Phylum Porifera

SpongesAncient group of animals that dates

back to the late Precambrian about 600 million years ago

Phylum Porifera (sponges)

• Sessile, aquatic, benthic, suspension feeders on bacteria and protists

• Mainly marine (~7000 species), but some in freshwater (~300 species).

• ~27 freshwater species in North America.

Phylum Porifera

• Filter feeders (a few are carnivorous)– Water current produced by choanoflagellates delivers

particles and dissolved organic material to all the cells

– Food enters cells by• Phagocytosis (particles)

• Pinocytosis (dissolved organic materials)

– Digestion is intracellular

• Wastes are eliminated by diffusion

• Gas exchange is by diffusion

Defining Characteristic of Phylum

• Cellular level of organization– No true tissues– Cells are not connected to each other by basement

membrane as seen in true tissues

• Cells are totipotent– Can change form and function

• No true embryological germ layers– 3 types of embryological germ layers in animals

• Ectoderm• Endoderm• Mesoderm

Not all animal phyla have all 3 layers

Defining Characteristic of Phylum

• Body covered in holes (ostia)– Pores - hence the name Porifera

• “Pore bearer”– Skeleton made of spicules

• Silica

• CaCO3

• Spongin – organic material

• No fixed body shape• No plane of symmetry

– Some have radial symmetry

Defining Characteristic of Phylum

• Adults are sessile (immobile)

• Suspension feeders

• Flagellated cells called choanocytes circulate water through canal system

• No nerves or muscles

• Larvae are flagellated and free swimming

Defining Characteristic of Phylum

• Microvillae form collars around flagella of Collar cells = Choanocytes

• Functions of choanocytes– Generate currents that

maintain water flow throughout sponge.

– Capture small food particles.– Capture sperm for

fertilization.

nucleus

microvillus

Flagellum

Collar

Sponge Cells • Pinacocytes – form the pinacoderm, the outermost layer of

sponge

• Choanocytes – flagellated collar cells that pump water through the sponge, form the choanoderm

• Amoebocytes (or Archaeocytes) are amoeba-like cells that are totipotent, in other words each is capable of transformation into any other type of cell. They also have important roles in feeding, reproduction and in clearing debris that blocks the ostia. Amoebocytes wander through the central jelly or mesohyle

• Porocytes – line the pores (or ostia) of the sponge; provide channels to spongocoel

Pinacocytes (“tablet cells”) form outer epithelium

Choanocytes circulate water, capture prey, capture sperm

Amoebocytes or archaeocytes Wander through mesohyl;can become other cell types, form gametes, help in feeding, clear debris from ostia

Amoebocytes

Porocytes (pore cells)provide channels to spongocoel

Mesohyl

• Middle layer of sponge

• Acellular matrix– Gelatinous

– Nonliving

– Acellular

• Contains archaeocytes

• Contains spicules and spongin

Osculum

spongocoel(atrium)

Generalized Sponge Anatomy

inhalant pore (ostium)

Pinacoderm made of pinacocytes

Ostia lined by porocytes

Mesohyle with amoebocytes

Choanoderm with choanocytes

Cell Layers

Other types of cells within the mesohyl

• Sclerocytes secrete the mineralized spicules ("little spines") that form the skeletons of many sponges and in some species provide some defense against predators.

• Spongocytes secrete spongin.

• Lophocytes are amoeba-like cells that move slowly through the mesohyl and secrete collagen fibres.

• Collenocytes are another type of collagen-producing cell.

• Rhabdiferous cells secrete polysaccharides that also form part of the mesohyl.

Other types of cells within the mesohyl

• In addition to or instead of sclerocytes, demosponges have spongocytes that secrete a form of collagen that polymerizes into spongin, a thick fibrous material that stiffens the mesohyl.

• No specialized communication cells. Cells signal each other by

DIFFUSION of chemical messages • Myocytes ("muscle cells") regulate the opening and closing of

the porocytes . • "Grey cells" act as the equivalent of an immune system for the

sponge.

• Oocytes and spermatocytes are reproductive cells.

Sponge Skeletal MaterialsSponge Skeletal Materials

• SpiculesSpicules and and sponginspongin fibers are fibers are– StructuralStructural– Used in defense against predatorsUsed in defense against predators

• Also important for identification of spongesAlso important for identification of sponges

Sclerocytes - derived from amoebocytes; produce spicules

Growth of a sponge spiculeGrowth of a sponge spicule Growth of a sponge spiculeGrowth of a sponge spicule

Spicule

Founder cell

Thickener cell

Sclerocytes - derived from amoebocytes; produce spicules

Additional spicule shapes

Massive calcium carbonate supports evolved several times independently in the Demospongiae and the Calcarea.

Sponge Body Plans

• Asconoid

• Syconoid

• Leuconoid

• See handout for details of water flow and anatomy– for practice, label the following diagrams

   

Choanocytes Mesohyl Water flow

   

Asconoid Syconoid Leuconoid

   

Pinacocytes

Leucosolenia

Asconoid sponge

Leucosolenia

Asconoid Body Plan

Simplest body type

Found only in the Calcarea

Choanoderm is simple and continuous

Water:

• enters through pores

• and flows into spongocoel

• then out through osculum.

Spicule

Pinacoderm

Porocyte

Osculum

Spongocoel

Mesohyl

Amoebocyte

Choanocyte in choanoderm

Inhalant pore

Structure and organization of Structure and organization of an an asconoidasconoid sponge. sponge.

Structure and organization of Structure and organization of an an asconoidasconoid sponge. sponge.

Grantia = Scypha = Sycon

See following slides for anatomy

Grantia = Scypha = Sycon

Syconoid Body PlanMore complex body type

Choanoderm is folded into many radial canals

Water:• enters through pores• and travels through radial

canals to spongocoel• then out through osculum.

Structure and organization of Structure and organization of a a syconoidsyconoid sponge. sponge.

Structure and organization of Structure and organization of a a syconoidsyconoid sponge. sponge.

Spongocoel

Pinacoderm

Choanocyte

Mesohyl

Amoebocyte

Osculum

Spicule

Radial Canal

Incurrent Pore

Incurrent Canal

Internal water canal

Grantia longitudinal section; water flow shown by arrows

apopyle

http://faculty.shc.edu/cchester/BIO205/Labs/Lab%2003/sycon400.htm

Grantia cross section; water flow shown by arrows.

Grantia

details of radial canal

Structure and organization of a Structure and organization of a leuconoidleuconoid sponge sponge

Leuconoid Body PlanMost common and most complex type of sponge body

Water:• flows in through pores into

inhalant canals. • It then enters choanocyte

lined chambers… • …and finally travels the

excurrent canals to the osculum.

Detailed organization of the leuconoid sponge

Prosopyle

Apopyle

HexactinellidaHexactinellida

Glass sponge community in Antarctica's Glass sponge community in Antarctica's eastern Weddell Sea, in an area not eastern Weddell Sea, in an area not

covered by ice shelves covered by ice shelves

• Major component of the body is the trabecular syncytium.• Flagellated cells lack nuclei, and are called collar bodies.  • Produced by nucleated choanoblasts.

Trabecular Syncytium

• Is the largest example of a syncytium known in the animal kingdom.

• Comes from fusion of early embryonic cells.• Embryos are cellular until gastrulation

• SO - Hexactinellid sponges may have evolved from cellular sponges

• Syncytium– Is Cytoplasmic– Lacks cell walls– Possesses multiple nuclei– Is bilayered – Extends through the

entire body of the sponge.

• Syncytium– Connects through

cytoplasmic bridges to various cells in the sponge, such as choanocytes and archaeocytes.

http://www.mareco.org/khoyatan/spongegardens/diagram1a.gif

Trabecular Syncytium

• Primary reticulum, encloses and supports the collar bodies and the choanoblasts

• Secondary reticulum, branches from the primary reticulum and forms a kind of barrier around the collars of the collar bodies. 

• Nuclei are scattered within the two reticula. • Water is drawn through openings, or prosopyles, and

moves through the microvilli of the collar bodies then through the excurrent canals to the outside through apopyles.

• Some water passes directly through the prosopyles into the flagellated chamber

prosopopyle

blast

Trabecular Syncytium

• Cytoplasm within the syncytium flows bidirectionally.

• Food products may be distributed through the sponge via the syncytium and not via cellular transport as in other sponges.

Classification

• 2 subphyla– Symplasma– Cellularia

• 4 Classes based on type of spicules– Hexactinellida– Calcarea– Demospongiae– Homoscleromorpha

Classification

• Based on type of skeleton– Class Hexactinellida

• Spicules made of silica (glass)• Maybe should be separate phylum

– Class Calcarea• Spicules made of calcium carbonate

– Class Demospongiae• Siliceous spicules in some• Spongin fibers only in some• Both spicules and spongin fibers• One family lacks a skeleton entirely

Classification

• Subphylum: Symplasma– Class: Hexactinellida

• Acellular syncitium– Trabecular syncitium (discussed later)

• Spicules made of silica (glass sponges)

Hexactinellida

= Hexactinellida

Hexactinellida

• Live in deep water

• Habitat favored possibly because body structures are so fragile.

Euplectella Euplectella Venus’ Flower Venus’ Flower Basket SpongeBasket Sponge

A deep water species. Often A deep water species. Often contains a pair of shrimp that contains a pair of shrimp that entered as juveniles and remain entered as juveniles and remain trapped inside their entire lives. trapped inside their entire lives. Usually many small shrimp Usually many small shrimp arrive and the first pair to arrive and the first pair to achieve sexual maturity kill off achieve sexual maturity kill off the rest. Often given to the rest. Often given to Japanese couples as a wedding Japanese couples as a wedding present symbolizing fidelity and present symbolizing fidelity and long life together.long life together.

Hmmmmmm – prisoners and Hmmmmmm – prisoners and murderers?murderers?

SpongicoloidesSpongicoloides

Spongicoloides

• Unusual eyes. – In contrast to the sensitive optics used in the eyes

of almost all other adult decapod shrimps, spongicolids retain the less sensitive optics used by larval decapods. (We’ll talk about this later with discussion of arthropods.)

– These eyes are derived by neoteny, possibly reflecting the limited value of more specialised eyes within the body cavity of the sponge at depths of 100 – 1500 m.

SpongillaSpongilla

Freshwater Freshwater SpongeSponge

HexactinellidaeHexactinellidae

Freshwater sponges are useful for Freshwater sponges are useful for monitoring pollution. In addition, they monitoring pollution. In addition, they produce an antibiotic that may have produce an antibiotic that may have important biomedical and ecological important biomedical and ecological functions.functions.

Read article on East Chicago Sanitary Read article on East Chicago Sanitary District Wastewater Treatment Plant – District Wastewater Treatment Plant – sponges and salmonsponges and salmon

http://www.chicagowildernessmag.org/issues/fall2007/sponges.html

Watch the video!Watch the video!

HexactinellidaSpicules: 6-sided

Siliceous spicules

Electron micrograph

Yellow Picasso sponges (Staurocalyptus sp.)

Siliceous spicules

Ernst Haeckel

Siliceous Spicules

Classification

• Subphylum: Cellularia– Class: Calcarea

• Spicules made of calcium carbonate

SP Cellularia(Class Calcarea)Clathrina canariensis

SP Cellularia(Class Calcarea)

Classification

• Subphylum: Cellularia– Class Demospongiae

• Siliceous spicules• Spongin fibers only• Both spicules and spongin fibers• One family lacks a skeleton entirely

Spongin fibers

SP Cellularia SP Cellularia (Class (Class Homoscleromorpha)Homoscleromorpha)

Classification

• Subphylum: Cellularia– Class: Homoscleromorpha (newly separated

from Demospongiae)• Very simple structure- once considered to be

“primitive” sponges

Homoscleromorpha

– Reduced skeletons; some lack spicules entirely

– Spicules are all the same (homoschleromorpha)

– Spicules are siliceous

– Spicules tend to be very small, don’t form a well-organized skeleton. 

Classification

• Subphylum: Cellularia– Class: Homoscleromorpha (newly

separated from Demospongiae)

• Small group (<100 described species in 2 families) of exclusively marine sponges

• Generally located in shallow waters from 8 to 60 m, but also at more than 1000 m depth

• Dwellers of hard substrate communities often in semi-dark or dark caves 

Homoscleromorpha

• Reproduction is viviparous

• Larva = amphiblastula. 

• Suspension feeders

• Chemical defense producers

• Builders of substrate

• Bioeroders of calcareous concretions

Homoscleromorpha

• Characters shared with Eumetazoa– True epithelium: basement membrane

with collagen – zonula adhaerens cell junctions– Acrosomes in sperm

• Character shared with calcareous sponges– Cross-striated rootlets in the flagellar

basal apparatus of larval cells– (Also found in at least one

demosponge)

(f) Oscarella viridis TEM micrograph showing basement membrane (arrow heads)

(h) Plakina trilopha TEM micrograph of the cross-striated ciliary rootlet

(i) Oscarella microlobata TEM micrograph of cell junctions (zonula adhaerens)