CLAM DISSECTION

CLAMS ARE:

Invertebrates- no backbone

Protostomes- blastopore becomes mouth

CLAM DISSECTIONKINGDOM ___________

PHYLUM ____________ “Soft”

CLASS ______________ “2 shells”

ANIMALIA

MOLLUSCA

BIVALVIA (Pelecypoda)

UMBO tells directionAnteriorPosteriorDorsalVentral

NO CEPHALIZATION (No head)

Shell = valve (Bivalves = 2 shells)

Growth rings

Adults = sessile (stay in one place)

ADDUCTOR MUSCLES

Turn POSTERIOR END toward doorCut your adductor muscles to open shell

Mantle cavity (NOT COELOM)

NO cephalizationGills 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”

Mantle produces shell (calcium carbonate makes it hard)

INCURRENT & EXCURRENTSIPHONS

CILIA on gills pull in water

move food up toward mouth

SEXUAL REPRODUCTIONSEPARATE SEXES

Male & female clams

Marine (salt water) clams- external fertilizationFreshwater 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 developmentTROCHOPHORE 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 & carbon dioxide

across membrane

GAS EXCHANGE IN GILLS

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

• Reduced Coelom = pericardial cavity

(space around heart)

PROBLEMS with OPEN CIRCULATION

Less efficient way of moving oxygen & nutrients to muscles (and removing Nitrogen wastes).  

High oxygen and low oxygen fluids mix so muscles can’t function as efficiently

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

esophagus stomach

Digestive gland

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%20webs/Clam-%20nervous%20system.htm