Download Mollusks - Crestwood Local Schools

• Phylum Mollusca
• Soft-bodied animals
• Internal or external shell
• Include snails, slugs, clams,
squids and octopi
• Trochophore: free-swimming
larval stage of an aquatic
mollusk
• True coeloms
• Have complex organ
systems
• Foot: muscular
part of a mollusk
• Mantle: thin layer
of tissue that
covers most of a
mollusk’s body
• Shell: structure in
mollusks made by
glands in the
mantle that secrete
calcium carbonate
• Visceral mass: area
beneath the mantle
of a mollusk that
contains the
internal organs
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Herbivorous
Carnivores
Filter feeders
Detritivores
Parasites
• Radula: flexible, tongue-shaped structure used to
capture food by snails and slugs
• Siphon: tube-like structure through which water
enters and leaves the body, capturing plankton in
the process
• Gills inside their mantle cavity
• Land snails respire using a mantle
cavity lined with blood vessels
• Typically live in moist places to keep
this lining wet
• Open circulatory system: blood is pumped
through vessels by a simple heart
– Works well for slow-moving mollusks such as
snails and clams (demands for oxygen are low)
• Closed circulatory system: can transport
blood through an animal’s body much more
quickly
• Cells of the body release nitrogencontaining waste into the blood in the
form of ammonia
• Nephridia remove ammonia from the
blood and release it out of the body
• Complexity of the nervous system
varies greatly between mollusks
• Clams and other two-shelled mollusk
lead inactive lives simple nervous
system
• Octopi and their relatives
are active and intelligent
predators  most highly
developed nervous system
of all invertebrates
• Capable of complex
behavior, such as opening
a jar to get food inside
• Move in many different
speeds
• Snails secrete mucus and
move slowly over the
surface using a rippling
motion of the foot
• Octopus uses a form of jet
propulsion, drawing water
into its mantle and forcing
it out the siphon
• Reproduce in many different
ways
• Snails and two-shelled
mollusk reproduce sexually
by external fertilization
• Some mollusk are
hermaphrodites
• Gastropods
– Shell-less or single-shelled mollusks that move by
using a muscular foot located on the ventral side
• Gastropods
– Shell-less or single-shelled mollusks that move by
using a muscular foot located on the ventral side
• Bivalves
– Have two shells that are held together by one or
two powerful muscles
• Gastropods
– Shell-less or single-shelled mollusks that move by
using a muscular foot located on the ventral side
• Bivalves
– Have two shells that are held together by one or
two powerful muscles
• Cephalopods
– Soft-bodied mollusks in which the head is
attached to a single foot; the foot is divided into
tentacles or arms
• Feed on plants, prey on animals, and
clean up their environment by filtering
algae out of the water or by eating
detritus
• Filter-feeding bivalves can be used to
monitor water quality
• Serve as subjects of biological
research
Mollusks
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Some oysters
may release over
one million eggs
in a season. Only
about one of these
eggs will survive
to become an
adult oyster.
Coelomates; bilateral symmetry, cephalized
Soft body called mantle, which secretes
material that often becomes shell
Three major classes:
Mollusks can be found
from the deepest ocean
 Gastropods (i.e. snails & slugs)
floor to the intertidal
 Bivalves (i.e. clams & oysters)
zone, in freshwater, &
 Cephalopods (i.e. squid, octopus,
everywhere on land.
cuttlefish, nautiluses)
There are over 128,000
species of living mollusks.
Most cephalopods can release
ink to distract enemies while
they swim away.
Each tentacle on a
The Giant
octopus has 240 suction
Pacific Octopus
cups to grasp its prey.
can grow up to
30 feet.
Many land
snails can
lift 10
times their
own weight
up a
vertical
surface.