Download mantle (secrets shell)

PHYLUM MOLLUSCA
Second largest phylum behind Arthropoda
General characteristics:
- soft bodies enclosed in
a calcium carbonate shell
- mantle (secrets shell)
- unsegmented, bilateral symmetry
- muscular foot – locomotion
- gills
- complete digestive tract
- open circulatory system
- usually separate sexes
- cephalization (having a head)
- many are benthic
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1. Class: Gastropoda (stomach foot) or Univalvia (one shell)
Spanish Dancer
ex: snail, abalone, conch, limpet,
nudibranch (no shell)
Their bodies are covered by one shell,
except for the nudibranch.
Most are benthic herbivores, although
the dog whelk is carnivorous.
Special tongue (radula) with a ribbon of flexible teeth on its surface
works like a mini-chain saw. It is used to scrape surfaces for algae
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or to cut into other shells.
Figure 7.19
2. Class: Pelecypoda (hatchet foot) or Bivalvia (two shells)
ex: clams, oysters, scallops
- enclosed in 2 shells(lined by mantle)
- body laterally compressed
- no radula
- benthic planktivores
- gills also filter small food particles
- filter seawater through incurrent
& excurrent siphons
Swimming Bivalves
- some are sessile (oyster)
others swim by opening and
closing both shells (scallop)
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CLAM DISSECTION
Internal Structure of the Clam - Part
IInternal Structure of the Clam - Part II
Internal Structure of the Clam - Part III
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3. Class: Cephalopoda (head foot) is the basic body plan for squid,
octopus, cuttlefish, and chambered nautilus
- the most advanced brain of all invertebrates
- complex nervous system / large eyes / excellent vision
- foot modified into arms and tentacles
- squid has an internal shell (pen) that is clear and flexible
- protected by thick muscular mantle
-excellent swimmers –
jet propulsion
- hunters
The only hard part of
their body is their beak.
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- mouth has a sharp beak for eating worms, fish, etc.
- moves by jet-propulsion, mantle fills with water which can be
squirted out to propel them backwards
-chromatophores in the skin change colors when the animal is
alarmed and for camouflage
-Octopus
-Dwarf Cuttlefish
-Cuttlefish
- ink gland is used as a “smoke screen” for a quick escape
- eyes have a cornea, lens and retina; excellent vision
In the octopus, reproduction is by
internal fertilization. During the 30
days until hatching, the female
carefully aerates, cleans and watches
the eggs - never leaving - even to eat.
The female usually dies from
exhaustion and starvation soon
after they hatch.
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A soft, flexible body (no shell) allows the octopus to hide in very small
spaces.
They are very shy creatures and do not attack humans nor eat
ships! In captivity, they seek out human contact.
Beak-like jaws, secrete paralyzing substance, some have toxic bite
The octopus’ head has 8 regenerative arms, thus the name
octopus. The squid and cuttlefish also have 2 long, tentacles
with flattened paddles.
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The cuttlefish has an internal shell that is sold to pet stores as
a source of calcium for birds.
Cuttlefish Video
Cuttlefish
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The spiraled shell of the chambered
nautilus is lined with mother-of-pearl
and is perfectly proportioned
mathematically.
Gas and liquid exchange occurs through
the walls and allows the nautilus to
regulate buoyancy.
Oysters are at the center of the aquaculture
industry and are raised for culturing pearls.
If an irritant such as a grain of sand gets trapped under the
oyster’s mantle, it secretes a coating of a pearl-like material called
nacre. Selected oysters are carefully raised to produce pearls of
various sizes and colors.
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Squid Internal Anatomy
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