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Today’s Objectives: TSW list key characteristics of mollusks, including, but not limited to, Major organs/organ systems Major classes and representatives.

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Presentation on theme: "Today’s Objectives: TSW list key characteristics of mollusks, including, but not limited to, Major organs/organ systems Major classes and representatives."— Presentation transcript:

1 Today’s Objectives: TSW list key characteristics of mollusks, including, but not limited to, Major organs/organ systems Major classes and representatives Economic importance Evolutionary history Other major characteristics

2 Mollusks

3 New evolutionary steps
Protostomes, characters including Trochophore larvae Spiral cleavage Schizocoelous coelom formation Eucoelomate Advanced brain (some classes)

4 Key characteristics Head-foot Visceral mass Mantle & mantle cavity
True coelom only in cavities around Heart Nephridia Gonads True circulatory system Radula often present

5 Gastropoda – Gut Foots Includes snails, limpets, & slugs
Freshwater, marine, and terrestrial Display torsion Shell coiling Move on mucus with cilia or use foot

6 Gastropod Feeding Methods
Use radula to scrape algae Some radula modified to pierce prey Protostyle in digestive cavity

7 Gastropod Respiration & Circulation
Gas exchange in mantle cavity Can have 1 or 2 gills Some have a siphon Open circulatory system Blood acts as a hydraulic skeleton

8 Gastropod Nervous System
Nerves concentrated into large ganglia Most ganglia in head Simple or complex eyes Statocysts Chemoreceptors

9 Gastropod Excretory System
Nephridium (nephridia – plural) Ammonia is the primary waste product in aquatic species Uric acid is the waste for terrestrial species

10 Gastropod Reproduction
Can be monecious or dioecious Usually cross-fertilize inside the mantle cavity First development of a penis Marine gastropods produce a veliger larva

11 Economic Importance of Gastropods
Garden pests Good eating – escargot Major intermediate host for several nasty parasitic infections

12 Representative Gastropods
Nudibranchs – sea slugs Helix pomatia – escargot Garden slugs


14 Bivalvia – 2 Shells Umbo Hinge Nacre – mother of pearl
Shell made of calcium carbonate

15 Bivalve Respiration & Circulation
Gills expanded into multi-layered sheets (lamellae) Usually 2 siphons – incurrent & excurrent Open circulatory system

16 Gastropod Feeding & Digestion
Labial palps filter food particles Mucus food string Crystalline style Gastric shield

17 Bivalve Nervous System
Ganglia located in esophagus, foot, and adductor muscle Most sense organs located in margin of mantle (some have eyes there too) Statocysts Chemoreceptors

18 Bivalve Reproduction Most are dioecious, some monoecious
Gonads in visceral mass Fertilization usually external

19 Bivalve Development Trochophore larva Veliger larva
Glochidium – often parasitic

20 Bivalve Economic Importance
Often used as food Pearl production Invasive species – zebra mussel

21 Representative Bivalves
Mytilus – common mussel Pinctada – pearl oysters Dreissena polymorpha – zebra mussel


23 Cephalopoda – Head Foots
Octopi, squid, nautili, cuttlefish Tentacles Jet Propulsion Closed Circulatory System

24 Cephalopoda Shell External on nautili Internal in squid (pen)
Internal in cuttlefish (cuttlebone) Absent in octopi

25 Cephalopoda Locomotion
Use siphon for jet propulsion Squeeze mantle cavity forcefully Sometimes have external “wings” or fins for steering or slow locomotion Nautili use internal air for neutral buoyancy

26 Cephalopoda Feeding Most capture prey by sight
Use arms or tentacles to grab (sometimes have hooks and suckers) Bring prey to beaked mouth Muscular digestive system Digestion in stomach and cecum Anus near the funnel

27 Cephalopoda Respiration & Circulatory Systems
Closed ciculatory system – more efficient 3 hearts High metabolic rates Respiration through gills

28 Cephalopoda Nervous System
Complex brains Very advanced, large eyes Statocysts Touch receptors Chemoreceptors Chromatophores – color changing, signalling Some bioluminescent Ink gland

29 Cephalopoda Reproduction & Development
All are dioecious Males have testes and package sperm in spermatophores Fertilization mostly internal in back of female’s mantle cavity Octopi have external fertilization of eggs Often males have hectocotylus All larval development inside eggs.

30 Economic Importance of Cephalopods
Research on nervous system Bait Food – calamari Minerals for pets – cuttlebone

31 Representative Cephalopods
Loligo – common squid Architeuthis dux – giant squid Octopus dofleini – Giant pacific octopus


33 The Vampire Squid from Hell!!!!

34 Polyplacophora – Many Plate Bearing Animals
Used for food – hard to chew Chitons Crawl over floor using muscular foot Can roll into a ball for protection Most feed on algae Ladderlike nervous system

35 Chiton

36 Scaphopoda – Boat feet Often called “tusk shells” Burrowing animals
Conical shell open at both ends Often feed on foraminiferans Dioecious

37 Monoplacophora – One Plate Bearing Animals
Dioecious Considered living fossils Neopilina Live in deep ocean

38 Caudofoveata – Animals with Tails in Small Pits
Wormlike Deep sea floor dwellers Spicules on body wall

39 Aplacophora – No Plate Bearers
Also called solenogasters Lack a shell Nervous system similar to flatworms Live on corals Carnivores

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