The document summarizes key information about bivalves, including their anatomy, habitat, feeding, reproduction, pearl formation, and internal anatomy. Bivalves have two shells held together by adductor muscles, gills for oxygen intake from water, and a mantle that secretes their shell. Most bivalves are sessile filter feeders that live on or burrow into the seafloor, though some like mussels and scallops can attach or swim. They have separate sexes and external fertilization and development. Pearls sometimes form as a protective response in oysters.

1. The Bivalves
Phylum Mollusca

2. Anatomy
• Two shells (valves)
held together tightly
by adductor muscles
• No head, brain is a set
of nerve cells (ganglia)
• Gills to take oxygen
from water
• Mantle secretes the
shell
• Bilateral symmetry

3. Class Bivalvia – The Bivalves
(clams, mussesls, scallops, oysters)

4. Habitat
• Benthic
– Most Sessile, few motile
– Infauna – most burrow
down
– Epifauna – some live on
seafloor
• Mussels attach with
byssal threads
• Scallops swim by
clapping shells together

5. -Most are planktivores
-Incurrent & excurrent
Siphons
Feeding
-Important filter
feeders-up to 25
gallons of water/day

6. Bivalve Reproduction
-Separate sexes
-External
fertilization
and
development

7. Pearl Formation
• Mostly in oysters
• Protection against
parasites or grains
of sand
• Often not round
• Natural pearls are
more costly
• Cultured pearls are
made by inserting
an object in the
oyster

9. Clam Internal Anatomy