Kingdom: Animalia
Phylum: Porifera
General Characteristics
- Phylum Porifera includes sponges
- Sponges are simple multicellular animals that lack true tissues and organs, and are asymmetrical
- Larval sponges are free-swimming, adults are sessile, remaining attached to surfaces
- Several cell types have specialized functions
- Body is composed of different types of fibers - calcium carbonate, silica, or a protein called spongin
- Obtain nutrients by filter-feeding
Grantia (cross section)
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- Choanocytes (flagellated cells) pump water through the ostium (opening) of the incurrent canals
- Water circulates past the choanocytes in radial canals, which capture food particles
- The filtered water then flows out through the central opening of the sponge out the osculum
- The jelly-like mesohyl contains amoebocytes, spicules, and eggs
Scypha (cross section)
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- Note the repetitive folds in the walls of the sponge that increase surface area, allowing greater absorption of nutrients
Spicules (sponge fibers)
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- Small, needle-like fibers that make up the body structure of a sponge.
Spongilla (freshwater sponge) Gemmules
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- Gemmules are environmentally-resistant buds that contain amoebocytes surrounded by a thick layer of spicules. They allow the sponge to survive dessication and other hostile environmental conditions.