Phylum Porifera (sponges)


No symmetry (asymmetry)
No Tissues
No Organs



Sexually- amoebocytes differentiate into egg cells or sperm cells
They are fertilized to produce a zygote
The cell divides by mitosis
Becomes a hollow sphere called a blastula
Mobile Laval Stage
Then it grows flagellum and us an amphiblastula stage
Through metamorphosis settles down
The flagellum develop in to collar cells
hermaphrodite - an animal in which each adult can act as either the female or the male in reproduction


Asexually- amoebocytes make a cluster
Then secrete spicules
Then priduce a protein coat
Producing a gemmule

Slide 48 gemmules - with spicules

slide 47 spicules

Types Catorgorized based on spicules

Calcarea (calcerous sponges - having spicules made of protien)
Demospongiae (horn sponges, like the bath sponge spicules made of protein)
Scleropongiae (coralline or tropical reef sponges spicules made of Calcium carbonate CaCO)
Hexactinellida (glass sponges spicules made of silica)


archaeocytes (amoebocytes)
Cells with pseudopods, located in the mesohyl.
used in processing food, distributing it to other cells, and for other functions.

choanocyte - also called collar cells, choanocytes line the inner cavity of the sponge.
have a sticky, funnel-shaped collar (that collects food particles)
flagellum (which whips around, moving water).
obtains sponge’s nutrients and oxygen by processing flowing water using choanocytes.
also involved in sponge reproduction; they catch floating sperm

epidermis (pinacocyte)
layer of cells that covers the outer surface of the sponge
The thin, flattened cells of the epidermis are called pinacocytes.

flagellum whip-like structure of a choanocyte;
the flagellum moves, pushing water (which contains nourishment) through the sponge.
holdfast root-like tendrils that attach the sponge to rocks.

mesohyl (mesenchyme) the gelatinous layer between the outer body of the sponge and the spongocoel (the inner cavity).

osculum - a large opening in a sponge through which water flows out of the sponge.Sponges may have more than one oscula.

ostia - a series of tiny pores all over the body of a sponge that let water into the sponge. One of these is called an ostium.

pinacocyte - pinacocytes are the thin, flattened cells of the epidermis, the sponge's outer layer of cells.

porocyte - cells with pores that allow water into the sponge; they are located all over the sponge's body.=

sessile - permanently attached to a substrate and unable to move on its own. Adult sponges are sessile.

spicule - spicules are sharp spikes (made of calcium carbonate) located in the mesohyl. Spicules form the "skeleton" of many sponges.

spongin - the flexible, fibrous fibers that form the skeleton of horny sponges; spongin is located within the mesohyl.

spongocoel - the central, open cavity in a sponge through which water flows.

water flows into the sponge - water flows into a sponge through cells with pores (these cells are called porocytes) located all over its body.

water flows out of the sponge - water flows out of a sponge through large openings called oscula (plural). Each of these large openings is called an osculum.

Learn More from Wikipedia

Lab Slides

Slide 28 Leucoslenia

mesohyl is stained, spicules are not because they are made of silica

Slide 27 28

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