CLAM DISSECTION CLAMS ARE Invertebrates no backbone Protostomes

CLAM DISSECTION

CLAMS ARE: Invertebrates- no backbone Protostomes- blastopore becomes mouth determinate spiral cleavage

CLAM DISSECTION ANIMALIA KINGDOM ______ MOLLUSCA PHYLUM ______ “Soft” BIVALVIA CLASS _______ “ 2 shells” (Pelecypoda)

UMBO tells direction Anterior Posterior Dorsal Ventral http: //biog-101 -104. bio. cornell. edu/Bio. G 101_104/tutorials/animals/clam. html

NO CEPHALIZATION (No head) Shell = valve (Bivalves = 2 shells) Growth rings Adults = sessile (stay in one place)

ADDUCTOR MUSCLES Turn POSTERIOR END toward door Cut your adductor muscles to open shell Image from: http: //sps. k 12. ar. us/massengale/mollusk_notes_b 1. htm

Mantle cavity (NOT COELOM) Image from: http: //sps. k 12. ar. us/massengale/mollusk_notes_b 1. htm NO cephalization Gills hang OUTSIDE body in mantle cavity

Hinge Teeth on dorsal edge lock to keep shells from sliding

Smooth lining Irritants are coated by mantle to protect soft body “Pearls” Animation from: http: //vilenski. org/science/notebook/unit 5/invertebrate/menu. html

Mantle produces shell (calcium carbonate makes it hard)

INCURRENT & EXCURRENT SIPHONS move food up toward mouth CILIA on gills pull in water

Image by: Riedell/Vander. Wal 2005

SEXUAL REPRODUCTION SEPARATE SEXES Male & female clams Marine (salt water) clams external fertilization Freshwater clams internal fertilization (sperm enters through siphon)

Other mollusks GASTROPODS- internal fertilization Land snails = hermaphrodites Aquatic snails = 2 separate sexes CEPHALOPODS- internal fertilization Separate sexes –

Indirect development TROCHOPHORE LARVA Ciliated- can swim ADULTS- Sessile = stay in one place Can put out foot and crawl

GILLS Trap food (PALPS move it forward) Ridges for more surface area (like typholosole) Gas exchange Diffusion moves oxygen & CO across membrane

GAS EXCHANGE IN GILLS H i

ANTERIOR & POSTERIOR ADDUCTORS

FOOT – points toward anterior end

VISCERAL MASS Contains heart, digestive, excretory, reproductive

OPEN CIRCULATION • Blood flows loose inside coelom and tissue spaces • SMALLER Coelom = pericardial cavity (space around heart)

OPEN CIRCULATION is less efficient way of moving oxygen, nutrients, and nitrogen waste 1. Doesn’t go directly there 2. High oxygen and low oxygen blood can mix so it gets diluted

HEART & PERICARDIAL CAVITY

DIGESTIVE • Food pulled in through incurrent siphon by cilia on gills • Food trapped in mucous on gills • Palps move food up and into mouth Digestive gland esophagus stomach Intestine anus

ALL Released into Mantle cavity/ exit via excurrent siphon • Nitrogen waste from kidney • Digestive waste from anus • Sperm or egg (if external fertilization) • Larva (if internal fertilization)

NERVOUS SYSTEM 3 pairs of ganglia 2 pairs of nerve cords http: //www. student. loretto. org/zoology/Graphic%20 webs/Clam-%20 nervous%20 system. htm