Parazoa: The Sponges
Phylum Porifera: Sponges, only animals that lack tissues; mass of cells embedded in gelatinous matrix
5000 species, 150 in freshwater
Size: from few millimeters to 2 m, some colonial
Adults are sessile, larvae planktonic
3 layers of cells:Epidermal cellsMesohyl: gelatinous matrix withamoeboid cells; also contains carbonate or silica spicules or fibers of sponginChoanocytes: resemble the choanoflagellatesflagella create water current through sponge for nutrition (plankton) and oxygen supply; enter through pores, exit through osculum
Ground sponges regenerate; reproduction from broken pieces