Some members of this class are found in fresh water, some in ocean depths, and others in intertidal areas. Nearly all of these sponges contain spongin and some also have siliceous spicules with one to four rays.
These sponges mostly inhabit shallow water areas in the tropics.Ĭlass Demospongia - This class contains more than 90% of all living sponges. Sponges are classified based on the presence and kind of spicules.Ĭlass Hexactinellida (glass sponges) - Sponges of this class contain only six-rayed spicules made of silica.Ĭlass Calcarea - Calcareous sponges have spicules composed of calcium carbonate. A sponge's structure is maintained by spicules (needle-shaped, skeletal fibers of calcium carbonate or silica) or a kind of collagen protein called spongin.Sponges have an asymmetrical body shape.Some sponges release larvae in the initial stages of development while others retain the larvae for a while. The sperm is broadcast into the water through the sponges' osculum and taken in by other female-stage sponges of the same species to fertilize the eggs. Many sponges are hermaphrodites and produce eggs and sperm at different times. Sponge reproduction may be sexual or asexual.Sponges may be encrusting or found in a variety of upright forms and commonly colored red, orange, or yellow.Oxygen is also obtained from this current. Choanocytes filter out bacteria and other tiny nutrients from the water flowing through the sponge. Some sponges can pump as much as 20,000 times their volume through their tissues within 24 hours. Chambers within a sponge's walls contain cells called choanocytes with flagella (long, slender projections) that beat to create a current pulling water through the sponge's tissue.Water flows into the sponge through ostia (tiny pores in the outer wall), then through small canals into spongocoels (spacious chambers), and exits though larger holes called oscula (singular: osculum).The more than 5,500 sponge species share many common characteristics including the following: Nearly all sponges are marine and sessile (attached to the bottom or a hard substrate.) Sponges are simple animals without internal organs, muscles, or nerves. Invertebrates are a diverse group of animals including many phyla and classes.
Most of the animals in the tide pool are invertebrates - animals without backbones.