Biology 320Biology 320Invertebrate ZoologyInvertebrate Zoology

Fall 2005Fall 2005

Chapter 5 – Phylum PoriferaChapter 5 – Phylum Porifera

Phylum PoriferaPhylum Porifera The spongesThe sponges

Name Porifera means “pore Name Porifera means “pore bearers”bearers”

First metazoan phylum we will First metazoan phylum we will discussdiscuss

Posses epithelioid and rudimentary Posses epithelioid and rudimentary connective tissueconnective tissue

Lack true muscle and nervous Lack true muscle and nervous tissuestissues

Not considered to be eumetazoansNot considered to be eumetazoans

Approximately 8000 spp. Approximately 8000 spp. of spongesof sponges

Mostly marine, with Mostly marine, with approx. 150 described approx. 150 described freshwater spp.freshwater spp.

Primitive, sessile filter Primitive, sessile filter feedersfeeders

Most are asymmetrical, Most are asymmetrical, but some display radial but some display radial symmetrysymmetry

Can be erect, branching, Can be erect, branching, or encrusting on or encrusting on substratumsubstratum

Body DesignBody Design

Three main forms of sponges, classified according Three main forms of sponges, classified according to complexityto complexity

AsconoidAsconoid SyconoidSyconoid LeuconoidLeuconoid

Asconoid spongesAsconoid sponges Simplest body planSimplest body plan Resemble a hollow tube, with the base attached to the substrateResemble a hollow tube, with the base attached to the substrate Possesses one large spongocoel lined with a single layer of Possesses one large spongocoel lined with a single layer of

choanodermchoanoderm Choanocytes beat and draw water through ostia in the epidermisChoanocytes beat and draw water through ostia in the epidermis

Asconoid sponges cont…Asconoid sponges cont… Water exits spongocoel through a Water exits spongocoel through a

single large osculumsingle large osculum

Smallest of all sponges (1mm in Smallest of all sponges (1mm in diameter)diameter)

Thinnest body wallsThinnest body walls

LeucosoleniaLeucosolenia

Growth is limited by spongocoel Growth is limited by spongocoel diameterdiameter

If asconoid sponges had larger If asconoid sponges had larger diameters, body volume would diameters, body volume would exceed pumping capacity of exceed pumping capacity of choanodermchoanoderm

Therefore, a only a change in this Therefore, a only a change in this simple body plan would permit the simple body plan would permit the evolution of larger body sizes in evolution of larger body sizes in spongessponges

Syconoid SpongesSyconoid Sponges Body wall contains pockets, Body wall contains pockets,

known as choanocyte chambers, known as choanocyte chambers, that are lined with choanodermthat are lined with choanoderm

Increases choanoderm surface Increases choanoderm surface areaarea

Decreases spongocoel volumeDecreases spongocoel volume

Larger than asconoid sponges Larger than asconoid sponges (one cm – a few cm)(one cm – a few cm)

Body walls are thicker than in Body walls are thicker than in asconoid spongesasconoid sponges

GrantiaGrantia and and SyconSycon (formerly (formerly ScyphaScypha))

Leuconoid spongesLeuconoid sponges

Contains thousands of Contains thousands of choanocyte chambers, choanocyte chambers, thereby further increasing thereby further increasing the choanoderm SAthe choanoderm SA

Spongocoel is further Spongocoel is further reducedreduced

Therefore, these are the Therefore, these are the largest sponges (few cm to largest sponges (few cm to one meter, or more)one meter, or more)

Thickest body wallsThickest body walls

May possess more than one May possess more than one osculumosculum

Body Wall CompositionBody Wall Composition The body walls of sponges are classified as either The body walls of sponges are classified as either

being cellular or syncytialbeing cellular or syncytial

Cellular sponges have two primitive Cellular sponges have two primitive primaryprimary tissuestissues Epithelioid – resembles epitheliumEpithelioid – resembles epithelium Mesohyl – connective tissue middle layerMesohyl – connective tissue middle layer

There are two There are two specificspecific types of epithelioid tissue types of epithelioid tissue Pinacoderm – lines inside (except where choanoderm is Pinacoderm – lines inside (except where choanoderm is

present) and outsidepresent) and outside Choanoderm – choanocytes posses a flagellum and Choanoderm – choanocytes posses a flagellum and

collar of microvillicollar of microvilli

Mesohyl is a fibrous (proteinaceous) ECM Mesohyl is a fibrous (proteinaceous) ECM containing cells and skeletal elementscontaining cells and skeletal elements

All mesohyl cells are totipotent and amoeboidAll mesohyl cells are totipotent and amoeboid Archeocytes – can differentiate into any type of Archeocytes – can differentiate into any type of

sponge cell. Aide in digestion (via phagocytosis) sponge cell. Aide in digestion (via phagocytosis) and internal transportand internal transport

Lophocytes – secrete and maintain collagen Lophocytes – secrete and maintain collagen fibersfibers

Spongocytes – responsible for producing thick Spongocytes – responsible for producing thick skeletal fibers known as sponginskeletal fibers known as spongin

Mesohyl cells cont…Mesohyl cells cont…

Sclerocytes – secrete Sclerocytes – secrete spicules, interesting spicules, interesting skeletal elements made of skeletal elements made of silica or calciumsilica or calcium

Myocytes – essentially Myocytes – essentially muscle cells; usually muscle cells; usually concentrated around concentrated around osculum. Constrict or osculum. Constrict or dilate to control water flowdilate to control water flow

Germ cells – reproductive Germ cells – reproductive cellscells

Syncytial sponges DO posses cells, but not at Syncytial sponges DO posses cells, but not at the same level of organization as cellular the same level of organization as cellular spongessponges

Cytoplasm is continuous and lacks membranes that Cytoplasm is continuous and lacks membranes that compartmentalize separate cellscompartmentalize separate cells

Lack pinacodermLack pinacoderm

Lack choanoderm. Posses collar bodies instead; Lack choanoderm. Posses collar bodies instead; these are located in collar body chambers, individually these are located in collar body chambers, individually rather than in epitheliod sheetsrather than in epitheliod sheets

Mesohyl is present and contains archeocytes, Mesohyl is present and contains archeocytes, sclerocytes, and germ cellssclerocytes, and germ cells

Syncytial sponges cont…Syncytial sponges cont… Body wall resembles a 3D cobweb-like pattern and is called a Body wall resembles a 3D cobweb-like pattern and is called a

trabecular syncytiumtrabecular syncytium

Each strand of the trabecular syncytium encloses an axis of Each strand of the trabecular syncytium encloses an axis of mesohylmesohyl

Collagen and spicules are presentCollagen and spicules are present

TaxonomyTaxonomy Two subphylaTwo subphyla

Subphylum Symplasma Subphylum Symplasma (Hexactinellida)(Hexactinellida)

Subphylum CellulariaSubphylum Cellularia

Subphylum Symplasma Subphylum Symplasma consists of glass sponges consists of glass sponges that posses syncytial tissuesthat posses syncytial tissues

Most sponges belong to Most sponges belong to Subphylum Cellularia, which Subphylum Cellularia, which is divided into two main is divided into two main classes, both possessing classes, both possessing cellular tissuescellular tissues

Class Demospongiae – have Class Demospongiae – have siliceous spicules and sponginsiliceous spicules and spongin

Class Calcarea – have Class Calcarea – have calcareous spiculescalcareous spicules

SkeletonSkeleton Any cell, organism, etc. needs Any cell, organism, etc. needs

some form of supportsome form of support

Mesohyl acts as an Mesohyl acts as an endoskeletonendoskeleton

Diversity of mesohylar structureDiversity of mesohylar structure Fine collagen fibers onlyFine collagen fibers only

May be supplemented with spicules, May be supplemented with spicules, spongin, or bothspongin, or both

Incredible diversity of spicules; and Incredible diversity of spicules; and some can project through mesohyl some can project through mesohyl to protect the outside of the spongeto protect the outside of the sponge

Water PumpingWater Pumping

Most pump a volume of Most pump a volume of water equal to their body water equal to their body volume, every 5 secondsvolume, every 5 seconds

Can slow / stop water flow Can slow / stop water flow to avoid taking in siltto avoid taking in silt

Can control rate of water Can control rate of water flow viaflow via

Contracting or relaxing Contracting or relaxing myocytes, which controls myocytes, which controls osculum diameterosculum diameter

Closing ostiaClosing ostia

Adjusting flagellar beat of Adjusting flagellar beat of choanoderm / collar bodieschoanoderm / collar bodies

LocomotionLocomotion

Some have limited Some have limited capacity for locomotioncapacity for locomotion

Can move 1 to 4 mm per Can move 1 to 4 mm per dayday

Result of collected Result of collected amoeboid movement of amoeboid movement of cellscells

Osculum contractionOsculum contraction

Whole body contractionWhole body contraction

NutritionNutrition Filter feedersFilter feeders

Typically phagocytize Typically phagocytize particles of 50µm or lessparticles of 50µm or less

Particle size determines Particle size determines which cells phagocytizewhich cells phagocytize

All cells can phagocytizeAll cells can phagocytize

Choanocytes transfer Choanocytes transfer particles to vacuoles for particles to vacuoles for digestiondigestion

Archeocytes remove Archeocytes remove wastes / inorganics from wastes / inorganics from systemsystem

Feed on dinoflagellates, bacteria, viruses, debris, etc.Feed on dinoflagellates, bacteria, viruses, debris, etc.

Some are carnivorous (don’t filter); trap small animals such Some are carnivorous (don’t filter); trap small animals such as crustaceansas crustaceans

May posses photosynthetic May posses photosynthetic endosymbiontsendosymbionts

CyanobacteriaCyanobacteria DinoflagellatesDinoflagellates ChlorophytesChlorophytes

Symbionts may cause Symbionts may cause sponge to be brightly sponge to be brightly coloredcolored

Sponges must live in Sponges must live in shallow water to shallow water to photosynthesizephotosynthesize

Some obtain up to 80% of Some obtain up to 80% of nutrients from nutrients from photosynthatephotosynthate

Internal TransportInternal Transport Gas / waste transport is carried out via simple diffusionGas / waste transport is carried out via simple diffusion

Sponges are “leaky,” so water penetrates almost the entire Sponges are “leaky,” so water penetrates almost the entire animalanimal

Sheets of cells are only one cell layer thickSheets of cells are only one cell layer thick Mobile amoeboid cellsMobile amoeboid cells

Ammonia is the main metabolic wasteAmmonia is the main metabolic waste Almost always the case for animals in aqueous environmentsAlmost always the case for animals in aqueous environments Uric acid or urea in terrestrial habitatsUric acid or urea in terrestrial habitats

Archeocytes transfer wastes / nutrientsArcheocytes transfer wastes / nutrients

Some individual cells posses contractile vacuolesSome individual cells posses contractile vacuoles

Nervous TissueNervous Tissue

Lack nerve cellsLack nerve cells

Some have localized Some have localized impulses responsible for impulses responsible for myocyte contractionmyocyte contraction

Glass sponges can generate Glass sponges can generate action potentials that travel action potentials that travel all across their syncytium at all across their syncytium at a rapid ratea rapid rate

Used to arrest flagellar beatingUsed to arrest flagellar beating

EcologyEcology Many produce toxins to Many produce toxins to

prevent predationprevent predation

Some animals are Some animals are spongivoresspongivores

Nudibranchs Nudibranchs FishFish Turtles – Hawksbill turtle feces Turtles – Hawksbill turtle feces

can be up to 95% siliceous can be up to 95% siliceous spiculesspicules

Some release chemicals Some release chemicals that kill competing sessile that kill competing sessile organisms, such as corals organisms, such as corals

Some animals such as Some animals such as shrimps and brittle stars shrimps and brittle stars live in spongeslive in sponges

Decorator crabs may Decorator crabs may place sponges on their place sponges on their carapacescarapaces

ClionaCliona breaks down breaks down calcareous shells. Bores calcareous shells. Bores into shells for protectioninto shells for protection

ReproductionReproduction Sponges are excellent regeneratorsSponges are excellent regenerators

Reproduce clonally through several methodsReproduce clonally through several methods Fragmentation – usually due to wave damage or Fragmentation – usually due to wave damage or

grazinggrazing

BuddingBudding

Gemmules (winter bodies) – spore-like structures that Gemmules (winter bodies) – spore-like structures that are essentially a mass of nutrient-laden archeocytes are essentially a mass of nutrient-laden archeocytes that are surrounded by a shell. Undergo diapause that are surrounded by a shell. Undergo diapause

Sponges frequently Sponges frequently reproduce sexuallyreproduce sexually

Sponges are Sponges are hermaphrodites hermaphrodites (monoecious)(monoecious)

Germ cells occur Germ cells occur throughout mesohyl throughout mesohyl Choanocytes can Choanocytes can

also release sperm, also release sperm, and form eggsand form eggs

Sperm are broadcasted Sperm are broadcasted into water columninto water column

Choanocytes phagocytize Choanocytes phagocytize incoming sperm, but don’t incoming sperm, but don’t digestdigest

They differentiate into an They differentiate into an amoeboid cell and deliver amoeboid cell and deliver sperm head to eggsperm head to egg

Most eggs are fertilized Most eggs are fertilized through phagocytosis through phagocytosis (therefore, most sponge (therefore, most sponge sperm lack an acrosome)sperm lack an acrosome)

Some sponges are oviparous, and release zygotes into water columnSome sponges are oviparous, and release zygotes into water column

Most are viviparous, and retain zygotes in their body, later releasing Most are viviparous, and retain zygotes in their body, later releasing larvaelarvae

Sponge larvae are very diverseSponge larvae are very diverse

Larvae are short livedLarvae are short lived Settle within a few daysSettle within a few days

Creep across substrate until a Creep across substrate until a suitable spot is foundsuitable spot is found

Metamorphose into a juvenileMetamorphose into a juvenile

Varied lifespansVaried lifespans May live one to a few years in May live one to a few years in

temperate zonestemperate zones

Tropical or deep sea spp. May live Tropical or deep sea spp. May live 200 years or more200 years or more

Some only grow 0.2 mm/yr, and Some only grow 0.2 mm/yr, and could be 5000 years old if that could be 5000 years old if that growth rate is constantgrowth rate is constant