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 parvishpandya@yahoo.comThanks a lot and have fun in teaching & learning Zoology….

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

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.

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

with iron– Scrape algae from

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 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 Gastropoda

• One shell (if present)• Torsion of body

Torsion in

Gastropods

• Terrestrail• Mantle cavity

functions as lung

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

TentacleTentacleTentacle

PneumostomePneumostomePneumostome

MouthMouthMouth

Genital poreGenital poreGenital pore

ShellShellShell

AnusAnusAnus

FootFootFoot

Internal Structure of a Generalized Gastropod

Busycon (Whelk)

Busycon (shell removed)

Busycon shells

Busycon eggs

Other Gastropods

Abalone shells

Examples of gastropoda

AbaloneAbalone

• Several holes in top of shell– Excrete waste

• Food for man

Nudibranch

• No shell• Dorsal projections

– Gills– Nematocyst discharge

• No shell• Garden pests

Limpet

• Herbivores• Cling to rocks or other surfaces

• Large shell• Marine• Many are predators

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

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

12 Mollusca - Foot and Shell

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