Porifera phylum

Porifera is a phylum of primitive invertebrate animals comprising the sponges and having a cellular grade of construction without true tissue or organ formation but with the body permeated by canals and chambers through which a current of water flows and passes in its course through one or more cavities lined with choanocytes.

2. Phylum Porifera
Poriferameans“pore-bearing”andreferstothenumerousporesand
channelsthatpermeateasponge’sbody.
Mostlymarine,butincludesomefreshwaterinhabitants;usuallyfound
attachedtothesubstratumorobjects-occasionallyonotheranimals
suchascrabsinshallowordeepwater.
Theyaresessile;permanentlyattachedtothesubstrate
Thereareapproximately9,000livingspeciesandabove2200fossil
forms.
Size–2metersto2cm
Saltwaterspongesarebrightlycoloredandfreshwaterspongesare
smallanddullgreencolor
someareround,flat,growascrustsorvase-like,tube-likeshape
someareradiallysymmetrical;mostareasymmetrical

3. General Morphology
•Thesurfaceofeachspongebearsminuteporescalledostia(ostium)or
incurrentpores.
•Theseporesleadintoacentralhollowcavity,theseinternalcavityiscalled
theparagastriccavityorspongocoel
•Itopenstooutsidethroughalargecircularopening,theosculum
•Waterisdrawnintoitthroughaseriesofincurrentporesordermalostia
presentinthebodywallintoacentralcavityandthenflowsoutofthesponge
throughalargeopeningatthetopcalledtheosculum.

4. Body Wall
The thin body wall which encloses the spongocoel, consists of two cellular
layers-
the outer pinacodermand
inner choanoderm
with a non-cellular mesenchyme in between.
Pinacoderm:
Itisanouterlayerofbody.
Thinandflatpolygonalcellsofpinacodermiscalledthepinacocytes
Itprotectstheinternalstructureofbody
Eachcellpresentsacentralbulgingcontaininganucleus
Marginsofadjacentcellsarecloselycementedtogether
Pinacocytesarehighlycontractile,sothatthespongecanincreaseor
decreaseslightlyinsize.

5. Therearespecial,largeandtubularcells,calledporecellsand
porocytes
Eachporocytecontainsacentralcanal-likespace,thesespaces
arecalledostiaordermalporesorincurrentpores.
Thesepermitwatertoflowfromoutsideintothespongocoel.
InSyconoidsponge,porocytesconnecttheincurrentcanals
withradialcanals
Throughtheirintracellularchannels,theprosopyles
Theopeningsofincurrentcanalsintooutsidearecalleddermal
ostiaandtheopeningsofradialcanalsintospongocoelarecalled
apopylesorinternalostia.

6. Sponge Anatomy
Pechenik, 1996
Pinacocyte
Choanocyte
Amoebocyte
Porocyte
Pinacoderm
Mesenchyme
Choanoderm

8. Choanoderm:
Itisaninnerlayerofbodywall
Asinglelayerofflagellatedcollarcellsof
choanoderm,arecalledchoanocytes
Achoanocyteisanovoidcellwithitsfreeend
bearingatransparentcontractilecollarwhich
surroundsasinglelongflagellumandanucleus
atthebaseorapexofitscell.
Choanocytesareusedinfeeding.Collarof
choanocytetrapsplankton(foodparticles)that
aresuspendedinthewater.
Choanocytesareusedinensuringtheflowof
waterwithintheanimal’sbodybybeatingtheir
flagella.
Thewatercurrenthelpingasexchange,
removalofwastes,andreleaseofthegametes

9. Mesenchyme:
Non-cellularmesenchymeispresentbetweenthepinacodermandthe
choanodermwhichissecretedbybothbodylayers
Itconsistsofagelatinousmatrixofproteincalledmesogloea;containsseveral
differentkindsoffreelywanderingamoeba-likecellscalledAmoebocytes
TheminuteskeletalelementsofmesenchymeisCaCo3whicharecalled
spicules
Archaeocytesareamoeboidcellsthatphagocytizefoodparticles;theycanalso
undergodifferentiationtoformothercells,includingcellsthatproducespicules
andgametes
Amoebocytes:
Theymaybedifferenttypesdependingupontheshapeoftheirpseudopodia
andfunction.
Thelarge-sizedprimaryamoebocyteswithbluntpseudopodiumandlarge
nucleusofthecelliscalledarchaeocytes
ThesecontainmuchRNAwhichcarryonallthefunctionsessentialforthelife
ofsponge.
Theyareself-replicatingandalsocapableofgivingrisetoallothertypesof
cells.Forthis,thesecellsarecalledtotipotent.

10. Theyalsogiverisetosexcellsandplayan
importantroleinregeneration
Thesecellsmaybedifferenttypes-
Scleroblasts:Theamoebocyteswhichmanufacture
theskeletonorspicules,arecalledasscleroblasts.
Accordingtothenatureoftheproductareknownas
calcoblasts,silicoblastsorspongioblasts
Collencytes:Mostoftheamoebocyteshave
branchingpseudopodiaoftenunitedintoanetwork
Chromocytes:Pigmentedamoebocyteswhichare
responsibleforthecolorofsponge
Thesocytes:Thoseamoebocyteswhichhave
roundedpseudopodiaandreservefoodmaterial.
Myocytes:Thoseamoebocyteswhicharepresent
aroundosculum.
Glandcells:Thoseamoebocyteswhichareattached
tothebodysurfacebylongstrandsandsecrete
slime

11. Sponge Anatomy
Pechenik, 1996
Pinacocyte
Choanocyte
Amoebocyte
Porocyte
Pinacoderm
Mesenchyme
Choanoderm

13. Skeleton
Theskeletoncomposedoftinypointedstructuresmadeof
silicaorcalciumcarbonatecalledspiculeswhichare
embeddedinmesenchyme
Skeletonmayalsomadeofnetworkofproteinfiberscalled
Spongin.
Theseendoskeletonprotectsandsupportsthesofterpartsof
thebody.
Calcareousspiculesarealllargespicules.

14. Types and structure of spicules

15. Development of spicules
Secretedby specialized
amoebocytes known as
scleroblasts
Amonaxonspiculeisformedby
twosclerocytesproducedbythe
divisionofonescleroblasts
Atriaxonspiculeisformedby
sixsclerocytesproducedbythe
divisionofthreescleroblasts
Founder cell
Thickener cell
scleroblast
sclerocytes

16. Water circulation
Thewatercurrentusedinfeeding,gasexchange,removalofwastes,and
releaseofthegametes
Becausethespongesaresessile
Watercurrentiscausedbyconstantbeatingofflagellaofchoanocytes
Bringsfoodandoxygenandremovesexcretoryandreproductiveelements
Course of water current:
Outside water OstiaIncurrent poreSpongocoelOsculumOutside

18. Food and feeding
Isafilterfeeder
Foodconsistsofplanktons(microscopicanimalsandplants)andorganic
particles.
Theygetfoodbycirculationofwaterwhichentersthroughtheostiatothe
spongocoel.
Openingsareconnectedbyaseriesofcanals,whicharelinedby
choanocytes(theflagellatedcollarcells)thatmaintainthecurrentandfilter
outfoodparticles.
Thechoanocyte’scollarconsistsofmicrovillijoinedtogetherbydelicate
microfibrils,whichfilterouttinyfoodparticles.
Thebeatingoftheflagellumdrawswaterthroughthecollarandoutthetop.
Particlestoobigtopassthroughthecollargettrappedinmucusandslide
downthecollartothebasewheretheyarephagocytized.
Somespongesalsosupplementtheirfilterfeedingbyhostingsymbionts
suchasgreenalgae,dinoflagellatesorcyanobacteriathatprovidenutrients
tothesponge.

19. Canal system
Insidethebodyofsponges,thewatercurrentflows
throughacertainsystemofspacescollectivelyforming
thecanalsystem
Mostspongeshaveoneofthreetypesofcanalsystem:
Ascontype
Sycontype
Leucontype
Thesesystemsdifferfromineachotherinthe
increasingcomplexity.

20. Ascontype
•Simplest type of canal system and found
only in asconoidsponges
•Its have one opening-ostiain its body wall
•The spongocoelis the large and flagellated
cavity
•It is lined by flagellated choanocytes
•Simplest organization,
•Small, branched and tube shaped,
e.g. Leucosolenia, Clathrinacanariensis,
Ingressingwater
Through
Ostia
spongocoel
Through
Osculum
To outside

21. Sycontype
Morecomplexcanalsystemandfoundonlyin
syconoidsponges
Derivedfromtheasconoidtypebyhorizontal
foldingofitswall
Havetwotypesofcanal-incurrentandradial,
parallelingandalternatingwitheachother
Incurrentcanalsarenon-flagellatedandradial
canalsareflagellated
havetwoopenings-dermalostiaandprosopyles
initsbodywall
Thespongocoelisthenarrowandnon-flagellated
cavity
Itislinedbypinacocytes
e.g. Scypha, Grantia
Ingressingwater
Dermal
Ostia
Incurrent
canals
Prosopyles
Radial
canals
Apopyles
Spongocoel
Osculum
Tooutside

22. Leucontype
•More complex canal system than sycon
type and found only in leuconoid
sponges
•Derived from the sycontype
•Flagellated chambers lined by
choanocytes
•All other spaces are lined by
pinacocytes
•incurrent canals open into Flagellated
cluster chambers through prosopyles
and opens into excurrentcanals
through apopyles
•Spongocoelis excessively narrow and
partly disappeared
e.g. Spongilla
Ingressingwater
Dermal
Ostia
Incurrent
canals
Prosopyles
Flagellated
chambers
Apopyles
Excurrent
canals
Osculum
To outside

23. Class Calcarea(calcareous sponges)
Smallinsizeandcylindricaland
vase-likeinshape
Onlyspongesthatpossess
spiculescomposedofcalcium
carbonate.
Spiculesarestraightorhave3-4
rays
allmarine,especiallyshallow
waters
Bodyorganizationofasconoid,
syconoidandleuconoidtype
e.g. Leucosolenia, Scypha
Classification

24. ClassHexactinellida(Hyalospongiae)
ModeratesizedGlasssponges;
Bodyshapecup,urnorvase-like
characterizedbysiliceousspicules
consistingofsixraysintersectingatright
angles
Nodermalepitheliumorex-pinacoderm
Exclusivelymarine,indeepsea
E.g.Euplectella(Venusflower)

25. ClassDemospongiae(Mostsponges)
•Greaterthan90percentofthe5,000
knownlivingspongespeciesare
demosponges.
•Smalltolarge-sizedandvase,cupor
cushionshapedbody
•Demosponge skeletonsare
composedofsponginfibersor
siliceousspiculesorboth
•Siliceousspiculeswithonetofour
raysnotatrightangles,
•Allmembersexpresstheleuconoid
bodyform
•Mostlyfoundonthecontinental
shelfinwelloxygenatedhabitats
•Allmarineexceptfreshwaterfamily
Spongillidae
e.g.Thenea,Spongilla
Yellow sponge growing on a wall
on a Caribbean reef.

26. Reproduction in Sponges
SEXUAL
•Spongesaremonoecious(hermaphrodite)anddioecious
species
•Spermandovaarederivedfromarcheocyteswhich
undergogametogenesis
•MainlyCross-fertilizationoccursbecausemostspongesare
hermaphroditeandproduceeggsandspermatdifferent
timessotheydonotselffertilize
•Spermsarereleasedtooutsidethroughwater.
•Choanocytesactingasnursecellswhichtransportthe
spermstotheova.
•Developmenttakesplacewithinthematernalsponge
•Twotypesoflarvae-
Amphiblastula-characteristicsofmanycalcareoussponges
Parenchymula-characteristicsofsomecalcareous,
HexactinellidaandmostDemospongiaesponges
Marine sponges
•Budding
•Fragmentation
•Regeneration
Freshwater
sponges
•Gemmules
•Budding
•Fragmentation
•Regeneration

28. Asexual:
Fragmentation:
Whenindividualpieces
ofspongethatarefree
floatinginthewater
columncometogether
toformasponge
themselves
Budding:
Spongescangrowbuds
thatbecomedetached
andformsponges
themselves
Gemmules:
Internalbudssurroundedby
sponginandspiculesthat
allowspongestosurvivein
harshconditions;whenparent
spongedies,gemmule
developsintoanewsponge
whenconditionsarefavorable

29. Branching Tube Sponge

30. Stove Pipe Sponge

31. Vase Sponges

32. Barrel Sponges

33. Ball Sponges

34. Rope
Sponges