Mollusks Odyssey Expeditions. 2 Phylum Molluska Means “soft body” Includes clams, snails, sea...
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Transcript of Mollusks Odyssey Expeditions. 2 Phylum Molluska Means “soft body” Includes clams, snails, sea...
MollusksMollusks
Odyssey ExpeditionsOdyssey Expeditions
2
Phylum MolluskaPhylum Molluska
• Means “soft body”• Includes clams, snails, sea slugs, and octopus• Freshwater, marine and terrestrial• Most have external shell of calcium carbonate
Jason Buchheim
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General CharacteristicsGeneral Characteristics• Posses a mantle
– Circulates water through organism– Feeding, propulsion, and/or shell
production– Gills or lungs found in mantle
cavity
• Posses a muscular foot– Used to crawl with– Tentacles in cephalopods
• Posses a radula– Tongue bearing teeth used for
feeding (like a conveyor belt)
Radula
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ClassesClasses
• Class Monoplacophora
• Class Polyplacophora
• Class Aplacophora
• Class Gastropoda
• Class Bivalvia
• Class Scaphopoda
• Class Cephalopoda
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Class MonoplacophoraClass Monoplacophora
• Relic class• Many fossilized mollusks
belong to this class • Less than 20 extant
(living) species• Single cap-like shell• Creeping foot• Found in deep water
(2000 to 7000m)
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Class PolyplacophoraClass Polyplacophora
• Chitons• Oval in shape• Eight over lapping plates• Creeping foot that
adheres tightly to rocky surfaces
• Mostly inhabit rocky intertidal zones
• Feed on algae and other organisms on the rocks
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Class AplacophoraClass Aplacophora
• Worm-like• Small (<5mm)• No shell, have
calcareous spicules in mantle
• Inhabit deep water (200 to 7000m)
• Creep or burrow• Very little known
Ventral View
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Class GastropodaClass Gastropoda• Largest class of mollusks
(30,000 species)• Snails and snail-like
organisms• Well developed head
with tentacles and eyes• Most possess single
coiled asymmetrical shell• Most crawl with foot but
some swim with it
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Gastropod SubclassesGastropod Subclasses
• Subclass Prosobranchia
• Subclass Opisthobranchia
• Subclass Pulmonata
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Subclass ProsobranchiaSubclass Prosobranchia• Mantle cavity anterior • Marine• Shelled• Many have operculum
(hard disc attached to the foot that covers the opening to the shell for protection)
• Some use mantle as camouflage
• Includes conchs, whelks, cones, abalone, and drills
• Herbivores and carnivores
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Subclass OpisthobranchiaSubclass Opisthobranchia
• Mostly marine• Shell reduced or lacking• Mantle cavity on right side, posterior,
or even lacking• Some respire through skin or external
gills• Mantle generally colorful and ornate• May have modified foot to swim with• Typically few inches in length • Includes sea hares, nudibranchs, sea
slugs• Herbivores and carnivores (have very
specific diets)
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Subclass Pulmonata
• Typically terrestrial• Shelled (except
slugs)• Mantle cavity
modified into lungs• Includes terrestrial
snails, freshwater snails and slugs
• Typically herbivores
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Class BivalviaClass Bivalvia• Consists of two hinged shells or valves• Gills used for filter feeding as well as
respiration (water brought in and out by siphons while buried in sediment)
• The mantle of some contains tentacles and eye spots to detect movement.
• No head• Second largest molluscan class (8,000
extant species)• Freshwater and marine• Includes cockles, mussels, oysters,
scallops, and clams
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Class ScaphopodaClass Scaphopoda• Tusk or tooth shell (looks like
elephant’s trunk)• Marine• Single elongated tube-like
shell.• Burrowing• Modified foot for digging • Possess tentacles to capture
interstitial (organisms found among sediment grains)
• 2-6 cm long
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Class CephalopodaClass Cephalopoda• Elongated• Highly cephalized• Well developed nervous
system• Foot modified into
specialized arms and tentacles for prey capture
• Shell external, internal, or absent
• Includes nautilus, squid, octopus, and cuttlefish
• Propulsion created by expulsion of water from mantle cavity
NOAA
Jason Buchheim
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Cephalopod SubclassesCephalopod Subclasses
• Subclass Nautiloidea
• Subclass Ammonidea
• Subclass Coleoidea
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Subclass NautiloideaSubclass Nautiloidea• Nautilus• Only 4 extant species
(most are extinct)• Multi-chambered
external shell• Gas in chambers
provides buoyancy (connected by central siphuncle canal and separated by septa)
• Siphuncle used to add or remove gas to chambers
• Many arms (~90) for prey capture
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Subclass AmmonideaSubclass Ammonidea
• All members extinct
• Coiled, external, multi-chambered shells
• Complex septa with siphuncle found along outer axis of shell
• Index fossils
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Subclass ColeoideaSubclass Coleoidea• Squid, octopus,
cuttlefish• Internal or lacking shell• Eight arms with
suckers• Squid and cuttlefish
also have two tentacles for prey capture
• Ability to camouflage is exceptional
• Have large nerve cells used in research
NOAA
Jason Buchheim
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ResourcesResources
• Barnes, Robert D. and Edward Ruppert. Invertebrate Zoology: Sixth Edition. Fort Worth: Saunders College Publishing, 1994
• Humann, Paul and Ned Deloach. Reef Creature Identification: Florida Caribbean Bahamas. Florida: New World Publications, Inc., 2003
• Kinsella, John, Drew Richardson and Bob Wohlers. Life on an Ocean Planet. California: Current Publishing Corp., 2006
• Taylor, Walter K. and Robert L. Wallace. Invertebrate Zoology: A Laboratory Manual Sixth Edition. New Jersey: Prentice Hall, 2002