Phylum Mollusca

3cuttlefish Nautilus Giant squid Architeuthis

clam

chiton

snail

slug

octopus

scallop

CHARACTERISTICSCHARACTERISTICS Second largest phylum in the animal kingdom (80000 living species and 40000 fossil species) Soft bodied animalsBody: head, foot and visceral hump Microscopic to macroscopicThey include chitons, snails, slugs, clams, oysters, cuttlefish, squids, octopods, scaphopods, ……. Slow to active organisms Coelomate, triploplastic, unsegmented

Second largest phylum in the animal kingdom (80000 living species and 40000 fossil species) Soft bodied animalsBody: head, foot and visceral hump Microscopic to macroscopicThey include chitons, snails, slugs, clams, oysters, cuttlefish, squids, octopods, scaphopods, ……. Slow to active organisms Coelomate, triploplastic, unsegmented

Terrestrial, freshwater, or marine environments Occur in a wide variety of environments Have different modes of nutrition Bilateral symmetry, torsion and coiling in

gastropods True coelom is reduced Skin is soft and often secrets the exoskeleton

or the shell Respiration by one to many gills (ctenidia) Radula in most molluscs Circulatory system of open type (except

cephalopods)

Blood contains haemocyanin and amoebocytes The nervous system is composed of a nerve

ring around the oesophagus and two pairs of nerve cords Sense organs include tentacles, eye spots,

statocysts in foot and osphradia beside gillsExcretion by a pair of u- shaped metanephridia Molluscs are unisexual (dioecious) but some

are hermaphrodite (monoecious) Fertilization is mostly external and rarely

internal Development is direct (no larva) or indirect

through free swimming trochophore and/or veliger larvae

Economic importance of Mollusca

Human food

Pearls

Buttons

Decoration

Ship-worms

Intermediate hosts of some parasites

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Scallops coarsely ribbed food

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Destructive Burrow into wood

Shipworms

The soft edible parts of themolluscs represent an important

source of animal protein

The shells are used to manufacture beautiful gifts or to decorate the

furniture

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Characteristics of Phylum Mollusca

All organ systems are present, well-developed– Respiratory organs– Circulatory system, with heart

Greater body size possible

Freshwater clamSquid

GENERAL BODY PLANGENERAL BODY PLAN Head

Ventrally located muscular foot

Dorsally located visceral mass

Mantle / pallium – for shell/spicule secretion

Radula (except for bivalves)

Complete digestive tract

Gonads in visceral mass

Monoecious or dioecious

Head

Ventrally located muscular foot

Dorsally located visceral mass

Mantle / pallium – for shell/spicule secretion

Radula (except for bivalves)

Complete digestive tract

Gonads in visceral mass

Monoecious or dioecious

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Molluscan body form

2-part body plan:1. Head-foot2. Visceral mass

Octopus

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Mollusk Body Plan

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Head-footFoot:

ventral Muscular structure Locomotion Attachment modifications

Octopushttp://acolyte.org/images/octopus.png

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Head-foot

Snail radula

Head:– anterior– Cephalic sensory

organs– Feeding organs:

Radula– Most molluscs (not

bivalves)– rasping structure– Tongue-like– Rows backward-

pointing “teeth”– Scraping food– drilling

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Visceral mass Digestive organs Reproductive

organs Circulatory

organs Respiratory

organs

Mantle Attached to

visceral mass Dorsal skin folds protective In some, mantle

secretes protective shell over visceral mass

Chiton

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Mantle cavity– Space between

mantle and foot– Opens to outside– Functions:

Gas exchange (respiration)

Excretion/elimination

Release reproductive products

Subphylum Conchifera: with 1 shell; (-) spicules

1. Class Gastropoda2. Class Bivalvia3. Class Cephalopoda4. Class Scaphopoda5. Class Monoplacophora

Subphylum Aculifera: with multiple shell plates; (+) spicules1. Class Polyplacophora2. Class Aplacophora

Subphylum Conchifera: with 1 shell; (-) spicules

1. Class Gastropoda2. Class Bivalvia3. Class Cephalopoda4. Class Scaphopoda5. Class Monoplacophora

Subphylum Aculifera: with multiple shell plates; (+) spicules1. Class Polyplacophora2. Class Aplacophora

CLASSIFICATIONCLASSIFICATION

Class MonoplacophoraClass Monoplacophora

Bilaterally symmetricalHave a dorsal, single, dome- or

cap-shaped shellHas a broad, flattened footIncludes many fossil species

Bilaterally symmetricalHave a dorsal, single, dome- or

cap-shaped shellHas a broad, flattened footIncludes many fossil species

Neopilina Subphylum Conchifera;Class Monoplacophora

Neopilina Subphylum Conchifera;Class Monoplacophora

N. galatheae

Class AplacophoraClass Aplacophora

Worm-like molluscs called SOLENOGASTERS

With oblong, cylindrical to vermiform bodies

No shellLack a well-defined headRadula and jaws sometimes present

Worm-like molluscs called SOLENOGASTERS

With oblong, cylindrical to vermiform bodies

No shellLack a well-defined headRadula and jaws sometimes present

Neomenia Subphylum Aculifera;

Class Aplacophora

Neomenia Subphylum Aculifera;

Class Aplacophora

N. yamamotoi

Chaetoderma Subphylum Aculifera;

Class Aplacophora

Chaetoderma Subphylum Aculifera;

Class AplacophoraC. japonicum

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Classes of Mollusc

Chiton

Class Polyplacophora“many plate-

bearers”ChitonsDorsoventrally

flattenedShell= 8

overlapping dorsal plates

marineUnderside of

chiton

Class PolyplacophoraClass PolyplacophoraInclude marine chitons

Bodies elongated and dorsoventrally flattened

Shell divided into:–7 or 8 overlapping plates–Flat, creeping foot

Head reduced

No eyes

Well defined mouth with radula

Include marine chitons

Bodies elongated and dorsoventrally flattened

Shell divided into:–7 or 8 overlapping plates–Flat, creeping foot

Head reduced

No eyes

Well defined mouth with radula

Chiton Subphylum Aculifera;Class Polyplacophora

Chiton Subphylum Aculifera;Class Polyplacophora

C. glaucus

8 calcareous plates

girdle

Muscular foot

Acanthozostera Subphylum Aculifera;Class Polyplacophora

Acanthozostera Subphylum Aculifera;Class Polyplacophora

A. gemmata

Class GastropodaClass Gastropoda Members usually

sluggish and sedentary Mostly with

asymmetrical bodies Most with single,

conical and spiral shellMay be reduced or

absent (e.g. nudibranch) (+) Cephalic tentacles Simple eyes Radula Jaws Large, prominent foot

Members usually sluggish and sedentary Mostly with

asymmetrical bodies Most with single,

conical and spiral shellMay be reduced or

absent (e.g. nudibranch) (+) Cephalic tentacles Simple eyes Radula Jaws Large, prominent foot

eyespots

tentacles

jaws

RADULARADULA

toothed chitinous ribbon in the mouth of most molluscs used for cutting

and chewing food before it enters the esophagus It is present in all

molluscs except bivalves

toothed chitinous ribbon in the mouth of most molluscs used for cutting

and chewing food before it enters the esophagus It is present in all

molluscs except bivalves

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Class Gastropoda Well-developed sense organs

– Eyes at base or at end of tentacles

Major Changes from Generalized Mollusc

Development of head Dorsoventral elongation Shell – from shield to retreat Torsion Conispiral coiling and asymmetry

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Class Gastropoda

May have protective shell

TorsionWeight of shell over head, mantle

cavity posteriorTorsion – 180o counterclockwise

rotation of visceral mass, shell, mantle, mantle cavity

Occurs in larvae not adultFirst gastropodsDetorsion

Costs of Conispiral Shell

Loss of a gill, nephridium, atriumMantle cavity (anus and

nephridiopore) now anterior and near mouth

Compensation - changes in water flow or shell structure

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Coiling–Absent in some–Visceral mass/mantle may be

coiled–Successive coils- whorls–Caused pressure on right side

adaptation: loss of rt. kidney, auricle, gill Water enters via left, leaves right

LocomotionMost move using footMost have ciliated sole and

secretory glands (mucus producing)

Hard-bottom dwelling and terrestrial, and large soft-bottom snails - undulating wave of muscle contractions

FeedingMost often thought of as algal scrapers (radula)

Deposit feedersSuspension feedersScavengersPredatorsParasites

Turbo (turban snail) Subphylum Conchifera;

Class Gastropoda

Turbo (turban snail) Subphylum Conchifera;

Class Gastropoda

• Torsion• Whorl• Spire

• Torsion• Whorl• Spire

Cypraea (cowries) Subphylum Conchifera;

Class Gastropoda

Cypraea (cowries) Subphylum Conchifera;

Class Gastropoda

Shell uncoiled

Nudibranchsoft-bodied snailsNudibranchsoft-bodied snails

Spanish shawl

Spanish shawl

Sea slug

rhinophores

gills

Class BivalviaOysters, clams, mussels ~8,000 species

(1,300 freshwater, rest marine)Benthic filter-feeders (a few exceptions)

• No radula• Enlarged gills

Compressed bodyShell

Two valves Hinged dorsally Completely encloses body

Class Bivalvia / PelecypodaClass Bivalvia / Pelecypoda

Shells have 2 lateral valvesElastic ligamentBody is enclosed by a 2-lobed mantle

Shells have 2 lateral valvesElastic ligamentBody is enclosed by a 2-lobed mantle

(elevation)

Class Bivalvia / PelecypodaClass Bivalvia / Pelecypodahatchet shaped foot in burrowersHead lacks eyes, radula and tentacleshatchet shaped foot in burrowersHead lacks eyes, radula and tentacles

Freshwater clam

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Class Bivalvia

clams, oysters, mussels, scallops soft body between two halves of a hinged

shell

California musselGiant clam

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Class Bivalvia

Aquatic– most marine,

some fresh water no tentacles,

head, radula adductor muscle Large cilia-

covered gills (in most)

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Bivalve shell morphology

Umbo- oldest part of shell– Growth in concentric lines around it

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Valves open by adductor muscle– contraction= closed– relaxing= open

Hinge= mantle secretion of more protein, less calcium carbonate

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Water movement through bivalves

1. incurrent siphon - water into the mantle cavity

2. water circulates over the gills– Gas exchange– Filter feeding

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Locomotion Mostly sedentary/sessile highly developed muscular foot

– often to burrow into sediment– move by slicing-like motion of foot – swim by chattering motion of shell

(scallops)

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Oyster

lower valve is cemented to any object available

Improve water quality

Decrease bank erosion

food

http://www.csc.noaa.gov/scoysters/images/bio/oysters2.jpg

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Pearl Production

Developing pearl

Developing pearl

EpitheliumEpithelium

ShellShell

protective function– foreign substance

between mantle & shell

mantle secretes pearly layers of nacre around substance

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Giant Clam & Burrowing Clam

some= food

Giant clam

Siphon

Burrowing clam

Tridacna (giant clam) - Subphylum Conchifera;

Class Bivalvia

Tridacna (giant clam) - Subphylum Conchifera;

Class Bivalvia

Spondylus (scallop) Subphylum Conchifera;

Class Bivalvia

Spondylus (scallop) Subphylum Conchifera;

Class Bivalvia

S. versicolor

S. princeps

Chlamys (scallop) Subphylum Conchifera;

Class Bivalvia

Chlamys (scallop) Subphylum Conchifera;

Class Bivalvia

C. islandicus

C. swifti

Perna (mussel) Subphylum Conchifera;

Class Bivalvia

Perna (mussel) Subphylum Conchifera;

Class Bivalvia

P. veridis

Crassostrea (oyster) Subphylum Conchifera;

Class Bivalvia

Crassostrea (oyster) Subphylum Conchifera;

Class Bivalvia

Pacific oysters

Atlantic oyster

Anodonta (freshwater clam) – Subphylum Conchifera;

Class Bivalvia

Anodonta (freshwater clam) – Subphylum Conchifera;

Class Bivalvia

A. suborbiculata

A. anatina

Class CephalopodaClass Cephalopoda

Free-swimming Fast moving Active carnivores Elongated body Skeleton may be external, internal or absent Foot developed into prehensile arms or

tentacles

Free-swimming Fast moving Active carnivores Elongated body Skeleton may be external, internal or absent Foot developed into prehensile arms or

tentacles

Octopus arm

Class CephalopodaClass Cephalopoda Well-defined head

Complex eyes

Brain in cartilaginous cranium

(+) radula

Beak-like jaws

Tentacles surrounding mouth

Well-defined head

Complex eyes

Brain in cartilaginous cranium

(+) radula

Beak-like jaws

Tentacles surrounding mouth

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Class Cephalopoda squid, octopus, nautilus,

cuttlefishammonoids

“head foot” Largest, most complex

invertebrates

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most highly developed mollusc– Most active and intelligent

Marine predator– carnivorous

Cuttlefish

Cuttlefish camouflage

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shell reduced/absent & internalized (vestigal) (squid, octopus)

Nautilus- shell Cuttlefish- small, enclosed by mantle

Octopus

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head is well developed - large eyes – Complex eyes (except Nautilus)

Cornea, lens, chambers, retina, iris

Well-developed nervous system - complex brain

Squid

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foot is modified into multiple tentacles with suckers (in some)– Grasp prey– Taste via suckers– Crawling

siphon forces out water: “jet propulsion”

Octopus movement

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squid & octopus possess ink gland which produce melanin ; escape

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Octopus Eight arms with suckers Crawl or eject water from siphon Change skin color Most intelligent invertebrate

– Colorblind, but can be taught different shapes

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Octopus

camouflage

http://www.cephbase.utmb.edu/viddb/vidsrch3.cfm?ID=132&CephID=495

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Some octopi can kill humans: – Blue-ringed octopus

Size of golf ball Bacteria in salivary glands Paralysis, but victim fully conscious

Blue-ringed octopus

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Nautilus Up to 94

tentacles– No suckers

Shell with many gas chambers

Nautilus

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Ammonoids

Extinct– 400 to 65 MYA

Died out with dinosaurs

Loligo (squid) Subphylum Conchifera;

Class Cephalopoda

8 arms and 2 tentacles8 arms and 2 tentacles

mantle

siphon

ctenidia

Sepia (cuttlefish) Class Cephalopoda

Octopus (octopus) – Subphylum Conchifera;

Class Cephalopoda

Octopus (octopus) – Subphylum Conchifera;

Class Cephalopoda

Nautilus (nautiloid) – Subphylum Conchifera;

Class Cephalopoda

Nautilus (nautiloid) – Subphylum Conchifera;

Class Cephalopoda

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Circulatory system of molluscs

Open circulatory system (except Class Cephalopoda)– Open circulatory system

heart pumps hemolymph (blood) through body cavity, b/w cells

No small blood vessels

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Circulatory system of molluscs– Closed circulatory system (Class

Cephalopoda) Blood confined to vessels

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Molluscan reproduction

Mostly dioecious

http://www.biology.ualberta.ca/courses.hp/zool250/Labs/Lab08/Lab08.htm

Long-finned squid- Loligo

Giant squid

Class ScaphopodaClass Scaphopoda

Burrowing and sedentary Shell in one piece Shell opens on both sides With modified conical foot Head is reduced or absent No eyes With radula, jaws and thin tentacles

Burrowing and sedentary Shell in one piece Shell opens on both sides With modified conical foot Head is reduced or absent No eyes With radula, jaws and thin tentacles

Dentalium (Elephant’s tusk shell) Subphylum Conchifera;

Class Scaphopoda

Dentalium (Elephant’s tusk shell) Subphylum Conchifera;

Class Scaphopoda

shellshellanterior

posterior

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Class Scaphopoda– Tooth shells– Long, slender body– Burrows into mud– Shell open at both ends

http://www.ucmp.berkeley.edu/mollusca/scaphs/scaphopoda.html

Digestive system of mollusca

Nervous system of mollusca

Class: CephalopodaIt is a very diverse class, with 600 living species

and more than 7500 fossil species. The class, Cephalopoda, includes the

Chambered Nautilus, cuttlefish, squid, and octopus, as well as fossil ammonite and other fossil forms.

Size varies from planktonic to some as large as sixty feet; e.g., the present day squid, Architeuthis princeps, found in open ocean.

However, most cephalopods are small, and they form a major component of the food web of larger fish and whales.

Dibranchiata Tetrabranchiatae.g. Octopus, Sepia e.g. Nautilus

One pair of gills Two pairs of gills

One pair of kidneys Two pairs of kidneys

One pair of auricles Two pairs of auricles

The shell is internal or absent External large, thin, coiled shell

The arms are 8 to 10 arms, bearing suckers

Numerous tentacles without suckers

The funnel is simple and forms a complete tube

The funnel is formed of 2 lobes (not simple)

Order: Decapoda Order: Octopoda

e.g. Sepia, Loligo e.g. Octopus

Shell is internal Shell is absent

The body is elongated The body is globular

Has a pair of lateral fins Has no fins

8 arms and 2 long tentacles 8 arms

Arms provided with stalked suckers

Arms provided with sessile suckers

Echinoderms are a phylum of marine animals including the sea star and the sand dollar.

Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone.

The phylum contains about 7,000 living species.

The Echinoderms are important both biologically and geologically.

Phylum: Echinodermata

Echinoderms form a well-defined and highly-derived clade of metazoans.

They have attracted much attention due to their extensive fossil record, ecological importance in the marine realm, intriguing adult morphology, unusual biomechanical properties, and experimentally manipulable embryos.

The approximately 7,000 species of extant echinoderms fall into five well-defined clades: Crinoidea (sea lilies and feather stars), Ophiuroidea (basket stars and brittle stars), Asteroidea (starfishes), Echinoidea (sea urchins, sand dollars, and sea biscuits), and Holothuroidea (sea cucumbers).

Approximately 13,000 echinoderm species are known from the fossil record.

Introduction

Economic importance Most humans know the Echinoderms rather from the

unpleasant side: if one finds oneself near the coast, on a rocky shore or reef, one must beware the prick of a sea urchin.

However in the kitchens of some countries,echinoderms are regarded as a delicacy; and for children sea-urchin skeletons are as popular a collecting object as brightly coloured starfish are fascinating.

Around 50,000 tons of sea urchins are captured each year, the gonads of which are consumed particularly in Japan, Peru and in France. Sea cucumbers are also considered a delicacy in some countries of south east Asia.

It does appear that some sea cucumber toxins restrain the growth rate of tumour cells.

The calcareous tests or shells of echinoderms are used as a source of lime by farmers in areas where limestone is unavailable.

1.  Five fold symmetry:  arms or rays occurs in multiple of 5's.

2. Advanced Biological systems:         --Digestive system including mouth, alimentary canal (intestine), and anus.         --Water vascular system: hydraulic system which driven by water and muscular contraction serve to motion of tube feet.  These tube feet, small structures with sucker-like endings, provide for locomotion and or feeding.          -- Reproductive system -- Nervous system          -- Skeleton made of CaCO3 which is developed as discrete plates or segments, each comprising a single crystal of calcite.  This monocrystalline structure is particularly illustrated in the structure of spines of the urchins. 

Characters

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