phylum+porifera

ZOOLOGY NOTES—THE PORIFERANS

THE METAZOANS MULTICELLULAR ANIMALS

KINGDOM ANIMALIA PHYLUM PORIFERA THE SPONGES

SPONGE FACTS 5,000 –10,000 species are known Most are marine, only about 150 species are freshwater Thousands of pores allow water to flow through the sponge, bringing nourishment and oxygen to its cell

SPONGE ANATOMY The body of a sponge has two layers separated by an acellular (with no cells) gel layer The gel layer contains either spicules (needles made of calcium carbonate) or spongin (protein) No tissues or organs are present Shapes include tubes, fans, cups, cones, barrels, and crusts Size from a few millimeters to 2 meters tall

SPONGE DIET Most sponges eat tiny bacteria, algae, or protozoans that they filter from the water that flows through their body

REPRODUCTION Most are hermaphrodites which produce both eggs and sperm Released sperm randomly float through the water to other sponges Fertilization takes place if a sperm is caught by another sponge’s collar cells The resulting larva swims using cilia to propel it through the water The larva settles on the sea floor and becomes sessile as it grows to an adult Sponges can also reproduce asexually by budding or producing gemmules

SPONGE CLASSIFICATION

CLASSES OF SPONGES Sponges are classified based upon the structure of their skeleton and upon their body type Spicules can be made of calcium carbonate or they can be made of silicon They can have several shapes, and are named based upon the number of rays that are present Asconoid body type is the most simple, with small pores emptying into a central cavity called the spongocoel Syconoid body types have radial canals that are lined with choanocytes emptying into the spongocoel Leuconoid body types are the most complex. They consist of chambers lined with choanocytes. Incurrent canals lead into these chambers and excurrent canals empty into the osculum

CLASS CALCAREA The spicules of this class are made of calcium carbonate, and are straight or have three or four rays All three body types are present Most are small and tubular or vase-shaped Example—//Grantia//

CLASS HEXACTINELLIDA Size of about 7.5 cm to 1.3 meters in length Rigid skeleton of six-rayed silaceous spicules Syconoid and leuconoid body types Deep-sea dwellers EXAMPLE—Venus’ Flower Basket

CLASS DEMOSPONGIAE Includes 95% of all sponges Skeleton consists of silicon spicules which are NOT six-rayed, and/or sponging Body type is leuconoid One family is freshwater and forms gemmules in late autumn EXAMPLE—Dead Man’s Finger