Description Sponges are the most primitive of the multicellular invertebrates. They lack a mouth and gut. The bodies are organized around a system of water canals.
Sponges feed, breath, reproduce, and excrete by means of pumping water through their body.
Their size is correlated to ocean current velocity and other factors such as availability of space and inclination of the substrate. These traits are helpful in identifying the sponge species. The sizes are very diverse. Range and Habitat Most species are marine and are found at all depths. Many animals use sponges for shelter.