The Animal Kingdom: The Protostomes

The Animal Kingdom:The Animal Kingdom:The ProtostomesThe Protostomes

Chapter 30Chapter 30

Learning Objective 1Learning Objective 1

• Cite specific examples of the evolutionary Cite specific examples of the evolutionary significance of the significance of the coelomcoelom

Coelom 1Coelom 1

• True True coelomcoelom is a fluid-filled body cavity is a fluid-filled body cavity • completely lined by mesoderm between completely lined by mesoderm between

digestive tube and outer body walldigestive tube and outer body wall

• Allows Allows tube-within-a-tubetube-within-a-tube body planbody plan• body wall is outer tubebody wall is outer tube• inner tube is digestive tubeinner tube is digestive tube

Coelom 2Coelom 2

• An enclosed compartment (or series of An enclosed compartment (or series of compartments) of fluid under pressurecompartments) of fluid under pressure

• Serve as Serve as hydrostatic skeletonhydrostatic skeleton • contracting muscles push against tube of fluidcontracting muscles push against tube of fluid

Coelom 3Coelom 3

• A space in which internal organs developA space in which internal organs develop• including gonadsincluding gonads

• Helps transport materialsHelps transport materials

• Protects internal organsProtects internal organs

KEY CONCEPTSKEY CONCEPTS

• Evolution of the coelom has been Evolution of the coelom has been associated with important innovations in associated with important innovations in body plan, including cephalization, the body plan, including cephalization, the tube-within-a-tube body plan, tube-within-a-tube body plan, compartmentalization, and segmentationcompartmentalization, and segmentation


• Characterize the Characterize the protostomesprotostomes

• Describe their two main evolutionary Describe their two main evolutionary branchesbranches

• Give examples of animals assigned to Give examples of animals assigned to each brancheach branch

ProtostomesProtostomes

• Characterized byCharacterized by• spiral cleavagespiral cleavage• determinate cleavagedeterminate cleavage• development of mouth from blastoporedevelopment of mouth from blastopore

Two Branches of ProtostomesTwo Branches of Protostomes

• LophotrochozoaLophotrochozoa • platyhelminths, nemerteans, mollusks, platyhelminths, nemerteans, mollusks,

annelids, lophophorate phyla, rotifers annelids, lophophorate phyla, rotifers

• EcdysozoaEcdysozoa • nematodes (roundworms) and arthropodsnematodes (roundworms) and arthropods


• Protostomes are a monophyletic group Protostomes are a monophyletic group that gave rise to two major clades: that gave rise to two major clades: Lophotrochozoa and EcdysozoaLophotrochozoa and Ecdysozoa


• What are the distinguishing characteristics What are the distinguishing characteristics of phylum of phylum NemerteaNemertea and phylum and phylum PlatyhelminthesPlatyhelminthes??

• Describe the main classes of phylum Describe the main classes of phylum PlatyhelminthesPlatyhelminthes, giving examples of , giving examples of animals that belong to each classanimals that belong to each class

Phylum Nemertea (Ribbon Worms) 1Phylum Nemertea (Ribbon Worms) 1

• Characterized by Characterized by proboscisproboscis• muscular tube for capturing food, defense muscular tube for capturing food, defense

• Reduced coelom (Reduced coelom (rhynchocoelrhynchocoel))• space surrounding proboscis space surrounding proboscis

Phylum Nemertea (Ribbon Worms) 2Phylum Nemertea (Ribbon Worms) 2

• NemerteansNemerteans have have• tube-within-a-tube body plantube-within-a-tube body plan• complete digestive tract with mouth and anus complete digestive tract with mouth and anus • a circulatory systema circulatory system

NemerteansNemerteans

Phylum Platyhelminthes Phylum Platyhelminthes (Flatworms)(Flatworms) 11

• AcoelomateAcoelomate animals with animals with• bilateral symmetry bilateral symmetry • cephalizationcephalization • 3 definite tissue layers 3 definite tissue layers • well-developed organswell-developed organs

• Many are Many are hermaphroditeshermaphrodites • single animal produces both sperm and eggs single animal produces both sperm and eggs

Phylum Platyhelminthes Phylum Platyhelminthes (Flatworms)(Flatworms) 22

• Ladder-type nervous system Ladder-type nervous system • sense organssense organs• simple brain composed of two simple brain composed of two gangliaganglia• 2 nerve cords that extend the length of body2 nerve cords that extend the length of body

• ProtonephridiaProtonephridia• function in osmoregulation and disposal of function in osmoregulation and disposal of

metabolic wastesmetabolic wastes

3 Classes of3 Classes ofPhylum PlatyhelminthesPhylum Platyhelminthes

• Class Class TurbellariaTurbellaria• free-living flatworms, including free-living flatworms, including planariansplanarians

• Classes Classes TrematodaTrematoda and and Monogenea Monogenea • parasitic parasitic flukesflukes

• Class Class CestodaCestoda• parasitic tapeworms parasitic tapeworms

PlanarianPlanarian

Fig. 30-1 (1), p. 642

Lophotrochozoa

Par

azo

a

Rad

iata

Pla

tyh

elm

inth

es

Nem

erte

a

Mo

llu

sca

An

nel

ida

Lo

ph

op

ho

rate

p

hyl

a

Ro

tife

ra

Ecd

yso

zoa

Deu

tero

sto

mia

Choanoflagellate ancestor

Fig. 30-1ab, p. 642

Ganglia

Auricle

Eyespot

Nerve

Gastrovascular cavity

Pharynx

Sheath surrounding

pharynx

Mouth

1 mm

Auricle

Fig. 30-1c, p. 642

Pharyngeal sheath cavity

Inner muscle layer of pharynx

Pharyngeal cavity

Outer muscle layerMuscle

Epidermis

Adhesive glandSperm

massVentral nerve cords

Muscle layers

Body wall composed of epidermis, circular muscle, and longitudinal muscle

Cilia

Insert “Planarian organ Insert “Planarian organ systems”systems”

planarian_organs_v2.swfplanarian_organs_v2.swf

Parasitic Flukes and TapewormsParasitic Flukes and Tapeworms

• Typically have suckers or hooksTypically have suckers or hooks• for holding on to their hostsfor holding on to their hosts

• Have complicated life cyclesHave complicated life cycles• intermediate hostsintermediate hosts• large numbers of eggslarge numbers of eggs

Parasitic FlukeParasitic Fluke

Fig. 30-2, p. 644

2 Larvae make their way to circulatory system, where they mature. During reproduction, which takes place in veins, male holds female in a long groove.1 Larvae

burrow through skin.

1 mm

7 Finally, fork-tailed larvae (cercariae) develop and leave snail.

Eggs pass into intestine.

3

4 Eggs containing developing embryos are excreted with feces.

Larvae must enter a second host, a freshwater snail. After burrowing into tissues of snail, larvae develop into a form that reproduces asexually.

5 If they find their way to fresh water, the eggs hatch, releasing free-swimming larvae (miracidia).

6

TapewormTapeworm

Insert “Blood fluke life-Insert “Blood fluke life-cycle” and “Tapeworm life cycle” and “Tapeworm life

cycle”cycle”blood_fluke.swfblood_fluke.swf

tapeworm.swftapeworm.swf

Watch the fluke and tapeworm Watch the fluke and tapeworm life cycles by clicking on the life cycles by clicking on the

figures in ThomsonNOW.figures in ThomsonNOW.


• What are the adaptive advantages of What are the adaptive advantages of cephalizationcephalization??

CephalizationCephalization

• Evolution of a headEvolution of a head• concentration of sense organs and nerve cells concentration of sense organs and nerve cells

(simple brain) at anterior end(simple brain) at anterior end• (Flatworms show beginnings of cephalization) (Flatworms show beginnings of cephalization)

• Increases effectiveness of bilateral animalIncreases effectiveness of bilateral animal• to actively find food, shelter, matesto actively find food, shelter, mates• to detect enemiesto detect enemies


• What are the distinguishing characteristics What are the distinguishing characteristics of phylum of phylum MolluscaMollusca and the four molluscan and the four molluscan classes discussed? classes discussed?

• Give examplesGive examples

PhylumPhylum MolluscaMollusca

• Soft-bodied animalsSoft-bodied animals• usually covered by a shell usually covered by a shell

• Ventral foot Ventral foot • for locomotionfor locomotion

• Mantle Mantle • covers covers visceral massvisceral mass (body organs) (body organs)

MollusksMollusks

• Most have Most have open circulatory systemopen circulatory system • Cephalopods have Cephalopods have closed circulatory systemclosed circulatory system

• Most have rasplike Most have rasplike radularadula for feeding for feeding• Bivalves are suspension feedersBivalves are suspension feeders

• Most marine mollusks have free-Most marine mollusks have free-swimming, ciliated swimming, ciliated trochophore larvatrochophore larva

Insert “Molluscan Insert “Molluscan classes”classes”

mollusk_classes.swfmollusk_classes.swf

Trochophore LarvaTrochophore Larva

Fig. 30-7, p. 648

Digestive tract

Cilia

Mouth

Nephridium

Mesodermal cells

Anus

ClassClass PolyplacophoraPolyplacophora

• Includes marine Includes marine chitonschitons• Shells consist of 8 overlapping platesShells consist of 8 overlapping plates

Fig. 30-6a, p. 647

ShellDigestive

tract

Class Polyplacophora

ClassClass GastropodaGastropoda

• Largest group of mollusksLargest group of mollusks• snails, slugs, and their relatives snails, slugs, and their relatives

• Body undergoes Body undergoes torsiontorsion• a twisting of the visceral mass a twisting of the visceral mass

Fig. 30-6b, p. 647

Shell

Digestive tractFoot

Class Gastropoda

Insert “Snail body plan”Insert “Snail body plan”

snail_body_plan.swfsnail_body_plan.swf

TorsionTorsion

Insert “Torsion in Insert “Torsion in gastropods”gastropods”

torsion.swftorsion.swf

ClassClass BivalviaBivalvia

• Includes aquatic clams, scallops, oystersIncludes aquatic clams, scallops, oysters

• Two-part shell Two-part shell • hinged dorsally hinged dorsally • encloses bodies encloses bodies

• Suspension feeders Suspension feeders

Fig. 30-6c, p. 647

Shell

FootDigestive

tract

Class Bivalva

ClamClam

Fig. 30-10, p. 649

Digestive gland Heart

DORSAL MetanephridiumStomach

IntestineEsophagus

Ganglion

Anterior adductor muscle Excurrent

siphon

Mouth

Palp

Gill—partially cutPedal

ganglion

Foot ShellIntestine

VENTRAL

Gonad

Posterior adductor muscleAnus

Incurrent siphon

Mantle

Insert “Clam body plan”Insert “Clam body plan”

clam.swfclam.swf

ClassClass CephalopodaCephalopoda

• Includes squids, octopods, Includes squids, octopods, Nautilus Nautilus

• Active, predatory swimmers Active, predatory swimmers

• Tentacles surround the mouthTentacles surround the mouth• located in the large headlocated in the large head

Fig. 30-6d, p. 647

Internal shell

Tentacles (modified foot)

Digestive tract

Class Cephalopoda


• What are the distinguishing characteristics What are the distinguishing characteristics of phylum of phylum AnnelidaAnnelida and the three annelid and the three annelid classes discussed? classes discussed?

• Give examplesGive examples

PhylumPhylum AnnelidaAnnelida (Segmented Worms)(Segmented Worms)

• Aquatic worms, earthworms, leeches Aquatic worms, earthworms, leeches

• Conspicuously long bodies Conspicuously long bodies

• SegmentationSegmentation• both internally and externallyboth internally and externally

• Large, compartmentalized coelomLarge, compartmentalized coelom• serves as hydrostatic skeletonserves as hydrostatic skeleton

AnnelidsAnnelids

Fig. 30-11 (a-c), p. 650

Setae Mouth

ClitellumSuckers

Parapodia

Anus

Class Polychaeta Class Oligochaeta Class Hirudinea

Stepped Art

Fig. 30-11 (a-c), p. 650

Mouth

Clitellum

Class Oligochaeta

Setae

Anus

Parapodia

Class Polychaeta

Lophotrochozoa

Pa

razo

a

Ra

dia

ta

Pla

tyh

elm

inth

es

Ne

me

rte

a

Mo

llu

sc

a

An

ne

lid

a

Lo

ph

op

ho

rate

p

hy

la

Ro

tife

ra

Ec

dy

so

zoa

De

ute

ros

tom

ia


Suckers

Class Hirudinea

EarthwormEarthworm

Fig. 30-12a, p. 651

Clitellum

Intestine

Esophagus

Pharynx

Dorsal vesselVentral vessel

Longitudinal MouthMuscles

Circular Nerve cord Cerebral ganglia

Septa

Gizzard Crop

Fig. 30-12b, p. 651

Dorsal blood vesselIntestine

Metanephridia

Coelom

Ventral blood vessel

Nerve cord

Insert “Earthworm body Insert “Earthworm body plan”plan”

earthworm_v2.swfearthworm_v2.swf

LeechesLeeches

ClassClass PolychaetaPolychaeta

• Marine worms with Marine worms with parapodiaparapodia• appendages for locomotion, gas exchangeappendages for locomotion, gas exchange

• Parapodia have many Parapodia have many setae setae

• Well-defined head with sense organs Well-defined head with sense organs • unlike other annelids unlike other annelids

Class OligochaetaClass Oligochaeta

• EarthwormsEarthworms

• Characterized by few short Characterized by few short setaesetae per per segmentsegment

• Body divided into > 100 segmentsBody divided into > 100 segments• separated internally by separated internally by septasepta

ClassClass HirudineaHirudinea

• Leeches Leeches

• Characterized by absence of Characterized by absence of setaesetae and and appendagesappendages

• Parasitic leeches have suckersParasitic leeches have suckers• for holding on to their hostfor holding on to their host


• What are the distinguishing characteristics What are the distinguishing characteristics of the of the lophophorate phylalophophorate phyla??

The Lophophorate PhylaThe Lophophorate Phyla

• MMarine animals with a arine animals with a lophophorelophophore• brachiopods, phoronids,brachiopods, phoronids, bryozoans bryozoans

• LophophoreLophophore• ciliated ring of tentacles surround the mouth ciliated ring of tentacles surround the mouth • specialized to capture particles in waterspecialized to capture particles in water

LophophoratesLophophorates

• Phylum Phylum Brachiopoda Brachiopoda

• Phylum Phylum PhoronidaPhoronida

• Phylum Phylum Bryozoa Bryozoa

Fig. 30-14 (1), p. 653

Lophotrochozoa

Par

azo

a

Rad

iata

Pla

tyh

elm

inth

es

Nem

erte

a

Mo

llu

sca

An

nel

ida

Lo

ph

op

ho

rate

p

hyl

a

Ro

tife

ra

Ecd

yso

zoa

Deu

tero

sto

mia


Phylum RotiferaPhylum Rotifera

Fig. 30-15 (1), p. 654

Lophotrochozoa

Par

azo

a

Rad

iata

Pla

tyh

elm

inth

es

Nem

erte

a

Mo

llu

sca

An

nel

ida

Lo

ph

op

ho

rate

p

hyl

a

Ro

tife

ra

Ecd

yso

zoa

Deu

tero

sto

mia


Fig. 30-15a, p. 654

150 µm

Fig. 30-15b, p. 654

Crown of cilla

MouthPharynx (grinding organ)

Digestive glands

Stomach Reproductive organ

ProtonephridiumIntestine

Cuticle and epidermis

Anus

Bladder

Eyespot


• What are the distinguishing characteristics What are the distinguishing characteristics of phylum of phylum NematodaNematoda??

Phylum Nematoda (Roundworms)Phylum Nematoda (Roundworms)

• Highly successful Highly successful ecdysozoansecdysozoans

• Pseudocoelom Pseudocoelom

• Body covered by tough Body covered by tough cuticlecuticle • helps prevent desiccation helps prevent desiccation

Phylum Nematoda (Roundworms)Phylum Nematoda (Roundworms)

• Parasitic nematodes in humansParasitic nematodes in humans• Ascaris Ascaris • hookworms hookworms • trichina worms trichina worms • pinwormspinworms

AscarisAscaris

Fig. 30-17, p. 656

MouthPharynx

Dorsal nerve

Excretory canal

PharynxMuscle of pharynx wallExcretory

gland

Pseudocoelom

UterusOvary

Intestine

Vulva Excretory canal

Muscle layer

Epidermis Ventral nerve

Cuticle (b) Cross section

Anus

(a) Longitudinal section


• What are the distinguishing characteristics What are the distinguishing characteristics of phylum of phylum Arthropoda?Arthropoda?

• Distinguish among the subphyla and Distinguish among the subphyla and classes of this phylum classes of this phylum

• Give examples of animals that belong to Give examples of animals that belong to each groupeach group

Phylum Arthropoda 1Phylum Arthropoda 1

• Segmented animals with Segmented animals with paired, jointed paired, jointed appendagesappendages

• Armorlike Armorlike exoskeletonexoskeleton of chitin of chitin

• MoltingMolting necessary for arthropod to grow necessary for arthropod to grow

Phylum Arthropoda 2Phylum Arthropoda 2

• Open circulatory systemOpen circulatory system• dorsal heart, pumps dorsal heart, pumps hemolymphhemolymph

• Aquatic forms have gills for gas exchangeAquatic forms have gills for gas exchange

• Terrestrial forms have either Terrestrial forms have either tracheaetracheae or or book lungsbook lungs


• The most biologically successful The most biologically successful protostomes in terms of diversity and protostomes in terms of diversity and numbers are the mollusks and the numbers are the mollusks and the arthropodsarthropods

TrilobitesTrilobites

• Extinct marine arthropodsExtinct marine arthropods• covered by hard, segmented shellcovered by hard, segmented shell

• Each segment had a pair of Each segment had a pair of biramous biramous appendagesappendages with two jointed branches with two jointed branches

• inner walking leginner walking leg• outer gill branchouter gill branch

TrilobitesTrilobites

Fig. 30-19 (1), p. 658

Ecdysozoa

Par

azo

a

Rad

iata

Lo

ph

otr

och

ozo

a

Nem

ato

da

Art

hro

po

da

Deu

tero

sto

mia


Fig. 30-19ab, p. 658

Antenna

Head

Eye

Gill

Lateral lobe

Median lobe

(a) Dorsal view of a trilobite. (b) Ventral view.

SubphylumSubphylum MyriapodaMyriapoda

• 2 Classes2 Classes• ChilopodaChilopoda (centipedes) (centipedes) • DiplopodaDiplopoda (millipedes) (millipedes)

• Uniramous Uniramous (unbranched) (unbranched) appendagesappendages

• Single pair of antennaeSingle pair of antennae

MyriapodsMyriapods

SubphylumSubphylum Chelicerata 1Chelicerata 1

• MerostomesMerostomes (horseshoe crabs) and (horseshoe crabs) and Arachnids Arachnids (spiders, mites, and relatives)(spiders, mites, and relatives)

• Body with cephalothorax and abdomenBody with cephalothorax and abdomen

• 6 pairs of uniramous, jointed appendages6 pairs of uniramous, jointed appendages• 4 pairs serve as legs4 pairs serve as legs

SubphylumSubphylum Chelicerata 2Chelicerata 2

• First appendages are First appendages are cheliceraechelicerae• second are second are pedipalpspedipalps

• Appendages adapted for manipulation of Appendages adapted for manipulation of food, locomotion, defense, copulationfood, locomotion, defense, copulation

• No antennae, no mandiblesNo antennae, no mandibles

CheliceratesChelicerates

Subphylum Crustacea 1Subphylum Crustacea 1

• Lobsters, crabs, shrimp, pill bugs, Lobsters, crabs, shrimp, pill bugs, barnaclesbarnacles

• Body with cephalothorax and abdomen Body with cephalothorax and abdomen

• Most have five pairs of walking legsMost have five pairs of walking legs

• Appendages are biramousAppendages are biramous

Subphylum Crustacea 2Subphylum Crustacea 2

• Two pairs of Two pairs of antennaeantennae • sense taste and touch sense taste and touch

• Third appendages are Third appendages are mandiblesmandibles • for chewing for chewing

• Two pairs of Two pairs of maxillaemaxillae• posterior to mandiblesposterior to mandibles• manipulate and hold foodmanipulate and hold food

CrustaceansCrustaceans

LobsterLobster

Fig. 30-23a, p. 661

Cephalothorax

Abdomen Thorax Head

EyeFifth walking leg

Fig. 30-23b, p. 661

Tail fan Fifth walking leg

Second walkingleg

Third maxilliped

MouthCheliped

First antenna

Second antenna

Swimmerets First swimmeret (used by male in copulation)

SubphylumSubphylum Hexapoda Hexapoda

• Includes class Includes class InsectaInsecta• articulated, tracheated hexapodsarticulated, tracheated hexapods

Fig. 30-24a, p. 661

Head Thorax Abdomen Forewing

Antenna

Sound receptor Spiracles Hindwing

(a) External structure. Note the three pairs of segmented legs.

Compound eye

Simple eye

InsectsInsects

• Body with head, thorax, and abdomenBody with head, thorax, and abdomen• Uniramous appendagesUniramous appendages• Single pair of antennaeSingle pair of antennae• Tracheae for gas exchangeTracheae for gas exchange• Malpighian tubulesMalpighian tubules for excretion for excretion

Digestive gland Heart Anus

Brain

Nerve cord Intestine

Malpighian tubules Genital opening

Ovary

(b) Internal Anatomy.

GrasshopperGrasshopper


• What adaptations have contributed to the What adaptations have contributed to the biological success of biological success of insectsinsects??

Insect Adaptations 1Insect Adaptations 1

• Versatile exoskeletonVersatile exoskeleton• SegmentationSegmentation• Specialized jointed appendages Specialized jointed appendages • Highly developed sense organsHighly developed sense organs• Ability to fly Ability to fly

Insert “Insect head parts”Insert “Insect head parts”

insect_heads.swfinsect_heads.swf


• MetamorphosisMetamorphosis• transition from one developmental form to transition from one developmental form to

anotheranother• reduces intraspecific competition reduces intraspecific competition

MetamorphosisMetamorphosis

Insert “Insect Insert “Insect development”development”

insect_devt.swfinsect_devt.swf


• Insects have developedInsects have developed• effective reproductive strategieseffective reproductive strategies• effective mechanisms for defense, offenseeffective mechanisms for defense, offense• ability to communicateability to communicate


• The remarkable biological success of the The remarkable biological success of the insects can be attributed to the evolution insects can be attributed to the evolution of complex body plans and life cycles, for of complex body plans and life cycles, for example, their exoskeleton, segmentation, example, their exoskeleton, segmentation, specialized jointed appendages, ability to specialized jointed appendages, ability to fly, and metamorphosisfly, and metamorphosis

Explore the body plans of the Explore the body plans of the protostomes by clicking on the protostomes by clicking on the

figures in ThomsonNOW.figures in ThomsonNOW.

Documents

The Animal Kingdom: The Protostomes