bi103 lab 06 - phylum mollusca

8/3/2019 BI103 Lab 06 - Phylum Mollusca

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Phylum MolluscaPhylum Mollusca

BI103 Marine BiologyBI103 Marine Biology

Laboratory Notes 06Laboratory Notes 06


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mollismollis from Latin = softfrom Latin = soft

Molluscs are softMolluscs are soft--bodiedbodied

invertebratesinvertebrates

Molluscs exhibit extreme diversity inMolluscs exhibit extreme diversity inexternal body planexternal body plan

The Mollusca is the second largestThe Mollusca is the second largest

phylum of animals, with more thanphylum of animals, with more than110,000 species described110,000 species described


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General CharacteristicsGeneral Characteristics

1)1) Bilateral symmetryBilateral symmetry

2)2) Body mass (or visceral mass)Body mass (or visceral mass)

3)3) Protective armor (usually a dorsalProtective armor (usually a dorsal

shell)shell)4)4) Head, with sensory and feedingHead, with sensory and feeding

organsorgans

5)5) Muscular ventral foot for locomotionMuscular ventral foot for locomotion


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Specialized StructuresSpecialized Structures

Two structures are unique to theTwo structures are unique to the

MolluscaMollusca1)1) MantleMantle = extension of the visceral= extension of the visceral

massmass

Extends outward and downward to form aExtends outward and downward to form a

mantle cavity between its outermost edgemantle cavity between its outermost edge

and the visceral massand the visceral mass

2)2) RadulaRadula = Latin for= Latin for scraperscraper Can be considered aCan be considered atoothed tonguetoothed tongue


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Functions of the MantleFunctions of the Mantle

1)1) Secretes the molluscan shell,Secretes the molluscan shell,

increasing it in size and strengthincreasing it in size and strength

2)2) Houses respiratory surfaces (i.e.,Houses respiratory surfaces (i.e.,

gills orgills orlunglung))a)a) Mantle cavity is lined with cilia thatMantle cavity is lined with cilia that

pass water current over thepass water current over the

respiratory surfacesrespiratory surfacesb)b) Current also eliminates fecal matter,Current also eliminates fecal matter,

excretory products, and reproductiveexcretory products, and reproductive

materialmaterial


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3)3) Houses external openings ofHouses external openings ofdigestive, excretory, anddigestive, excretory, andreproductive systemsreproductive systems

4)4) Houses olfactory sensory organsHouses olfactory sensory organs5)5) Provides spaceProvides space

a)a) Head and foot can be retracted intoHead and foot can be retracted intomantle cavity for protectionmantle cavity for protection

b)b) Forms a brood pouch in someForms a brood pouch in somespeciesspecies

c)c) Is modified into jet propulsion organIs modified into jet propulsion organin squids and octopusesin squids and octopuses


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RadulaRadula TheThe radularadula essentiallyessentially

consists of up toconsists of up to250,000 teeth250,000 teethattached to a flexible,attached to a flexible,chitinouschitinous membrane,membrane,mounted on amounted on a

cartilaginous rodcartilaginous rod The radula isThe radula is

extended from theextended from themouth andmouth andlickedlickedororscraped across thescraped across the

surface upon whichsurface upon whichthe mollusc is feedingthe mollusc is feeding(i.e., like a rasp)(i.e., like a rasp)


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The radula may be modified forThe radula may be modified fordifferent feeding strategiesdifferent feeding strategies

DrillDrill

(e.g., moon snails and some(e.g., moon snails and some muricidsmuricids))

DartDart

(e.g.,(e.g., ConusConus, some, some turridsturrids andand terebridsterebrids))

Reduced or absentReduced or absent


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EvolutionEvolutionThe fossil record ofThe fossil record ofmolluscs ismolluscs is

long (down to the earlylong (down to the early

Cambrian),Cambrian),

extensive (about 70extensive (about 70000 fossil species have000 fossil species have

been described), andbeen described), and

highly informative.highly informative.

Because the formationBecause the formation

of the gastropod orof the gastropod orbivalvebivalve protoconchprotoconch isis

correlated with the typecorrelated with the type

of larval life (e.g.,of larval life (e.g.,

lecithotrophic versuslecithotrophic versus

planktotrophic), the fossilplanktotrophic), the fossilrecord of molluscs alsorecord of molluscs also

provides informationprovides information

about the life cycle ofabout the life cycle of

extinct species and taxaextinct species and taxa


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ClassificationClassification ClassClass

PolyplacophoraPolyplacophora a.k.a.a.k.a. chitonschitons

Shell consists of 8Shell consists of 8

platesplates


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Class AplacophoraClass Aplacophora

a.k.a.a.k.a. solenogasterssolenogasters Small, wormSmall, worm--likelike

More common inMore common in

deep water (i.e.,deep water (i.e.,600600--1,200 feet),1,200 feet),

but may be foundbut may be found

in shallowin shallow

interstitialinterstitialcommunitiescommunities


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ClassClassMonoplacophoraMonoplacophora

SegmentedSegmented

limpetslimpets Mostly occur inMostly occur in

deep waterdeep water

(6,000(6,000--21,00021,000

feet)feet)

Thought to beThought to be

extinct sinceextinct since

Silurian (400Silurian (400 MyaMya))until 1957until 1957

NeopilinaNeopilina = living= living

fossil, discoveredfossil, discovered

until 1957until 1957


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Class BivalviaClass Bivalvia a.k.a. clams,a.k.a. clams,oysters, andoysters, andmusselsmussels

Shell consists ofShell consists oftwo articulatedtwo articulatedvalves heldvalves heldtogether by atogether by a

chitinouschitinous ligamentligament Lack radula andLack radula and

head, andhead, andsometimes lacksometimes lack

the muscular footthe muscular foot Mostly suspensionMostly suspension

feeders, but alsofeeders, but alsodeposit feedersdeposit feeders

and predatorsand predators


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Class CephalopodaClass Cephalopoda

Includes squids,Includes squids,cuttlefishes,cuttlefishes,

octopuses, andoctopuses, and

nautilusesnautiluses

Most advancedMost advancedmolluscan nervousmolluscan nervous

systemsystem

All are activeAll are active

predatorspredators Shell reduced orShell reduced or

absentabsent

Foot modified intoFoot modified into

tentaclestentacles

Only about 800 extantOnly about 800 extant

species, compared tospecies, compared to

about 7,500 fossilabout 7,500 fossil

speciesspecies


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Class ScaphopodaClass Scaphopoda a.k.a. tusk shells,a.k.a. tusk shells,

although namealthough name

literally meansliterally meansshovel footshovel foot

(which actually(which actually

refers to therefers to the

head)head) Shell is open onShell is open on

both endsboth ends

Scaphopods areScaphopods areburrowers in mudburrowers in mud

and sedimentsand sediments

Lack eyesLack eyes


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Class GastropodaClass Gastropoda

Includes snailsIncludes snails

and slugsand slugs

Most specioseMost speciosegroup of molluscsgroup of molluscs

(~70% of species(~70% of species

in Mollusca)in Mollusca)

Asymmetrical,Asymmetrical,

univalvedunivalved, usually, usually

spiral shellspiral shell

Characterized byCharacterized bytorsiontorsion


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TaxonomyTaxonomy

Haliotis sp.


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Patella flexuosa


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Patelloida chamorrorum


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Trochus niloticus


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Turbo petholatus


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Modulus tectum


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Planaxis sulcatus


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Cerithium nodulosum


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Dendropoma maxima


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Strombus dentatus


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Lambis lambis


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Cypraea tigris


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Cypraea talpa


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Cypraea vitellus


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Cypraea lynx


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Cypraea carneola


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Cypraea aurantium


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Natica gualtieriana


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Tonna perdix


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Casmaria ponderosa


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Cassis cornuta


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Charonia tritonis


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Chicoreus brunneus


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Drupella rugosa


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Vasum turbinellus


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Harpa amouretta


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Nassarius papillosus


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Costellariidae


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Conus geographus


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Conus striatus


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Conus tulipa


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Conus textile


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Terebra maculata


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Hastula lanceolata


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Chromodoris n. sp.


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Halgerda tessellata


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Haminoea cymbalum


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Anadara sp.


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Hyotissa hyotis


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Lopha cristagalli


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Pinctada margaritifera


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Pinna muricata


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Spondylus violacens


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Tridacna gigas


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Tridacna derasa


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Tridacna maxima


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Tridacna squamosa


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Tridacna crocea


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Hippopus hippopus


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Hippopus hippopus (bleached)


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Periglypta sowerbyi


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Octopus cyaneus


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Octopus ornatus


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Sepia latimanus


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Sepioteuthis lessoniana

bi103 lab 06 - phylum mollusca

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