Over 50000 species Coelomate Protostomes Bilaterally symmetrical Mostly marine although some live in fresh water or land Generally softbodied with a hard shell However squid amp octopi have internalized reduced or lost their shells ID: 581522
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Slide1
Phylum Molluska
Over 50,000 species
Coelomate
,
Protostomes
, Bilaterally symmetrical
Mostly marine, although some live in fresh water or land.
Generally soft-bodied with a hard shell
However, squid & octopi have internalized, reduced or lost their shells.
Body Plan
Although phenotypically diverse, mollusks share 3 common features
A muscular foot
- usually for movement
A visceral mass
- including internal organs
A
mantle
- envelopes visceral mass and secretes a shellSlide2
Molusk General AnatomySlide3
Class Polyplacophora (chitons)
Marine animals - shells divided into 8 plates
Move using a muscular foot and graze using a scraping mouthpart called a
radulaSlide4
Chiton AnatomySlide5
ChitonsSlide6
Class Bivalvia
Include clams, oysters and mussels
Have shells divided into 2 halves, connected by strong muscles
Has hatchet shaped foot for digging and anchoring
Are typically filter feeders drawing in water end expelling it through a siphon tube
Generally sessile, however, some species can quickly move by rapidly closing it's shellSlide7
Bivalve AnatomySlide8
BivalvesSlide9
Class Gastropoda
Include snails, abalone, and slugs
Largest class of mollusks ~40,000 species
Exhibit embryonic process of
torsion
Visceral mass twists 180
0
during development
Most species are herbivores, but some have modified
radullas
for boring into other mollusks
Some species have successfully colonized land Slide10
GastropodsSlide11
Giant African Land SnailSlide12
Class Cephalopoda
Unlike other mollusks, these are quick predators
Have beak-like jaws and poison to catch & immobilize prey
Beak is located @ the center of several long tentacles
Foot has been modified to form a
siphon
which allows most species to move quickly using a jet of water.
Only mollusks with a
closed circulatory system
(blood is always contained in vessels)
Very highly developed nervous system
Can learn complex behaviors
Octopi have learned to open jars to retrieve prey
May have rudimentary communication
Cuttlefish and octopi may communicate by skin coloration Slide13
Cephalopod AnatomySlide14
OctopusSlide15
SquidSlide16
CuttlefishSlide17
Cambered Nautilus