Phylum Porifera Sponges Kingdom Animalia

Phylum Porifera – Pore Bearers Sponges have the lowest level of organization of all animals. They are at the cellular level of organization. –They are barely more than a colony of cells. –They are considered animals because they are multicellular, eukaryotic (have a nucleus), heterotrophs –They lack a nervous system, digestive system, and most other systems associated with animals

Sponges are found primarily in saltwater but some species can live in freshwater (over 10,000 species) Sponges are sessile (attached) filter feeders as adults. They can survive by moving the environment (which carries food and oxygen) through their bodies instead of moving through the environment. Sponges can reproduce sexually by releasing eggs and sperm into the water that would form a motile (moving) larvae that would find a hard substrate to attach to Sponges also reproduce asexually by budding, when a smaller sponge grows from the larger sponge, or a piece torn from the adult continues to grow on its own.

Sponge structure: –Epithelium (skin) protects the sponges outer surface –Collar cells (choanocytes) line the interior and use flagella to create the water current that flows into the sponge. Collar is covered in mucus and captures plankton as food. –Porocytes (pore cells) are imbedded in the skin and allow water to pass into the interior of the sponge –Amoebocytes are mobile cells found in the mesenchyme (jelly layer between the epithelium and the collar cells) that move around distributing nutrients and making the skeleton

–Skeleton Most sponges have a combination of spongin and spicules. The more spongin it has the softer it will be, the more spicules it has the harder it is. Spongin – tough fibrous flexible protein that give support to the sponge (this is what is left after the sponge is dead that humans use for various purposes, i.e. bathing) Spicules – needlelike structures that give the sponge support. Shape and composition of spicules are used to identify species of sponges. –Silica spicules (glass) –Calcareous spicules (limestone)