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1 Unit 6.1 Phylum Mollusca
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2 Mollusks 50,000 -100,000 living species 35,000 extinct species Largest = 1000 pounds 80% less than 5 cm Soft body Most have a shell Most marine Snails terrestrial –Most habitat
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Phylum Mollusca Ventral Foot –Locomotion Mantle –Encloses body cavity Shell – created by mantle Coelom (eucoelomate) Visceral mass contains contains organs of digestion, circulation, excretion, & reproduction 3
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Phylum Mollusca Radula – rows of posteriorly oriented teeth. Basically a tongue with teeth Open circulatory system –Closed in cephalopods Mantle cavity – opens to the outside and functions in gas exchange 4
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5 Economically Important Pearls Burrowing shipworms Snails & slugs –Garden pests –Food –Intermediate hosts for parasites
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6 Trochophore Larva Same type as Phylum Annelida Shows phylogenetic relationship to higher taxa
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7 MyxozoaMyxozoa ArthropodaArthropoda AnnelidaAnnelida MolluscaMollusca LophophoresLophophores HemichordataHemichordata VertebrataVertebrata OtherpseudocoelomatesOtherpseudocoelomates NematodaNematoda PoriferaPorifera CtenophoraCtenophora CnidariaCnidaria PlacozoaPlacozoa PlatyhelminthesPlatyhelminthes NemerteaNemertea CiliophoraCiliophora SarcomastigophoraSarcomastigophora MicrosporaMicrospora ApicomplexaApicomplexa MesozoaMesozoa EchinodermataEchinodermata CrustaceaCrustacea ChelicerataChelicerata UniramiaUniramia Other Chordata
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8 Generalized Mollusk
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9 Body Plan Mantle cavity CtenidiumCtenidium Pericardial cavity MetanephridiumMetanephridium RadulaRadula GonadGonad Stomach and digestive gland FootFoot
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10 Dorsal mantle covers the visceral mass.
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11 Secretes the shell
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12 Ctenidium (Respiration)
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13 Complete digestive system
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14 Paired ventral nerve cords
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15 Radula
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16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Source: From A Life of Invertebrates, Copyright © 1979 W. D. Russell-Hunter. Radular Structure
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17 Coelom - metanephridia
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18 Class Polyplacophora Chitons
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19 Class Polyplacophora Eight dorsal plates Fishy flavor & tough to chew Reduced head Radula reinforced with iron –Scrape algae from rocks
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20 Class Polyplacophora Mantle cavity MouthMouth CtenidiumCtenidium FootFoot AnusAnus
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21 Class Polyplacophora MouthMouth DigestiveglandDigestivegland StomachStomachGonadGonad Pericardial cavity NephridiumNephridium AnusAnus
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22 Class Bivalvia Clams, Oysters, Mussels, & Scallops
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23 Class Bivalvia Two shells actually form as a single structure Most are filter feeders – helpful in removing bacteria from polluted waters No head or radula Burrowing animals –Sand, wood, rocks
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26 Giant Clam & Burrowing Clam Muscular Foot
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27 Zebra Mussel Environmental Pest Ballast water of ships from Europe in 1986 Attach by secreting adhesive byssal threads –Each other –Other mussels –Man made objects Pipes, plumbing
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28 Zebra Mussel Live in high densities Feed on phytoplankton Reproduce rapidly Attach to native mussels Killed all native mussels in Lake Erie
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29 Distribution of Zebra Mussel
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30 Bivalve structures IncurrentsiphonIncurrentsiphon CtenidiumCtenidium ExcurrentsiphonExcurrentsiphon HingeHinge FootFoot Labial palp
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31 Clam anatomy Pericardial cavity HeartHeart GonadGonadIntestineIntestine StomachStomach IncurrentIncurrent ExcurrentExcurrent IntestineIntestine MetanephridiumMetanephridium
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32 Clam anatomy GonadGonadIntestineIntestine StomachStomach IncurrentIncurrent ExcurrentExcurrent DigestiveglandDigestivegland
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33 Clam anatomy Pericardial cavity HeartHeart IncurrentIncurrent ExcurrentExcurrent IntestineIntestine
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34 Clam anatomy Pericardial cavity HeartHeart GonadGonad IncurrentIncurrent ExcurrentExcurrent IntestineIntestine MetanephridiumMetanephridium
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Oysters 35 Able to form pearls – the color depends on prevalent minerals in water Only eat oysters during cold months – less bacteria in filtrate Can cause severe wounds and Vibrio infections Use extreme caution when exiting boats in oyster infested waters
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Vibrio vulnificus 36
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37 Pearl formation Developing pearl EpitheliumEpithelium ShellShell An irritant, usually sand, becomes lodged between the shell and mantle. Layers of shell are then secreted by the mantle around the foreign material. The mineral content of the water determines the color of the resulting pearl.
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38 Scallops Good swimmers – the only migratory bivalve Movement achieved by rapidly opening and closing shell Mostly free-living Highly regular and geometrically symmetrical shells
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39 Shipworms Highly reduced shells. Known as termites of the sea. Burrow into any submerged wooden structure including ships, docks, & piers. Special gland called Deshayes gland contains bacteria that allow shipworms to digest cellulose
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Shipworms 40
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41 Class Gastropoda Snails, Slugs, Conchs, Abalones, & Limpets
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42 Class Gastropoda One shell (if present) Torsion of body – allows head to retract before tail, allows clean water to enter mantle cavity, and orients sensory organs in direction of forward movement. Largest & most varied molluscan class
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Torsion 43
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Snails Terrestrial is most encountered type but marine varieties are much more numerous. Mantle cavity functions as lung in terrestrial snails. Herbivores, omnivores, and carnivores. All land snails are hermaphrodites. 44
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45 Snails Tentacle (Eye stalks) TentacleTentacle PneumostomePneumostome AnusAnus FootFoot MouthMouth Genital pore ShellShell
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46 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Internal Structure of a Generalized Gastropod
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Nudibranchs No shell – commonly called sea slugs Dorsal projections aid in respiration and protection – they eat hydroid cnidarians, conserve the nematocysts, and move them to the dorsal projections 47
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Nudibranchs Some of the most colorful creatures on earth. Unlike most other gastropods, they are bilaterally symmetrical. One species of nudibranch is the only animal that can photosynthesize. However, it must also eat to satisfy all of its energy needs. 48
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Nudibranchs 49
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Abalones Several holes in top of shell –Excrete waste –Used for respiration Shell is incredibly strong. It is made of microscopic calcium carbonate tiles stacked like bricks. Live primarily on cooler waters. 50
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Abalones Source of food and decoration – the inner part of the shell is highly iridescent and used for mother-of- pearl inlays. Cling to rocks in subtidal zone and feed on primarily red algae. 51
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52 Slugs No shell Garden pests Bodies are prone to desiccation – confined to moist environments Secrete mucous to help prevent desiccation and to protect themselves against predation.
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Limpets 53 Gastropods with conical shaped shells Attach to rocks or other hard substrates in intertidal zones. Contain gills and lungs to survive in intertidal zone. May be eaten in certain parts of the world.
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54 Conchs Large shell with highly spiraled character All species are marine Conchs are found in the Indian & Pacific oceans as well as in the Caribbean sea. Their meat is used as food and their shells are highly prized as decorations.
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55 Class Cephalopoda Squids, Octopi, Nautiluses
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Class Cephalopoda Shell in squid and octopus absent or vestigial. Present in nautilus. Movement via jet propulsion Ink sac used for defense Foot modified into arms and tentacles All marine and predatory. 56
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57 Squid Dorsal Ventral Posterior surface Right Left
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Squid Have 8 arms and two tentacles. Siphon allows jet propulsion in both directions along the axis of the animal. Swimming fins located on either side of the mantle. Giant axon is the largest neuron in the animal kingdom 58
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59 Squid FinFin ArmArm Funnel (siphon) EyeEye TentacleTentacle CollarCollar
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60 Squid Shell (Pen) CtenidiumCtenidium FunnelFunnel SystemicheartSystemicheart Branchial heart
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61 Squid Male TestisTestis Hectocotylous arm PenisPenis
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62 Squid Female Ovary with eggs Nidamental glands Oviducal gland Oviducal opening
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63 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cephalopod Eye
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Octopus Eight arms with suckers Crawl or eject water from siphon Change skin color –chromatophores Most intelligent invertebrate 64
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Chromatophores 65
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66 Nautilus Up to 94 tentacles –No suckers Shell with many chambers – lives in outermost chamber. Considered to be a living fossil. Can alter the amount of gasses in shell chambers thus controlling its position in the water column.
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Nautilus 67
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68 Class Scaphopoda Tooth shells Shell opens on both ends Burrow into mud No gills –Mantle for gas exchange Feed on detritus and protozoa
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69 Class Scaphopoda
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70 The End
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