonate to coat irritating particles or parasites lodged between the mantle and the inner surface of the shell  SciShow: Pearls SciShow: Pearls

Famous Bivalves: Scallops Have a row of small blue eyes along the mantle edge. Each eye has a cornea, lens, retina, and pigmented layer. The Giant Clam also has eyes! Giant Clam

Clam Anatomy