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Todays 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: "Todays Objectives: TSW list key characteristics of mollusks, including, but not limited to, –Major organs/organ systems –Major classes and representatives."— Presentation transcript:

1 Todays 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 females 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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