12 Mollusca - Foot and Shell

Dr. PARVISH PANDYA’s presentation

“Foot & Shell inMollusca”

A presentation compiled from various sources by

Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.


Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at [email protected] a lot and have fun in teaching & learning Zoology….

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://faculty.pnc.edu/jcamp/parasit/parasit.html

http://www.amnh.org/rose/hope/creatinghope/

http://www.biosci.ohio-state.edu/~zoology/eeob405/

http://www.tulane.edu/~wiser/protozoology/pwpt/

http://www.iep.water.ca.gov/suisun/photos/wildlife.html

http://www.uta.edu/biology/marshall/2343/

http://www.uta.edu/biology/faculty/faculty.html

http://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htm

http://bio.fsu.edu/

http://www.aw-bc.com/

http://www.nhm.org/

http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

mailto:[email protected]


Phylum Mollusca


Phylum Mollusca


Phylum Mollusca (mollis, soft)

• Body usually an anterior head, ventral foot and a dorsal visceral mass.

• Covered by a fleshy outgrowth of the body wall called a mantle.– Shell if present is secreted by the mantle

• Radula- a tongue-like structure bearing transvers rows of minute chitinous teeth.

• Good phylum for demonstrating Adaptative Radiation.

• With the exception of Monoplacophora, the phylum is unsegmented.


Systems

•• SkeletalSkeletal- Mantle may secretes a shell. Use hydrostatic pressure for ventral muscular foot.

•• MusclesMuscles -Ventral muscular foot and other muscles present.

•• DigestiveDigestive- complete complex with salivary glands, digestive gland and Rasping tongue (Radula).

•• CirculatoryCirculatory - Open except for Cephalopoda. Dorsal heart, usually in a pericardial cavity.

•• RespiratoryRespiratory - Ctenidia (gills) in mantle cavity, respiratory pigment is copper.


Systems

•• ExcretoryExcretory- by nephridia usually connecting to the pericardial cavity, – the coelom is usually reduced to the cavities of the nephridia,

gonads and pericardium.•• NervousNervous - Nerve ring with various pairs of ganglia—two

pairs of nerve cords, one innervating the foot, the other the visceral mass (modified ventral ladder-like system)

•• IntegumentaryIntegumentary - Mantle•• EndocrineEndocrine - nervous systems produces hormones.•• ReproductiveReproductive - varied- monoecious, protandric, or

dioecious. Larva in marine = trochophore and veliger, in freshwater clam is glochidium.


Molluscs

• 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


Numbers of speciesNumbers of species

Echinodermata

Ciliophora

ChordataMollusca

PlatyhelminthesNematoda

PoriferaAnnelida

Other

ApicomplexSarcomastigophora

Arthropoda


Economics

• Pearls• Burrowing shipworms • Snails & slugs

– Garden pests– Food– Intermediate hosts for

parasites


Phylum Mollusca• Ventral Foot

– Locomotion• Mantle

– Encloses mantle cavity• Shell• Radula• Coelom• Metanephridia• Open circulatory

system– Closed in cephalopods


Trochophore Larva• Same type as Phylum

Annelida


MyxozoaMyxozoaMyxozoa

ArthropodaArthropodaArthropoda AnnelidaAnnelidaAnnelidaMolluscaMolluscaMollusca

LophophoresLophophoresLophophores

HemichordataHemichordataHemichordata

VertebrataVertebrataVertebrata

Other pseudocoelomates

Other Other pseudocoelomatespseudocoelomates

NematodaNematodaNematoda

PoriferaPoriferaPorifera

CtenophoraCtenophoraCtenophoraCnidariaCnidariaCnidaria

PlacozoaPlacozoaPlacozoa

PlatyhelminthesPlatyhelminthesPlatyhelminthesNemerteaNemerteaNemertea

CiliophoraCiliophoraCiliophoraSarcomastigophoraSarcomastigophoraSarcomastigophora

MicrosporaMicrosporaMicrosporaApicomplexaApicomplexaApicomplexa

MesozoaMesozoaMesozoa

EchinodermataEchinodermataEchinodermata

CrustaceaCrustaceaCrustaceaChelicerataChelicerataChelicerata

UniramiaUniramiaUniramia

Other ChordataOther Other ChordataChordata


Body PlanBody Plan

Mantle cavityMantle cavityMantle cavity

CtenidiumCtenidiumCtenidium

MetanephridiumMetanephridiumMetanephridium

GonadGonadGonad

Stomach and digestive glandStomach and digestive glandStomach and digestive gland FootFootFoot

Pericardial cavityPericardial cavityPericardial cavity

RadulaRadulaRadula


Dorsal mantle covers the visceral mass.

Dorsal mantle covers the visceral mass.


Secretes the shellSecretes the shell


Ctenidium (Respiration)Ctenidium (Respiration)


Complete digestive systemComplete digestive system


Paired ventral nerve cordsPaired ventral nerve cords


RadulaRadula


Radular Structure


Coelom - metanephridiaCoelom - metanephridia


Class Scaphopoda

• Tooth shells (or Tusk shells)– Shell and mantle

slender, tubular, and slightly curved. It is open at both ends

Dentalium


Class Scaphopoda

• Tooth shells• Shell opens on both

ends• Burrow into mud• No gills

– Mantle for gas exchange

• Feed on detritus and protozoa


Class ScaphododaClass Scaphododa


Class PolyplacophoraChitons

Class PolyplacophoraChitons


Class PolyplacophoraClass Polyplacophora• Eight dorsal plates• Reduced head• Radula reinforced

with iron– Scrape algae from

rocks


Class Polyplacophora

Mantle cavityMantle cavityMantle cavityMouthMouthMouth


FootFootFoot

AnusAnusAnus


Class PolyplacophoraClass Polyplacophora

Digestivegland

DigestiveDigestiveglandgland

StomachStomachStomach GonadGonadGonadPericardial cavityPericardial cavityPericardial cavity

NephridiumNephridiumNephridium

AnusAnusAnus

MouthMouthMouth


Class BivalviaClams, Oysters, Shipworms

Class BivalviaClams, Oysters, Shipworms


Class Bivalvia

• Two shells• Most are filter feeders• No head or radula• Burrow

– Sand, wood, rocks


Giant Clam & Burrowing Clam

Siphon


Locomotion with FootLocomotion with Foot


Zebra Mussel

• Environmental Pest• Ballast water of ships

from Europe in 1986• Attach be secreting

adhesive byssalthreads– Each other– Other mussels– Man made objects

• Pipes, plumbing


Zebra Mussel

• Live in high densities• Feed on

phytoplankton• Reproduce rapidly


Bivalve structuresBivalve structures


ExcurrentsiphonExcurrentExcurrentsiphonsiphon

HingeHingeHinge

FootFootFoot

Labial palpLabial Labial palppalp

IncurrentsiphonIncurrentIncurrentsiphonsiphon


Clam anatomyClam anatomy

HeartHeartHeart

GonadGonadGonadIntestineIntestineIntestine

StomachStomachStomach IncurrentIncurrentIncurrent

ExcurrentExcurrentExcurrent

IntestineIntestineIntestine

MetanephridiumMetanephridiumMetanephridiumPericardial cavityPericardial cavityPericardial cavity



GonadGonadGonad

StomachStomachStomachIncurrentIncurrentIncurrent


Digestivegland

DigestiveDigestiveglandgland




HeartHeartHeart

IncurrentIncurrentIncurrent






HeartHeartHeart

GonadGonadGonad

IncurrentIncurrentIncurrent



Clam anatomyClam anatomyMetanephridiumMetanephridiumMetanephridium


Oysters


Pearl formation

ShellShellShell

Irritant lodged between shell and mantle

Layers of nacre secreted around foreign material

Developing pearlDeveloping pearlDeveloping pearl

EpitheliumEpitheliumEpithelium


Scallops


Oyster and Scallop

Scallop shells

Oyster cluster Oyster shells


Shipworms


Teredo (shipworm)and the Rock boring worm

Teredo Teredo in wood

Rock boring clam


Class GastropodaSnails, Slugs, Conchs, Limpets

Class GastropodaSnails, Slugs, Conchs, Limpets


Class Gastropoda

• One shell (if present)• Torsion of body


Torsion in

Gastropods


Snail

• Terrestrail• Mantle cavity

functions as lung


Snail

Tentacle(Eye stalks)TentacleTentacle(Eye stalks)(Eye stalks)

TentacleTentacleTentacle

PneumostomePneumostomePneumostome

MouthMouthMouth

Genital poreGenital poreGenital pore

ShellShellShell

AnusAnusAnus

FootFootFoot


Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Internal Structure of a Generalized Gastropod


Busycon (Whelk)

Busycon (shell removed)

Busycon shells

Busycon eggs


Other Gastropods

Abalone shells

Conch

Examples of gastropoda


AbaloneAbalone

• Several holes in top of shell– Excrete waste

• Food for man


Nudibranch

• No shell• Dorsal projections

– Gills– Nematocyst discharge


Slug

• No shell• Garden pests


Limpet

• Herbivores• Cling to rocks or other surfaces


Conch

• Large shell• Marine• Many are predators


Class CephalopodaSquids, Octopuses, Nautiluses

Class CephalopodaSquids, Octopuses, Nautiluses


Class Cephalopoda

• Shell in squid and octopus absent or vestigial

• Jet propulsion• Ink sac• Food modified into

arms and tentacles• Marine• All predators


SquidSquid

DorsalDorsal

Posterior surfacePosterior surface

RightRight

LeftLeft

VentralVentral


SquidSquid

FinFinFin

ArmArmArm

Funnel (siphon)Funnel (siphon)Funnel (siphon)

EyeEyeEye

TentacleTentacleTentacle

CollarCollarCollar


SquidSquidShell (Pen)Shell (Pen)Shell (Pen)

CtenidiumCtenidiumCtenidiumFunnelFunnelFunnel

SystemicheartSystemicSystemicheartheart

Branchial heartBranchialBranchial heartheart


Squid MaleSquid Male

Hectocotylous armHectocotylousHectocotylous armarm

PenisPenisPenisTestisTestisTestis


Squid FemaleSquid Female

Ovary with eggsOvary with eggsOvary with eggs

Nidamental glandsNidamentalNidamental glandsglandsOviducal glandOviducalOviducal glandgland

Oviducal openingOviducalOviducal openingopening


Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cephalopod Eye


Octopus

• Eight arms with suckers

• Crawl or eject water from siphon

• Change skin color• Most intelligent

invertebrate


Octopus • Eight arms


Nautilus

• Up to 94 tentacles– No suckers

• Shell with many chambers– Lives in outermost


Nautilus

• (South Pacific and Indian Ocean)


Ammonoids

• Extinct• Devonian to

Cretaceous– 400 to 65 MYA

• Died out with dinosaurs


The End