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CLAM DISSECTION
http://www.jburroughs.org/science/resources/Clam/clam10.html
CLAMS ARE:
Invertebratesno bones around nerve cord
Protostomesblastopore 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 ANIMALIA
___________
MOLLUSCA “Soft”
PHYLUM ____________
BIVALVIA
CLASS ______________
“2 shells”
(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
http://seagrant.gso.uri.edu/factsheets/fsquahog.html
LARVA
swim with
CILIA
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)
Image from: http://sps.k12.ar.us/massengale/mollusk_notes_b1.htm
NO cephalization
Gills hang OUTSIDE body in mantle cavity
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
move food
up toward
mouth
CILIA on gills pull in water
Image by: Riedell/VanderWal © 2005
SEXUAL REPRODUCTION
SEPARATE SEXES
Male & female clams
General term for reproductive organs
= GONADS
SEXUAL REPRODUCTION
Marine (salt water) clamsexternal fertilization
(sperm or eggs exit through siphon)
Freshwater clamsinternal 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
http://www.okc.cc.ok.us/biologylabs/Images/Evolimages/trochophore.JPG
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 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
http://wwwbio200.nsm.buffalo.edu/labs/tutor/Clam/
DIGESTIVE GLAND
Makes BILE to break down fat
Finishes digestion
http://www.jburroughs.org/science/resources/Clam/clam10.html
INTESTINE
carries digestive waste to anus
3 Body systems use mantle cavity
EXCRETORY - Nitrogen waste from kidney
DIGESTIVE – feces released from anus
REPRODUCTIVESperm 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