Phylum Mollusca
General Features
size range & diversity
vary and unique to all classes
mantle
feeding nad locomotion
feeding
locomotion
Aplacophora
less than 5cm
Polyplacophora
2-12 cm but big as 30cm
dorsoventrally flattened
Monoplacophora
3-4cm in diameter
dome-shaped
Cephalopoda
15mm-18mm
Bivalvia
1m; 1000kg
Gastropoda
1mm-50cm
spiraled
Scaphopoda
2-8cm
Tubular, tusk-shaped
Covers the visceral mass
extensions secrete mucus
secretes the shell
three layers
lacks in Aplacophora
periostracum
middle prismatic
inner nacreous layer
calcareous spines
reduced in cephalopods
multiple in polyplacophora
eight articulating plates
defense mechanism
surrounds the girdle
only present in polyplacophora
siphon - bivalves
cavity
house ctenidia
cilia on surface
lacks in gastropoda and scaphopoda
Feeding and Locomotion
feeding
locomotion
mouth in the anterior end
contains radula
biological file or scraper
absent in bivalves
captacula (sticky ends)
only present in scaphopoda
algae and organic matter
muscular foot
houses the visceral mass
contains dorsoventral and transverse muscles
works with hemocoel
forms the hydrostatic skeleton
forms funnel - cephalopods
absent in aplacophora
works with mucus
in form of retrograde waves
Forms and Functions
external features
internal features
head
foot
mantle
mantle cavity
contains tentacles
captacula in scaphopods
labial palps in bivalves
arms in cephalopods
body cavity
fluid-filled hemocoel
nervous system
tetraneural
pair of ganglia
pair of nerve cords
attached to the brain
pedal nerve cords
apical brain and suboesophageal ganglia fuse together
forms ring around esophagus
sensory structures
statocyst and osphradia
gastropoda
eyespots
image-forming eyes
cephalopods
aesthetes
polyplacophora
Digestive system
digestive glands
absent in carnivore's species of gastropods
crystalline style
intestine
anus
opens in the mantle cavity
Circulatory system
heart
three in cephalopods
absent in scaphopods
surrounded by pericardial cavity
open
except cephalopods
paired metanephridia
opens into pericardial cavity
Nephridiopores
opens into mantle cavity
Respiratory system
pigment = hemocyanin
Reproductive System
gastropoda
gas exchange through mantle
scaphopoda
gills equipped with cilia
bivalve
dioecious
monoecious
Monoplacophora
trochophore and veliger larva
gonads
unique in all classes
unpaired - scaphopoda
single - gastropoda
embedded in foot - cephalopoda
posterior end - cephalopoda
exteriorly - monoplacophora
on pericardial cavity - polyplacophora
spermatophore and hectocotylus arms in cephalopods
gonoducts in polyplacophora