Phylum Mollusca

1
Phylum Mollusca

• soft bodied many with protective shell
• more species of molluscs in ocean than any other
  phylum, over 200,000 sp.
• the mantle is a thin tissue layer covering body
  that secretes shell
• the foot allows locomotion or attachment
• most have a head with eyes
• the radula is a tooth like structure used for
  feeding
• Ancestral larvae is a trocophore some produce a
  veliger
• Open circulatory system
• gastropods, bivalves, cephalopods, and chitons

2
Larval Forms
Trocophore
Veliger
3
Class Gastropoda - snails

• stomach foot
• most have coiled, spiral, shells (dextral or
  sinistral)
• many use radula to scrape algae for food
• predatory snails radula is modified to capture
  prey spear or drill
• also include nudibranchs and sea hares
• Consist of the Subclasses Prosobranchia (aquatic,
  gilled snails), Opisthobranchia (non-shelled),
  Pulmonata (land, lung snails)

4
(No Transcript)
5
Coiling vs. tortion
6
(No Transcript)
7
(No Transcript)
8
Tulip Snail
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
Nudibranchs (of the Subclass Opisthobranchia)

• naked gills
• no shell
• often prey on cnidarian polyps and sponges
• many are noxious tasting or use nematocysts from
  cnidarians for protection

15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
Class Bivalvia

• laterally compressed
• hinged shell
• no radula, no head filter feed by siphoning
  water
• strong muscles close shell scallops
• clams burrow in mud or sand
• Mussels (byssal threads) and oysters (cement)
  attach to surfaces
• scallops live free may move by flapping valves
• largest is giant clam

19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
A pearl is produced when a grain of sand or other
particle gets between delicate mantle membrane
and shell. The sand grain is calcified and forms
a pearl
24
(No Transcript)
25
(No Transcript)
26
Class Cephalopoda

• head foot
• predatory, highly intelligent, very good vision
• shell internal or absent
• suckers on tentacles
• beak like radula
• use jet propulsion siphon and funnel
• can change color (chromatophores) and/or release
  ink
• squid, octopus, cuttlefish, nautilus

27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
A squid measuring about 60 feet (18 meters)
washed up on a Tasmanian beach over the weekend.
(CNN.COM)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
Class Polyplacophora - chitons

• Attach tightly to rocks using foot as suction cup
• Feed on algae
• Shell is made of hard plates

40
(No Transcript)