Porifera (sponges), class: DemospongiaeCollection Highlights | Updated 6 years ago Ianthella flabelliformis Photo by Clay Bryce, image copyright WA Museum The demosponges comprise 95% of the world's sponges and include the most colourful species. They range in size from small, encrusting forms, through to large irregular masses. They have spicules (tiny needle-like structures that support the body’s form) of silica dioxide and/or spongin. Demosponges are the sponges most commonly seen whilst diving or walking along the shore. Unlike the other two classes whose members are all marine, demosponges can also be found in freshwater. In the past, these sponges were used as bath sponges. The above-mentioned spongin gave them both softness and absorbent qualities. Demosponges can reproduce both sexually and asexually (this occurs when the parent breaks down to begin budding and release gemmules). Marine Invertebrates Section View the discussion thread.