1. Phylum Mollusca
Head, visceral mass, muscular foot, and thin mantle that covers the body and secretes the shell
Class Gastropoda:
snails and limpets
Class Bivalvia (Pelycypoda):
mussels and clams

2. Gastropoda

3. Aquatic Gastropoda In N.S. 15 families, ~500 species Two suborders
Prosobranchia-gilled snails
Pulmonata-lunged (pouch) snails
Mouth has a radula, a ribbon of rasping teeth
Gilled snails have operculum (trap door cover)
Sinistral
Dextral

4. Natural History Most are scrapers
Gilled snails respire by an internal gill
Pulmonate snails have a pouched gill; many come to surface to breathe surface air, hence can tolerate low oxygen conditions
Reproduction: most gilled snails have separate sexes; most pulmonates are hermaphroditic
Egg masses often resemble blobs of mucous
Development is within the egg; hatch as small snails with only 1-2 whorls (most adults have 3-4)
Some are intermediate hosts for human parasites
Are food for many aquatic vertebrates (crush) and invertebrates (invade)
Bioindicator status:
Gilled snails-sensitive to facultative
Pulmonate snails-most are tolerant

5. Bivalvia ~270 freshwater species in N.A.
Two shells connected by strong hinge ligament

6. Anatomy

7. Bivalve Natural History
Most abundant and diverse in moderate current in medium to large rivers;
US is center of origin
Intolerant of siltation and low oxygen
All are filter feeders of suspended algae, bacteria, and detritus
Filtering mechanism doubles as a gill

8. Glochidium-for dispersal, not nutrition
Reproduction
Glochidium-for dispersal, not nutrition

9. Species of Note
Fingernail clams release large, developed young; this smallest of clams produces the largest of eggs and juveniles
Asian Clam-introduced;
1st observed in 1938
Cannot tolerate cold

10. Zebra Mussels, Dreissena polymorpha

11. Veliger

12. http://fl. biology. usgs

13. Cracking Pearlymussel
Endangered Unionids
Northern Clubshell
Cracking Pearlymussel
White Wartyback
Fat Pocketbook
Rough Pigtoe