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CHAPTER 12CHAPTER 12CHAPTER 12CHAPTER 12Sponges andSponges andPlacozoansPlacozoans

Sponges andSponges andPlacozoansPlacozoans

Powerpoint revised by Franklyn Tan Te

Copyright 2013 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

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A Caribbean demosponge, Aplysina fistularis.

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Origins of MulticellularityOrigins of Multicellularity

Cells are the elementary units of lifeCells are the elementary units of life NaturesNatures experiments with largerexperiments with larger

organisms without cellular differentiationorganisms without cellular differentiationareare limitedlimited such that large, single celledsuch that large, single celledmarine algae aremarine algae are rarerare

SpongesSponges are theare the simplest multicellularsimplest multicellularanimals but theiranimals but their ccell assemblages areell assemblages aredistinctdistinct from other metazoans.from other metazoans.

Sponges have cells embedded in anSponges have cells embedded in anextracellular matrix supported by aextracellular matrix supported by askeletonskeleton with needlewith needle--likelike spicules andspicules andprotein.protein.12-3

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Origins of MulticellularityOrigins of Multicellularity

Increasing the size of a cell causesIncreasing the size of a cell causesproblems of exchanging molecules withproblems of exchanging molecules withthe environment.the environment. MulticellularityMulticellularity prevents surfaceprevents surface--toto--massmass

problems as smaller units greatly increaseproblems as smaller units greatly increasesurface area for metabolic activitiessurface area for metabolic activities

HHighly adaptive towardsighly adaptive towards larger body sizelarger body size Sponges neither look like or behave asSponges neither look like or behave as

animals but molecular evidenceanimals but molecular evidence demonstratesdemonstratesthat they are phylogenetically grouped withthat they are phylogenetically grouped withanimalsanimals

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Origin of MetazoaOrigin of Metazoa Evolution of the Metazoa (animals)Evolution of the Metazoa (animals)

Eukaryotic cells evolved and diversifiedEukaryotic cells evolved and diversifiedinto many lineages that led to modern dayinto many lineages that led to modern daydescendantsdescendants Includes allIncludes all unicellular protozoans, colonialunicellular protozoans, colonial

and multicellular plants, animals, and fungiand multicellular plants, animals, and fungi Multicellular organisms were collectivelyMulticellular organisms were collectively

calledcalled metazoansmetazoans and are now alsoand are now alsotermedtermed animalsanimals

Metazoans are placed in theMetazoans are placed in the OpisthokontOpisthokontcladeclade which include fungi,which include fungi,choanoflagellates,choanoflagellates, and other groupsand other groups

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Origin of MetazoaOrigin of Metazoa ChoanoflagellatesChoanoflagellates

Solitary or colonial aquatic eukaryotesSolitary or colonial aquatic eukaryotes Each cell has a flagellum surrounded by a collarEach cell has a flagellum surrounded by a collar

of microvilliof microvilli Flagellum beats and draws water into collarFlagellum beats and draws water into collar

where the microvilli collect particles likewhere the microvilli collect particles likebacteriabacteria

Most are sessileMost are sessile but one species attaches tobut one species attaches tofloating diatom colonies and feed midwaterfloating diatom colonies and feed midwater

Strongly resemble sponge feeding cells calledStrongly resemble sponge feeding cells calledchoanocyteschoanocytes, which have been argued to be, which have been argued to beancestral to choanoflagellatesancestral to choanoflagellates

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Evidences of common ancestry betweenEvidences of common ancestry betweenChoanoflagellates andChoanoflagellates and MMetazoansetazoans By comparing the genomes or proteomes ofBy comparing the genomes or proteomes of

sponges with more complex taxa, scientistssponges with more complex taxa, scientistscan discover whatcan discover what cell transmitterscell transmitters orormorphogensmorphogens the first metazoans possessed.the first metazoans possessed.

Shared characteristics would have beenShared characteristics would have beeninherited from the most recent commoninherited from the most recent commonancestor of animals.ancestor of animals.

Molecular phylogeny indicates that colonialMolecular phylogeny indicates that colonialbodies evolved early in the lineage.bodies evolved early in the lineage.

Origin of MetazoaOrigin of Metazoa

Origin of MetazoaOrigin of Metazoa

Recent researchRecent research indicatesindicates proteins used byproteins used bycolonial choanoflagellates forcolonial choanoflagellates for cellcellcommunication and adhesioncommunication and adhesion arearehomologous to those that metazoans use inhomologous to those that metazoans use incellcell--toto--cell signaling.cell signaling.

Sponge genome contains elements thatSponge genome contains elements thatcode forcode for regulatory pathwaysregulatory pathways of moreof morecomplex metazoanscomplex metazoans

Sponges have proteins that code forSponges have proteins that code for spatialspatialpatterningpatterning that specify anterior andthat specify anterior andposterior pole of larvae.posterior pole of larvae.

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Origin of MetazoaOrigin of Metazoa Sponges today are less complex than theirSponges today are less complex than their

ancestorsancestors Sponges have simple bodies composed ofSponges have simple bodies composed of

aggregates of several cell types held togetheraggregates of several cell types held togetherby extracellular matrixby extracellular matrix

Sponge bodies are not symmetrical and haveSponge bodies are not symmetrical and haveno mouth or digestive tractno mouth or digestive tract

Placozoans share features with otherPlacozoans share features with otheranimal groups.animal groups. Have small nuclear genome and the largestHave small nuclear genome and the largest

mitochondrial genome in the animal kingdommitochondrial genome in the animal kingdom Placozoan bodies are as puzzling as sponges:Placozoan bodies are as puzzling as sponges:

they also have no heads or tailsthey also have no heads or tails12-9

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Phylum PoriferaPhylum Porifera General Features of SpongesGeneral Features of Sponges

Mostly sessileMostly sessile Body designed for efficient aquatic filter feedingBody designed for efficient aquatic filter feeding PoriferaPorifera meansmeans porepore--bearing;bearing; sacsac--like bodieslike bodies

are perforated by many poresare perforated by many pores Use flagellated collar cells, orUse flagellated collar cells, or choanocytes,choanocytes, toto

move water to bring food and oxygen whilemove water to bring food and oxygen whileremoving wastesremoving wastes

MostMost of the 8600 sponges are marine, found in allof the 8600 sponges are marine, found in allseas and all depths, while few live in brackishseas and all depths, while few live in brackishwater and 150 live in fresh waterwater and 150 live in fresh water

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12-11Figure 12.1 Some growth habits and forms of sponges.

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Figure 12.2 Sponge choanocytes have a collar of microvillisurrounding a flagellum.

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Phylum PoriferaPhylum Porifera SpongesSponges vary in sizevary in size from a fewfrom a few

millimeters to over 2 meters in diametermillimeters to over 2 meters in diameter Many species areMany species are brightly coloredbrightly colored becausebecause

of pigments in dermal cellsof pigments in dermal cells EmbryosEmbryos are freeare free--swimming whileswimming while adultadult

spongessponges always attachedalways attached Some appear radially symmetrical but manySome appear radially symmetrical but many

are irregular in shapeare irregular in shape Some stand erect, some are branched, andSome stand erect, some are branched, and

others are encrustingothers are encrusting Growth patterns depend on shape ofGrowth patterns depend on shape of

substratum, direction of water, speed of flowsubstratum, direction of water, speed of flowand availability of spaceand availability of space

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Phylum PoriferaPhylum Porifera Many animals like crabs, nudibranchs,Many animals like crabs, nudibranchs,

fish, and other species do live asfish, and other species do live ascommensals or parasitescommensals or parasites in or on spongesin or on sponges

Sponges can also grow on a variety ofSponges can also grow on a variety ofother living organisms with some crabsother living organisms with some crabsusing sponges for camouflage andusing sponges for camouflage andprotectionprotection

Sponges and microorganisms living onSponges and microorganisms living onthem often have athem often have a noxious odor andnoxious odor andproduce a variety of bioactive compoundsproduce a variety of bioactive compounds Certain sponge extracts have manifestedCertain sponge extracts have manifested

medical and pharmaceutical effectiveness.medical and pharmaceutical effectiveness.

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Phylum PoriferaPhylum Porifera Skeletal structure of a sponge can beSkeletal structure of a sponge can be fibrousfibrous

and/or rigidand/or rigid consisting ofconsisting of calcareous orcalcareous orsiliceous spiculessiliceous spicules Fibrous portion comes from collagen proteinFibrous portion comes from collagen protein

fibrils in intercellular matrixfibrils in intercellular matrix There are several types of collagen, which vary inThere are several types of collagen, which vary in

chemical composition; sponges containchemical composition; sponges contain sponginspongin Composition and shape the spicules form theComposition and shape the spicules form the

basis of sponge classificationbasis of sponge classification ModernModern materials sciencematerials science view spicules forview spicules for

possiblepossible nanoparticle productsnanoparticle products The simplistic exterior of sponges often maskThe simplistic exterior of sponges often mask

their chemical and functional sophisticationtheir chemical and functional sophistication

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Figure 12.3 Diverse forms of spicules that support a sponge body.

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Phylum PoriferaPhylum Porifera Sponges date back to theSponges date back to the early Cambrian andearly Cambrian and

maybe even Precambrian periodmaybe even Precambrian period Traditionally grouped in three classes based onTraditionally grouped in three classes based on

spicules and chemical compositionspicules and chemical compositionCalcarea:Calcarea: calcium carbonate spicules withcalcium carbonate spicules with

one, three, or four raysone, three, or four raysHexactinellids:Hexactinellids: glass sponges with sixglass sponges with six--rayedrayed

siliceous spiculessiliceous spiculesDemospongiae:Demospongiae: siliceous spicules around ansiliceous spicules around an

axial filament, spongin fibers, or bothaxial filament, spongin fibers, or both HomoscleromorphaHomoscleromorpha, was formed to contain, was formed to contain

sponges without a skeleton or with siliceoussponges without a skeleton or with siliceousspicules without an axial filamentspicules without an axial filament

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Figure 12.4 Cladogram depicting evolutionary relationships among thefour classes of sponges.

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Phylum PoriferaPhylum Porifera Form and FunctionForm and Function

Body openings consist of small incurrentBody openings consist of small incurrentpores orpores or dermal ostiadermal ostia in the outer layer ofin the outer layer ofcells calledcells called pinacodermpinacoderm

Sponges feed by collecting suspendedSponges feed by collecting suspendedparticles from the water through internalparticles from the water through internalcanal systemscanal systems Water is directed past the choanocytes, whichWater is directed past the choanocytes, which

are flagellated collar cells that keep the currentare flagellated collar cells that keep the currentflowing via beating of flagellaflowing via beating of flagella

Microvilli in the collar trap and phagocytizeMicrovilli in the collar trap and phagocytizefood particles that pass by.food particles that pass by.

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Phylum PoriferaPhylum Porifera Sponges nonSponges non--selectively consume foodselectively consume food

particles (detritus, plankton, and bacteria)particles (detritus, plankton, and bacteria) The smallest particles (80%) are taken intoThe smallest particles (80%) are taken into

choanocytes bychoanocytes by phagocytosisphagocytosis Protein molecules may be taken in byProtein molecules may be taken in by

pinocytosispinocytosis Two other cell types,Two other cell types, pinacocytespinacocytes andand

archaeocytes,archaeocytes, facilitate feedingfacilitate feeding Dissolved nutrients can also beDissolved nutrients can also be absorbedabsorbed byby

spongessponges Efficiency of food capture is dependent onEfficiency of food capture is dependent on

water movement through the sponge bodywater movement through the sponge body

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Phylum PoriferaPhylum Porifera Three types of sponge body designsThree types of sponge body designs

AsconoidsAsconoids SimplestSimplest body organizationbody organization Small and tubeSmall and tube--shaped to allow water to flowshaped to allow water to flow

directly across cells so nodirectly across cells so no dead spacedead space Choanocytes are in a large internal chamber, theChoanocytes are in a large internal chamber, the

spongocoelspongocoel Choanocyte flagella pull water through theChoanocyte flagella pull water through the

pores and extract food particlespores and extract food particles Used water is expelled through a large singleUsed water is expelled through a large single

osculumosculum AllAll CalcareaCalcarea are asconoidsare asconoids

Leucosolenia sp.Leucosolenia sp. andand Clathrina sp,Clathrina sp, for examplefor example

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Figure 12.5 Threetypes of spongestructure.

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Figure 12.6 Clathrina canariensis (class Calcarea) is a commonAsconoid on Caribbean reefs.

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Phylum PoriferaPhylum Porifera SyconoidsSyconoids

Resemble asconoids butResemble asconoids but larger and with alarger and with athicker more complex body wallthicker more complex body wall

Body wall is folded outwards withBody wall is folded outwards with choanocytechoanocyte--lined radial canalslined radial canals that empty intothat empty into spongocoelspongocoel Water enters through dermal ostia and moveWater enters through dermal ostia and move

into tiny openings calledinto tiny openings called prosopyles into theprosopyles into theradial canalsradial canals

Food is ingested byFood is ingested by choanocyteschoanocytes and usedand usedwater is pumped through internal poreswater is pumped through internal porescalledcalled apopylesapopyles then outwards via osculumthen outwards via osculum

SpongocoelSpongocoel is lined withis lined with epithelial cellsepithelial cells ratherratherthan choanocytes as in asconoidsthan choanocytes as in asconoids

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Phylum PoriferaPhylum Porifera Developmental evidence of being derivedDevelopmental evidence of being derived

from asconoid ancestorsfrom asconoid ancestors Syconoids pass through an asconoid stage inSyconoids pass through an asconoid stage in

development but do not form highly brancheddevelopment but do not form highly branchedcoloniescolonies

Flagellated canals form byFlagellated canals form by evagination of theevagination of thebody wallbody wall

Syconoid body plan is not homologous amongSyconoid body plan is not homologous amongall sponges that have itall sponges that have it

ClassesClasses CalcareaCalcarea andand HexactinellidaHexactinellida havehavesyconoid species (ex:syconoid species (ex: Sycon sp.Sycon sp.))

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Figure 12.7 Cross section through wall of sponge Syconsp., showing choanocytes in canals within the wall but donot line spongocoel.

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Phylum PoriferaPhylum Porifera LeuconoidsLeuconoids

Most complexMost complex and larger, for more foodand larger, for more food--collecting regionscollecting regions

These regions have choanocytes lining in smallThese regions have choanocytes lining in smallchambers that effectively filter all water presentchambers that effectively filter all water present

Clusters of flagellated chambersClusters of flagellated chambers are filled fromare filled fromincurrent canalsincurrent canals and dischargeand discharge to excurrentto excurrentcanalscanals which lead to osculumwhich lead to osculum

After food is removed, used water is pooled toAfter food is removed, used water is pooled toform an exit stream that leaves through an exitform an exit stream that leaves through an exitpore at very high velocitypore at very high velocity

This high rate of exit flow prevents the spongeThis high rate of exit flow prevents the spongefrom refrom re--filtering used water and wastesfiltering used water and wastes

Most sponges are leuconoid typeMost sponges are leuconoid type

Phylum PoriferaPhylum Porifera The leuconoid system has high adaptiveThe leuconoid system has high adaptive

value to efficiently meet high foodvalue to efficiently meet high fooddemands of larger body sizedemands of larger body size Has the highest proportion of flagellatedHas the highest proportion of flagellated

surface per volume of cell tissuesurface per volume of cell tissue More collar cells can filter more particlesMore collar cells can filter more particles Water flow slows down inside due to greaterWater flow slows down inside due to greater

surface area within the chamberssurface area within the chambers Large sponges filter 1500 liters of water perLarge sponges filter 1500 liters of water per

day for maximum food collectionday for maximum food collection The leuconoid system has evolvedThe leuconoid system has evolved

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Figure 12.8 This orange demosponge, Mycale laevis, often growsbeneath plate-like colonies of the stony coral Montastrea annularis.

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Phylum PoriferaPhylum Porifera Types of Cells in SpongesTypes of Cells in Sponges

Sponge cells are arranged in a gelatinousSponge cells are arranged in a gelatinousextracellular matrix calledextracellular matrix called mesohyl ormesohyl ormesenchymemesenchyme The connective tissue of sponges found inThe connective tissue of sponges found in

fibrils, skeletal elements, and amoeboid cellsfibrils, skeletal elements, and amoeboid cells Absence of organs requires that allAbsence of organs requires that all

fundamental processes occur at thefundamental processes occur at theindividual cell levelindividual cell level Respiration and excretion via diffusion andRespiration and excretion via diffusion and

water regulation via contractile vacuoles in thewater regulation via contractile vacuoles in thearchaeocytes and choanocytesarchaeocytes and choanocytes

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Phylum PoriferaPhylum Porifera

Visible activities seen in sponges includeVisible activities seen in sponges includeslight alterations in shape, localslight alterations in shape, localcontraction, propagating contractions, andcontraction, propagating contractions, andclosing and opening of incurrent andclosing and opening of incurrent andexcurrent poresexcurrent pores

Sponges can close their osculum due toSponges can close their osculum due toheavy sediment loadheavy sediment load Movements occur very slowly but they suggestMovements occur very slowly but they suggest

a whole body response in organisms lackinga whole body response in organisms lackingcomplex organization above the cellular levelcomplex organization above the cellular level

Apparently excitation spreads from cell to cellApparently excitation spreads from cell to cellby mechanical stimuli and signaling moleculesby mechanical stimuli and signaling moleculeslike hormones or via electrical impulseslike hormones or via electrical impulses12-31

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Figure 12.9 Small section through sponge wall, showingfour types of sponge cells.

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Phylum PoriferaPhylum Porifera ChoanocytesChoanocytes

Oval cells with one end embedded inOval cells with one end embedded in mesohylmesohyland exposed end has oneand exposed end has one flagellumflagellum surroundedsurroundedby aby a collarcollar CollarCollar consists of microvilli connected toconsists of microvilli connected to

each other by fine microfibrilseach other by fine microfibrils Forms aForms a fine filtering devicefine filtering device to strain foodto strain food Particles too large to enter collar are trappedParticles too large to enter collar are trapped

in mucous and slide down to basein mucous and slide down to base to beto bephagocytizedphagocytized

Food is passed toFood is passed to archaeocytesarchaeocytes forforintracellular digestion with no need for gutintracellular digestion with no need for gutcavitycavity

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Figure 12.10 Food trapping by sponge cells. A) Cutaway section ofcanals showing direction of water flow. B) Two choanocytes, and C)structure of the collar.

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Phylum PoriferaPhylum Porifera ArchaeocytesArchaeocytes

Amoeboid cellsAmoeboid cells that move about in thethat move about in themesohyl with many functionsmesohyl with many functions

Phagocytize particles in thePhagocytize particles in the pinacodermpinacoderm Receive particles for digestion fromReceive particles for digestion from

choanocyteschoanocytes Can differentiate into many other moreCan differentiate into many other more

specialized cell typesspecialized cell types Sclerocytes:Sclerocytes: secrete spiculessecrete spicules Spongocytes:Spongocytes: secrete sponginsecrete spongin Collencytes:Collencytes: secrete fibrillarsecrete fibrillar collagencollagen Lophocytes:Lophocytes: secrete large amounts ofsecrete large amounts of

collagencollagen

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Phylum PoriferaPhylum Porifera

PinacocytesPinacocytes Thin, flat, epithelialThin, flat, epithelial--like cells that cover thelike cells that cover the

exterior and interior surfaces of spongesexterior and interior surfaces of spongesalmost like real tissuesalmost like real tissues

FormForm pinacodermpinacoderm with a variety of intercellularwith a variety of intercellularjunctions but no basal membrane for mostjunctions but no basal membrane for mostspongessponges

Ingest food by phagocytosis and areIngest food by phagocytosis and arecontractilecontractile to regulate surface area of spongeto regulate surface area of sponge

FormForm myocytesmyocytes that are circular bands aroundthat are circular bands aroundoscula and help regulate flow of wateroscula and help regulate flow of water

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Phylum PoriferaPhylum Porifera Cell Independence: Regeneration andCell Independence: Regeneration and

Somatic EmbryogenesisSomatic Embryogenesis Sponges have a great ability to regenerateSponges have a great ability to regenerate

lost parts and repair injurieslost parts and repair injuries Complete reorganization of the structureComplete reorganization of the structure

and function of participating cells or bitsand function of participating cells or bitsof tissue occurs inof tissue occurs in somatic embryogenesissomatic embryogenesis

Process of reorganization differs inProcess of reorganization differs insponges of differing complexitysponges of differing complexity

Regeneration following fragmentation isRegeneration following fragmentation isone means ofone means of asexual reproductionasexual reproduction

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Phylum PoriferaPhylum Porifera Types of Asexual reproductionTypes of Asexual reproduction

FragmentationFragmentation Sponge breaks into parts that are capable ofSponge breaks into parts that are capable of

forming a completely new spongeforming a completely new sponge BBud formationud formation

External budsExternal buds Small individuals that break off fromSmall individuals that break off from

parents that have reached a certain sizeparents that have reached a certain size Internal buds or gemmulesInternal buds or gemmules

Formed by archaeocytes that collect inFormed by archaeocytes that collect inmesohylmesohyl and coated with tough spongin andand coated with tough spongin andspicules that can survive harshspicules that can survive harshenvironmental conditionsenvironmental conditions

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Phylum PoriferaPhylum Porifera How gemmules work?How gemmules work?

When parent sponge dies, gemmules surviveWhen parent sponge dies, gemmules surviveand remain dormant during the harshand remain dormant during the harshsituationssituations

Live cells within gemmules escape throughLive cells within gemmules escape throughspecial opening called micropyles and developspecial opening called micropyles and developinto new spongesinto new sponges

Gemmulation is a adaptation to changingGemmulation is a adaptation to changingseasons and for colonization of new habitatsseasons and for colonization of new habitats

Gemmules are controlled by weather, internalGemmules are controlled by weather, internalchemicals, and by remaining inside the parentchemicals, and by remaining inside the parentsponge.sponge.

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Figure 12.11 Section through a gemmule of a freshwatersponge (Spongillidae).

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Phylum PoriferaPhylum Porifera Sexual ReproductionSexual Reproduction

Most areMost are monoecious (both male andmonoecious (both male andfemale sex cells in one body)female sex cells in one body)

In some Demospongiae and CalcareaIn some Demospongiae and Calcarea Gametes develop fromGametes develop from choanocyteschoanocytes Some gametes fromSome gametes from archaeocytesarchaeocytes

Most sponges areMost sponges are viviparousviviparous where zygotewhere zygoteis retained within parent and provided withis retained within parent and provided withnourishment until it is released as anourishment until it is released as aciliated larvaciliated larva

OneOne sponge releases sperm which entersponge releases sperm which enterthe pores of another spongethe pores of another sponge

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Phylum PoriferaPhylum Porifera Different types of fertilization and zygoteDifferent types of fertilization and zygote

formation exits in spongesformation exits in sponges ViviparousViviparous sponges have choanocytessponges have choanocytes thatthat

phagocytize the sperm and transform intophagocytize the sperm and transform intocarrier cellscarrier cells that transport sperm through thethat transport sperm through themesohyl and to oocytes to form zygotesmesohyl and to oocytes to form zygotes

OviparousOviparous sponges release both sperm andsponges release both sperm andoocytes into water for external fertilizationoocytes into water for external fertilization

TheThe freefree--swimming larvaswimming larva of most spongesof most spongesis a solidis a solid--bodiedbodied parenchymula; six otherparenchymula; six otherlarval forms exits.larval forms exits.

The outwardly directed flagellated cells ofThe outwardly directed flagellated cells ofthe parenchymula becomethe parenchymula become choanocyteschoanocytes

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Phylum PoriferaPhylum Porifera Unique development patterns in CalcareaUnique development patterns in Calcarea

and some Demospongiaeand some Demospongiae HollowHollow stomoblastulastomoblastula develops with flagellateddevelops with flagellated

cells oriented toward the interiorcells oriented toward the interior Blastula then turns inside out (Blastula then turns inside out (inversioninversion) and the) and the

flagellated cells now turn outsideflagellated cells now turn outside Small flagellated cells orSmall flagellated cells or micromeresmicromeres located atlocated at

anterior end while larger nonanterior end while larger non--flagellatedflagellatedmacromeresmacromeres located at posterior endlocated at posterior end

MacromeresMacromeres overgrow invaginating micromeresovergrow invaginating micromeresduring metamorphosis and settlementduring metamorphosis and settlement

MicromeresMicromeres become choanocytes, archaeocytes,become choanocytes, archaeocytes,and collencytesand collencytes whilewhile macromeresmacromeres give rise togive rise topinacoderm and sclerocytespinacoderm and sclerocytes

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Figure 12.12 A) Development of demosponges, B) Development of thecalcareous syconoid sponge Sycon sp..

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Phylum PoriferaPhylum Porifera Class Calcarea (Calcispongiae)Class Calcarea (Calcispongiae)

Calcareous sponges with spicules ofCalcareous sponges with spicules ofcalcium carbonatecalcium carbonate

SpiculesSpicules are straight (monaxons) or haveare straight (monaxons) or havethree or four raysthree or four rays

Most are small with tubular or vase shapesMost are small with tubular or vase shapes Many are drab in color, but some are brightMany are drab in color, but some are bright

yellow, green, red, or lavenderyellow, green, red, or lavender Leucosolenia sp.Leucosolenia sp. andand Sycon sp.Sycon sp. are marineare marine

shallowshallow--waterwater Asconoid, syconoid and leuconoidAsconoid, syconoid and leuconoid bodybody

formsforms

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Figure 12.13 Some sponge body forms.

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Phylum PoriferaPhylum Porifera

Class Hexactinellida (Hyalospongiae)Class Hexactinellida (Hyalospongiae) Glass sponges with sixGlass sponges with six--rayed spicules ofrayed spicules of

silica bound together to form networksilica bound together to form network Nearly all areNearly all are deepdeep--seasea formsforms Most are radially symmetrical with vase orMost are radially symmetrical with vase or

funnel shaped bodies attached by stalks offunnel shaped bodies attached by stalks ofroot spicules onto the substrateroot spicules onto the substrate

HaveHave syncytialsyncytial cell structure that have manycell structure that have manynuclei with a large cell which were producednuclei with a large cell which were producedby the fusion of many cells or division ofby the fusion of many cells or division ofnuclei without dividing the cytoplasmnuclei without dividing the cytoplasm

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Phylum PoriferaPhylum Porifera Most Hexactinellids haveMost Hexactinellids have trabeculartrabecular

reticulumreticulum that isthat is bilayeredbilayered, sheet, sheet--like andlike andtubular with collagenous mesohyl cellstubular with collagenous mesohyl cells Cytoplasmic bridges connect choanoblastsCytoplasmic bridges connect choanoblasts

and archaeocytes with trabecular reticulumand archaeocytes with trabecular reticulum ChoanoblastsChoanoblasts are unusual cells that makeare unusual cells that make

flagellated outgrowths calledflagellated outgrowths called collar bodiescollar bodieswhose flagella beat to move water likewhose flagella beat to move water likechoanocyteschoanocytes

Food is collected by directing waterFood is collected by directing waterthrough the primary and secondarythrough the primary and secondaryreticulum layersreticulum layers

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Figure 12.14 Diagram of part of a flagellated chamber of hexactinellids.

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Phylum PoriferaPhylum Porifera Class DemospongiaeClass Demospongiae

ContainsContains 95% of living sponge species95% of living sponge speciesinclude most large spongesinclude most large sponges

SpiculesSpicules are siliceous but not six rayedare siliceous but not six rayedand may be absent or bound together byand may be absent or bound together bysponginspongin

LeuconoidLeuconoid body form for all speciesbody form for all species All marine except forAll marine except for Spongillidae,Spongillidae, thethe

freshwater spongesfreshwater sponges Marine demospongesMarine demosponges are highlyare highly varied invaried in

color andcolor and shape, with some growing toshape, with some growing toseveral meters in diameter.several meters in diameter.

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Phylum PoriferaPhylum Porifera

FreshwaterFreshwater demospongesdemosponges Widely distributed in wellWidely distributed in well--oxygenated pondsoxygenated ponds

andand streamsstreams They encrust plant stems and submergedThey encrust plant stems and submerged

woodwood Look like wrinkled scum, pitted and porousLook like wrinkled scum, pitted and porous

with brown and green colorswith brown and green colors Flourish inFlourish in summersummer andand inin early autumnearly autumn Reproduce sexually, but existing genotypesReproduce sexually, but existing genotypes

may also reappear annually frommay also reappear annually from gemmulesgemmules SpongesSponges die by late autumndie by late autumn and asexuallyand asexually

release gemmules to prepare for next yearsrelease gemmules to prepare for next yearspopulation.population.

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Figure 12.15 Marine Demospongiae on Caribbean coral reefs. A)Pseudoceratina crassa, B) Aplysina fistularis, C) Monanchora unguifera

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Phylum PoriferaPhylum Porifera Class HomoscleromorphaClass Homoscleromorpha

Mostly marine with a variety of colors butMostly marine with a variety of colors butlive in cryptic habitatslive in cryptic habitats

Generally found near shore but have deepGenerally found near shore but have deepwater formswater forms

Separated from Demospongiae due toSeparated from Demospongiae due topresence ofpresence of true basement membranetrue basement membraneunder pinacoderm or extracellular matrixunder pinacoderm or extracellular matrix

Also haveAlso have adherens cell junctionsadherens cell junctions thatthatfromfrom true tissuestrue tissues unlike other spongesunlike other sponges

Divided into two clades based on absenceDivided into two clades based on absenceor presence of spiculesor presence of spicules12-53

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Phylum PoriferaPhylum Porifera Phylogeny and Adaptive DiversificationPhylogeny and Adaptive Diversification

Sponges appeared before the Cambrian andSponges appeared before the Cambrian andtwo calcareous spongetwo calcareous sponge--like organisms werelike organisms werein Paleozoic reefs.in Paleozoic reefs.

Sponges share many traits with otherSponges share many traits with otheranimals and are considered sister taxonanimals and are considered sister taxon Proteins for cellProteins for cell adhesion and celladhesion and cell--signalingsignaling areare

homologous to other animalshomologous to other animals Some sponges haveSome sponges have basement membranebasement membrane withwith

collagen and adherens junctions with cadherincollagen and adherens junctions with cadherinmolecules that connect epithelial cellsmolecules that connect epithelial cells

Sponge haveSponge have blastulablastula and some formand some form gastrulagastrulastages like many animalsstages like many animals

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Phylum PoriferaPhylum Porifera Adaptive DiversificationAdaptive Diversification

Poriferans are a highly successful groupPoriferans are a highly successful groupwith thousands of species in diversewith thousands of species in diversehabitatshabitats

Diversification centers on theirDiversification centers on their uniqueuniquewaterwater--current systemcurrent system and its degree ofand its degree ofcomplexitycomplexity

New feeding modeNew feeding mode has evolved forhas evolved for spongesspongesfound infound in deep water caves with lowdeep water caves with lownutrientsnutrients

Illustrates the nonIllustrates the non--directional nature ofdirectional nature ofevolutionevolution

Phylum PoriferaPhylum Porifera Unique features of deep water spongesUnique features of deep water sponges

Many tinyMany tiny hookhook--like spicules coverlike spicules cover highlyhighlybranched bodybranched body

SpiculeSpicule layer can entangle the legs oflayer can entangle the legs ofcrustaceans that come near spongecrustaceans that come near sponge

Filaments of the sponge body grow overFilaments of the sponge body grow over prey,prey,slowly enveloping it and later digesting itslowly enveloping it and later digesting it

Most of the group are carnivores andMost of the group are carnivores and notnotsuspensionsuspension feedersfeeders

Some have symbiotic methanotrophicSome have symbiotic methanotrophicbacteriabacteria

Contain siliceous spicules, butContain siliceous spicules, but lacklackchoanocytes and internalchoanocytes and internal canals so verycanals so verydifferent than regular spongesdifferent than regular sponges12-56

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Figure 12.16 The carnivorous sponge, Chondrocladia lyra , iscommonly called a harp sponge.

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Phylum PlacozoaPhylum Placozoa Proposed by KProposed by K. G. Grell (1971). G. Grell (1971) based onbased on

a single speciesa single species-- Trichoplax adhaerensTrichoplax adhaerens Tiny (2Tiny (2--3 mm) marine form that is plate3 mm) marine form that is plate--likelike

and has no symmetryand has no symmetry No major organs, no muscular or nervousNo major organs, no muscular or nervous

systemsystem Lacks basal laminaLacks basal lamina beneath epidermis andbeneath epidermis and

no extracellular matrix but has genes for itno extracellular matrix but has genes for it Body has dorsal epithelium to cover cellsBody has dorsal epithelium to cover cells

and have thick ventral epithelium ofand have thick ventral epithelium ofmonociliated cells and nonciliated glandmonociliated cells and nonciliated glandcellscells

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Phylum PlacozoaPhylum Placozoa

Space between the epithelia containSpace between the epithelia containmultinucleated fibrousmultinucleated fibrous cells within acells within acontractilecontractile syncytiumsyncytium

PPlacozoans glides over food, secreteslacozoans glides over food, secretesdigestive enzymes, and absorb nutrientsdigestive enzymes, and absorb nutrients

Divide asexually and produce swarmerDivide asexually and produce swarmerstages by budding.stages by budding. No sexual stages have been seen but haveNo sexual stages have been seen but have

isolated eggs in the laboratoryisolated eggs in the laboratory ConsideredConsidered diploblasticdiploblastic with dorsalwith dorsal

epithelium representingepithelium representing ectodermectoderm andandventral epithelium representingventral epithelium representing endodermendoderm

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Figure 12.17 A) Trichoplax adhaerens is a marine placozoan, B)Section through Trichoplax adhaerens, showing histological structure.