PHYLUM MOLLUSCA - Yolamrsgallegoswebsite.yolasite.com/resources/Phylum Mollusca.pdf · PHYLUM...
Transcript of PHYLUM MOLLUSCA - Yolamrsgallegoswebsite.yolasite.com/resources/Phylum Mollusca.pdf · PHYLUM...
PHYLUM MOLLUSCA
PHYLUM MOLLUSCA
gastropods, bivalves,cephelapods
3 GENERAL BODY REGIONS
1. head- with “brain” or sense organs
2. visceral mass- contains internal organs
3. foot- muscular part of body
CLASS GASTROPODA (STOMACH-FOOTED)
Soft body in CaCO3 shell secreted by mantle
Body is bilaterally symmetrical
Ventral muscular foot for locomotion
Radula- rasping tongue, ribbon of small teeth
used to feed on algae
“breathe” through gills
HI I’M GARY!
I’M SPONGE BOB’S PET SNAIL!
HEAD-FOOT REGION
The radula is a
rasping, protrusible
feeding structure
found in most
molluscs (not
bivalves).
Ribbon-like
membrane with
rows of tiny teeth.
CLASS GASTROPODA
The shell of a gastropod
is always one piece –
univalve – and may be
coiled or uncoiled.
The apex contains the
oldest and smallest
whorl.
Shells may coil to the
right or left – this is
genetically controlled.
CLASS GASTROPODA
Early gastropods had a planospiral shell where each whorl lies outside the others. Bulky
Conispiral shells have each whorl to the side of the preceding one. Unbalanced
Shell shifts over for better weight distribution.
CLASS GASTROPODA
Many snails can
withdraw into the
shell and close it
off with an
operculum.
SNAILS
LIMPETS ABALONE
CONE SNAIL
(carnivorous)
CONCH
CLASS BIVALVIA
Clams, oysters, mussels
Laterally compressed body enclosed in two
shells(valves) joined at a hinge, controlled by
strong muscles
Gills used for getting 02 and filter feed
No head or radula
CLAMS- use foot to
burrow in sediment.
Uses siphon to draw in
water for O2 and food.
Largest bivalve-
giant clam up to
3ft in length!
(Tridacna gigas) *symbiotic
zooxanthella help its
size
OYSTERS- cement
their shells to a hard
surface, sometimes to
other oysters
MUSSELS- not burrowers, secrete strong
byssal threads to attach to surfaces
SCALLOPS-
some can
swim by
ejecting water
rapidly out
siphon
GEODUCK
PEARL OYSTERS-
when there’s an
irritant or parasite in
the mantle, shiny
layers of nacre coats
it to form pearl in
some
* Most pearls we encounter are cultured
pearls
CLASS BIVALVIA
Scallops have a row of small blue eyes along
the mantle edge.
CLASS BIVALVIA
Native freshwater clams in the U.S. are jeopardized.
Of more than 300 species once present, 12 are extinct, 42 are endangered and 88 more are of concern.
Sensitive to water quality changes,
Zebra mussels are a serious exotic invader into the Great Lakes Region.
CLASS CEPHALOPODA (“HEAD-FOOTED”)
Octopuses, squids, cuttlefish
Active lifestyles, agile swimmers
Complex nervous system, eyes similar to
ours
Reduction/loss of shell
Foot is modified into tentacles/arms with
suckers
NAUTILUS
Living fossil; not much has changed in millions of
years
Shell for protection with gas trapped in chambers
for bouyancy
90 suckerless tentacles
“Jet-propulsion” of water, controlled by
flexible siphon, for quick movement
Fans out body in defense
OCTOPUSES-
8 long arms, lack
shell, bite prey
(crabs, lobsters,
shrimp) with beak-
like jaws
Distract predators
by emitting cloud of
dark fluid produced
by ink sac
SQUID- better swimmers, elongated body, two
triangular fins, 8 arms and two tentacles
w/suckers circling mouth, shell reduced to stiff
pen
Colossal squid- largest
invertebrate, hooks on
tentacles
GIANT SQUID: up to 60ft in
length, teeth on suckers.
CUTTLEFISH
calcified internal shell that helps in bouyancy
and gives its shape (cuttle bone)
Short lifespan (~3yrs)
Males have elaborate courtship display
Kaleidoscopic changes of color
CEPHALOPOD CAMOUFLAGE
Chromatophores-Red, brown, yellow pigmented
cells under skin controlled by muscles
CEPHALODPOD CAMOUFLAGE
Iridophores-Light reflecting pigment cells
under skin (cause flash-like mirror)
Photophores- responsible
for bioluminescence in squid
CEPHALOPOD CAMOUFLAGE
Octopus and cuttlefish can control muscles
to change skin texture to match surroundings
Instant changes due to long neurons
TYPES OF……
BLUE RINGED OCTOPUS- highly
toxic saliva it releases into water or
injects to captured prey
GIANT OCTOPUS- up to 30ft and
one of most intelligent. Can
navigate a maze and remember
long term.
TYPES OF……
DUMBO OCTOPUS- lives in the deep, not
much known other than unusual earlike
flaps extending from mantle