Bio 125 lecture #10 (2/24/15)
I. Phylum Mollusca
A. Class Gastropoda
1. Subclass Opistobranchia (nudibranchs)
B. Class Polyplacophora (chitons)
1. Body plan
2. Feeding
3. Reproduction
C. Class Bivaliva (clams, etc)
1. Body plan
2. Feeding
3. Lifestyle variations
4. Reproduction
D. Class Cephalopoda
1. Body Plan
2. Protection
3. Nervous system/Behavior
4. Feeding
5. Reproduction
Phylum Mollusca: Class Gastropoda
Nudibranchs (“naked gills”)
Dorids
1. Rhinophores & oral
tentacles retractable
2. Circlet of
retractable gills around
anus
3. Most feed on
sponges, some tunicates
-> steal toxins
Nudibranchs (sea slugs)
Reproduction
Hermaphrodites
(Cross fertilize)
Phylum Mollusca: Class Gastropoda
Nudibranchs (“naked gills”)
2 forms:
Dorids
Aeolids
Phylum Mollusca: Class Gastropoda
Subclass Opistobranchia
Nudibranchs (“naked gills”)
Aeolids
2. Cerata
1. Propodial
tentacles (predation
on hydroids)
3. No true gills
(use cerata)
4. Cerata contain gut
extensions
– store cnidocytes
stolen from Cnidarian
prey
Phylum Mollusca - Class Polyplacophora
(Chitons)
Body Plan
• 8 exposed plate-like shells
(1 exception- gumboot chiton)
• internal organs NOT
coiled (as in snails)
• Many paired gills in
mantle cavity
Veliger larvae
• Cilia create
respiratory currents
Detorsion at settlement
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Phylum Mollusca: Class Polyplacophora (Chitons)
Feeding:Mainly herbivores of microalgae on rocks
• Trocophore
larvae
•Radula hardened with magnetite
• Carnivorous Placiphorella velata
Phylum Mollusca: Class Bivalvia
(clams, mussels, oysters)
Derek Gerstmann, U W. Australia
Phylum Mollusca: Class Bivalvia
Lifestyle Variation
1. Burrowers
• Some clams – enlarged foot
for burrowing/digging
• mantle may be fused &
elongated into 2 siphons
Phylum Mollusca: Class Bivalvia
Lifestyle Variation
2. Boring bivalves
Phylum Mollusca: Class Bivalvia
Lifestyle Variation
3. Sessile (attached to substrate surface)
• Shipworm
• foot reduced or absent (scallops, oysters)
• attach either by 1 valve (scallops, oysters)
or byssal threads (mussels)
ipworm
urrows
th shell
phons
oject out
wood
Phylum Mollusca: Class Polyplacophora (Chitons)
Reproduction
• Separate sexes
• Broadcast spawn – external fertilization
• Date mussels
• Rock-boring piddock
http://www.npr.org/templates/story/story.php?storyId=124319594
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Phylum Mollusca: Class Bivalvia
Lifestyle Variation
4. Free-living
Phylum Mollusca:
Class Bivalvia
Reproduction
• Separate sexes
• reduced foot
• Broadcast spawn
• veliger with 2 valves
• No torsion
Phylum Mollusca
Class Cephalopoda
Cuttlefish
Basic Body form
a. Shell/Structural Support
1. Octopus: none
2. Squid: pen
“head-foot”
Octopus
Squid
Phylum Mollusca, Class Cephalopoda
Chambered Nautilus
Phylum Mollusca, Class Cephalopoda
Basic Body form
a. Shell/Structural Support
3. Cuttlefish: cuttlebone (also for buoyancy)
Phylum Mollusca, Class Cephalopoda
Basic Body form
a. Shell/Structural Support
4. Nautilus:
External shell
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Phylum Mollusca, Class Cephalopoda
Basic Body form
b. foot modified into arms & tentacles
- with suckers (except nautilus)
Phylum Mollusca, Class Cephalopoda
Basic Body form
c. distinct head, near foot
Arms – suckers
along whole length
Tentacles –
suckers only at
tips
Large, complex
eyes
Mouth surrounded by arms, tentacles
Phylum Mollusca, Class Cephalopoda
Basic Body form
d. body protected by thick, muscular
mantle
Phylum Mollusca, Class Cephalopoda
Basic Body form
e. mantle cavity behind head
Encloses 2-4 gills, NO cilia
Modified into 2
lateral fins in
squid
Phylum Mollusca, Class Cephalopoda
Basic Body form
f. mantle rolled into siphons
3 functions of
siphon:
Phylum Mollusca, Class Cephalopoda
Protection
1.Ink
2. Camouflage
1.Breathing
(self & eggs)
2. Swimming
3. Defense
Siphon
http://www.youtube.com/watch?v=PmDTtkZlMwM
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Phylum Mollusca, Class Cephalopoda
Nervous/sensory system & Behavior
1. Most complex invertebrate nervous system
2. Single, large brain
3. Giant nerve fibers
(rapid impulses)
4. High learning
capacity
5. Elaborate
disguises
http://www.youtube.com/watch?v=RUN6c5yWJhQ&feature=fvw
Bio 125 lecture #10 (2/24/15) Study Questions
1. List 2 major differences between aeolid & dorid
nudibranchs (Subclass Opistobranchia.
2. Describe how each of aeolid and dorid
nudibranchs protect themselves
3. How many shells does Class Polyplacophora
(chitons) have?
4. Class Bivalvia differs from other molluscs in
that they lack a _____ and a _________
5. How do bivalves eat? What part of their body
do they use & what features help them?
6. List the 4 different lifestyles of bivalves and
provide one adaptation for living in each
different environment.
Bio 125 lecture #10 (2/24/15) Study Questions
7. Class Cephalopoda: Describe the shell & foot
modification in each of the following: octopus,
squid, cuttlefish, nautilus.
8. List 3 possible functions of the siphon in
Cephalopods.
9. Chromatophores are specialized skin cells in
cephalopods that are used for protection.
Describe how they are structured and how they
work.
10. Besides color change, what is one other way
that most cephalopods can defend themselves?
11. Octopi have more complex behavior than
other molluscs. Explain why this is so.
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