Transcript File - Dr. Steve W. Altstiel

Dr. Steve W. Altstiel
Naples High School
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Phylum Molluska: over 100,000 species
Second-largest animal phylum.
Examples: chitons, clams, snails, slugs, and
squids.
Some of the shells are highly valued by collectors.
◦ From seashell collections we have learned much of what
we know about this group.
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Gastropods (snails)
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Bivalves (oysters, clams)
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Cephalopods (octopus)
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The foot is a muscular organ, shaped and used
differently by different species.
A clam uses its hatchet-shaped foot for digging.
Clams and oysters belong to the class
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A snail has a flat foot it uses for crawling.
◦ Because its stomach is in its foot, it is named
Gastropoda, “stomach foot”
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The foot in octopus and squids is modified into
many tentacles that are attached to the animal’s
head.
◦ Octopus and squids use their tentacles for moving and
for grasping and holding the prey they capture for food.
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The area of the mollusk called the “mantle”
makes the shell for the animal (if it has a
shell).
Mantle creates the colors and patterns on
the shells.
The shell is an exoskeleton, even though it is
completely surrounded by soft tissue in some
mollusks. Be cause the shell is continually
produced, it grows with the animal.
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Produces 8 separate plates that cover the
body.
◦ Have joints between each of these plates to allow
for it to curl up in a ball.
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Mantle in bi-valves make two distinct shells.
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Mantle in gastropods produce a single shell
in a sprial shape.
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Mantle cannot be seen, since it is the inner
layer of the shell.
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Yes, they do have a small shell.
◦ But the mantle is opposite and covers the shell
instead of being inside the shell.
◦ This shell is inside their bodies and is called a pen
(pen… ink… pen… ink)
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Nudibranchs or sea slugs are gastropods that
don’t produce a shell
Are all soft-bodied.
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Radula: rasplike tounge in the mollusk’s mouth.
Herbivorous (plant-eating) snails have a mouth
with radula containing many rows, each row with
five to seven complex teeth.
The snail uses its radula like a file, scraping off
small bits of food.
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Snails called cone shells are carnivorous (meateating) hunters that produce venom in glands
near the mouth.
Their radulas are shaped into long, hollow teeth,
which they thrust one at a time into their prey
like harpoons.
A barbed radular tooth fires through the
proboscis, an extension of the mouth.
It pierces the prey, paralyzing it with venom and
preventing its escape.
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C:\Documents and
Settings\marcella.williams\Desktop\Snail
Mouth.qtl
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The cone shell “swallows” the prey by engulfing it
with its proboscis.
Some snails produce a poison strong enough to
kill humans who handle them carelessly.
Their poison is a neurotoxin, one that attacks and
destroys nerves.
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The class of mollusks called Bivalves includes
clams, oysters, mussels, and scallops.
Foot size varies among marine bivalves.
Clams have a big hatchet-shaped foot for moving
about and for burrowing in mud or sand.
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Clams: large foot to dig deep in sand
Oyster (and mussels):small foot because these
animals attach themselves to hard objects early in
life and do not move around.
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Scallops don’t use their small foot to move around
either.
They swim by jet propulsion, clapping their shells
together and forcing water out the rim.
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Water enters and leaves a bivalve by way of two
tubes called siphons.
One siphon takes in water while the other
expels water and wastes.
Water taken in contains oxygen and food
particles consisting of detritus and plankton.
As the water flows across the gills, oxygen and
carbon dioxide are exchanged.
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Mucus on the gills traps microscopic food
particles, and tiny hair-like cilia on the gills move
the food-laden mucus toward the mouth.
Liplike structures called palps help sort the food
and direct it into the mouth.
Bivalves do not have a radula. The food
suspended in mucus moves through the
digestive organs, which break it down and
absorb it.
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In some bivalves, such as oysters, mantle tissue
secretes a pearly substance that coats any
irritating particles—bits of gravel, for example—
that lodge between the mantle and the shell.
As coats of this substance build up they form a
pearl.
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Bivalves such as clams, oysters, and scallops are
valuable as food;
They make up a major share of the marine
invertebrate cash crop.
Except for the shell, bivalves can be eaten whole.
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But when water in which they grow becomes
polluted with chemicals or disease organisms,
bivalves should not be eaten.
At certain times of year, for example, microscopic
organisms called dinoflagellates multiply rapidly in
the enclosed waters of bays and estuaries.
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When they grow so thick that the pigment in
their bodies makes the water look red, the
phenomenon is called a red tide.
Toxic substances produced by dinoflagellates
can concentrate in the clams and oysters that
use them as food.
Although the bivalves are not harmed, the toxin
attacks the nervous system of humans who eat
the clams and oysters.
This “paralytic shellfish poisoning” can be fatal
to humans
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Some people have died after eating just one
clam or mussel, others after eating many--each
with a small amount of poison.
You cannot tell whether the dinoflagellates are
present by looking at the water with your naked
eye.
Signs and symptoms of PSP most often occur
within 10 to 30 minutes after eating affected
seafood. Problems can include nausea, vomiting,
diarrhea, abdominal pain, and tingling or burning
lips, gums, tongue, face, neck, arms, legs, and
toes. Later problems may include shortness of
breath, dry mouth, a choking feeling, confused or
slurred speech, and lack of coordination.
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a specialized foot used in digging, grasping, or
creeping.
a mantle that covers the soft body, encloses the
internal organs, and, in many species, produces
a shell. Not all mollusks produce a shell.
a radula, which in most species is a rasp-like
scraping organ used in feeding.