CLAM DISSECTION

http://www.jburroughs.org/science/resources/Clam/clam10.html

CLAMS ARE:

Invertebrates-

no bones around nerve cord

Protostomes-

blastopore becomes mouth

determinate spiral cleavage http://www.zo.utexas.edu/faculty/sjasper/images/so28_04.gif

Clam & octopus from: http://www.geocities.com/TheTropics/2428/directory.html

CLAM DISSECTION

KINGDOM ___________

PHYLUM ____________ “Soft”

CLASS ______________ “2 shells”

ANIMALIA

MOLLUSCA

BIVALVIA

(Pelecypoda)

UMBO tells direction

Anterior

Posterior

Dorsal

Ventral

Image by Riedell/Vanderwal © 2005

Clams are SESSILE

as ADULTS

Don’t move much

Stay in one place

LARVA

swim with

CILIA

http://seagrant.gso.uri.edu/factsheets/fsquahog.html

http://www.okc.cc.ok.us/biologylabs/Images/Evolimages/trochophore.JPG

NO CEPHALIZATION (No head)

Shell = valve (Bivalvia = 2 shells)

Growth rings - increase with age

http://wwwbio200.nsm.buffalo.edu/labs/tutor/Clam/

ADDUCTOR MUSCLES

Turn POSTERIOR END toward door Cut your adductor muscles to open shell

Image from: http://sps.k12.ar.us/massengale/mollusk_notes_b1.htm

ANTERIOR & POSTERIOR ADDUCTORS

FOOT – points toward anterior end

VISCERAL MASS Contains heart, digestive, excretory, reproductive

Mantle cavity (NOT COELOM)

NO cephalization

Gills hang OUTSIDE body in mantle cavity

Image from: http://sps.k12.ar.us/massengale/mollusk_notes_b1.htm

Image modified from: http://www.lander.edu/rsfox/310images/310molluscImage.html

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/unit5/invertebrate/menu.html

http://js082.k12.sd.us/My_Classes/Advanced_Biology/Ch_25/Clam%20Dissection/Clam_Dissection.htm

Mantle produces shell (calcium carbonate makes it hard)

INCURRENT & EXCURRENT

SIPHONS

CILIA on gills pull in water

move food

up toward

mouth

Image by: Riedell/VanderWal © 2005

SEXUAL REPRODUCTION

SEPARATE SEXES

Male & female clams

General term for reproductive organs

= GONADS

SEXUAL REPRODUCTION Marine (salt water) clams-

external fertilization

(sperm or eggs exit through siphon)

Freshwater clams-

internal fertilization (sperm enters through siphon; fertilized eggs/larva exit )

Other mollusks

GASTROPODS- internal fertilization

Land snails = hermaphrodites

Aquatic snails = 2 separate sexes

CEPHALOPODS- internal fertilization

Separate sexes –

http://www.geocities.com/TheTropics/2428/directory.html

Indirect development TROCHOPHORE LARVA

Ciliated- can swim

ADULTS-

Sessile = stay in one place

Can put out foot and crawl

http://www.okc.cc.ok.us/biologylabs/Images/Evolimages/trochophore.JPG

GILLS Trap food (PALPS move it forward)

Ridges for more surface area

(like typhlosole)

Gas exchange

Diffusion moves

oxygen & CO2 across membrane

GAS EXCHANGE IN GILLS

Image by Riedell

Diffusion moves from HIGH → LOW

OPEN CIRCULATION

• Blood flows loose inside coelom

and tissue spaces

• Heart pumps blood (HEMOLYMPH)

• COELOM = SMALLER

mainly around heart

= pericardial cavity

OPEN CIRCULATION is less efficient way of moving oxygen,

nutrients, and nitrogen waste

1. Doesn’t go directly to parts

2. High oxygen and low oxygen blood can

mix so it gets diluted

HEART & PERICARDIAL CAVITY

DIGESTIVE • FILTER FEEDERS (strain food from water)

• Food pulled in through incurrent siphon by

cilia moving on gills

• Food trapped in mucous on gills

• Palps move food up and into mouth

esophagus stomach

Digestive

gland

Intestine anus

DIGESTIVE GLAND

Makes BILE to break down fat

Finishes digestion

http://wwwbio200.nsm.buffalo.edu/labs/tutor/Clam/

INTESTINE

carries digestive waste to anus

http://www.jburroughs.org/science/resources/Clam/clam10.html

3 Body systems use mantle cavity

EXCRETORY - Nitrogen waste from kidney

DIGESTIVE – feces released from anus

REPRODUCTIVE-

Sperm or egg (if external fertilization)

Larva (if internal fertilization)

Image from: http://sps.k12.ar.us/massengale/mollusk_notes_b1.htm

NERVOUS SYSTEM

3 pairs of ganglia

2 pairs of nerve cords

http://www.student.loretto.org/zoology/Graphic%20webs/Clam-%20nervous%20system.htm