Phylum Porifera

Sponges

Porifera

• Means pore bearing.

• Most simple of the multi-cellular organisms (Metazoans)

• Composed of a network of cells; no true tissues or organs

Porifera

• Cells are supported by a network of structures called spicules

• Silaceous: glass-like spicules

• Calcareous: calcium carbonate

• Spongin: elastic framework of protein fibers

Porifera

• Mostly marine, few freshwater

• Benthic: bottom dwelling

• Sessile: attached to the bottom, unable to move around.

• Found from the intertidal zone down to the depths of the ocean

• Found in tropical seas to cold polar waters

Life Functions

• Food particles, plankton and water flows in to the inner cavity through pores (ostia) which are surrounded by pore cells (porocytes)

• Water and wastes exit out through large opening at the top (osculum)

• Inside the sponge are colar cells (choanocytes) which have flagella and produce the current needed to move the water through the sponge.

Sponge Cells• Choanocytes also assist in capturing food particles• Amebocytes (archaeocyte): ingest and digest food

caught be choanocytes and transport them to the rest of the sponge. Totipotent cells (can change into other sponge cells).

• Sclerocytes: secretion of spicules• Spongocytes: secrete spongin• Pinocytes: outside layer of the sponge, tightly

packed• Between all the cells is a layer termed

mesenchyme.

Sexual Reproduction

• Most sponges are hermaphrodites; produce both egg and sperm but at different times.

• Broadcast Spawning: sponges release sperm into the ocean, eggs are retained in the sponge (internal fertilization)

• Early development takes place inside the sponge, tiny, flagellated larvae are released into the water.

• Larvae settle and attach to substrate and undergo an internal reorganization.

Asexual Reproduction

• Regeneration: whole body can be grown from parts of a parent body.

• Budding: new sponge grows from an older sponge and eventually breaks off.

• Gemmules: freshwater sponges; protective layer of spicules; protect sponge from desiccation, freezing, and low oxygen

Classes of Sponges

• Class Calcarea: spicules made of calcium carbonate

• Class Hexactinellida: spicules made of silica (form a lattice); glass sponges

• Class Demospongiae: largest class; contain spongin. Used commercially. Also contains the boring sponges that bore through shells of calcium carbonate.

Body Styles of Sponges

• Asconoids:

Size limitation, always small, most simple structure.

Body Style

• Syconoid: first stages of body wall folding

Body style

• Leuconoid: highest degree of folding, allows sponge to reach a large size. Majority of sponges are leuconoid.