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CLAM DISSECTION
CLAMS ARE:
Invertebrates- no backbone
Protostomesblastopore becomes mouth
determinate spiral cleavage
CLAM DISSECTION
KINGDOM ANIMALIA
___________
MOLLUSCA “Soft”
PHYLUM ____________
BIVALVIA
CLASS ______________
“2 shells”
(Pelecypoda)
UMBO tells direction
Anterior
Posterior
Dorsal
Ventral
http://biog-101-104.bio.cornell.edu/BioG101_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.k12.ar.us/massengale/mollusk_notes_b1.htm
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
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
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
Marine (salt water) clamsexternal fertilization
Freshwater clamsinternal 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%20webs/Clam-%20nervous%20system.htm