Phylum Porifera The Sponges

Characteristics of Sponges No definite symmetry Multicellular, few tissues, no organs No true body cavity (water filled space) Sessile as adults (live attached to something) Reproduce sexually or asexually Have no nervous system Larval stage planktonic Live in water Filter feeders Often have skeleton of spicules

Symmetry None Radial Bilateral

General Information Simplest of all animals Over 600 million years old ~ 5000 species, mostly marine Important reef organisms 3 groups of sponges Classified based on what spicules are made of and how many rays

Classification Calcarea Sponges: 1, 3, or 4 rayed spicules made of calcium carbonate Demospongiae Sponges: 1, 2, or 4 rayed spicules made of silica Hexactinellida Sponges: 6 rayed spicules made of silica (glass sponges)

Encrusting sponges cover rocks in a thin layer instead of forming tall tubes

Anatomy Body made of single layer of flagellated cells Canals have openings to outside (ostia) Water enters sponge through ostia Exits through osculum Spongocoel: center canal

Choanocytes Canals lined with flagellated cells (choanocytes) Choanocytes beat flagellum to keep water flowing in correct direction Trap food Help larval form swim

Body Types 3 Body Types Asconoid: simplest, single choanocyte-lined canal Syconoid: canals branched & choanocyte-lined (spongocoel: no choanocytes) Leuconoid: most complex, many branches, choanocytes only in special chambers

Reproduction Most sponges are hermaphrodites (both male and female) Only one gender at a time Areas of cells will change into egg or sperm Sperm released through osculum of “male” sponge Sperm enters “female” sponge and fertilize eggs Larvae released, float for a few days, then settles

Sponges can also reproduce asexually Pieces (gemmules) will break off, settle, and develop into a new sponge

Feeding Strategies Filter Feeders Water flowing through ostia carries bacteria and small organic particles Oxygen also absorbed from water Waste removed as water flows through

Weird But True Carnivorous Sponge discovered deep Antarctic waters Eats small crustaceans Spicules act like Velcro Cells surround prey and dissolve

Human Use Humans collect and dry sea sponges to use in the shower