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Biodiversity Introduction > Porifera > Cnidaria > Polychaeta > Crustacea > Mollusca > Bryozoa > Echinodermata
The sponges are sessile suspension feeders, and most species are marine. Feeding occurs by circulating seawater through the sponge, removing nutrients before being expelled through the osculum. Some sponges have a rigid skeleton made of either calcium carbonate, silica or collagen. The sponges associated with cold-water coral reefs are diverse, both taxonomically and morphologically. While many sponges on these reefs encrust hard substrata within living reef frameworks and coral rubble habitats, large glass sponges ( Hexactinellida) are particularly conspicuous part of the reef fauna and form delicate habitats themselves. In the north Pacific, large cold-water sponge reefs have recently been discovered. The Porifera also exhibit a spectrum of bioactive chemicals with potentially pharmaceutical applications: the diversity they support and their socioeconomic value for humans must help to ensure the protection of both cold-water sponge and coral reef habitats.
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The Phylum Porifera refers to the sponges. These animals are distinguished from all others in that they lack a true organisation of cells into body tissues, and are not considered true colonial animals. Most sponge cells are therefore totipotent: one cell type can change into other cell types as the sponge requires. This is a distinct advantage for sponges, as they can fragment into two or more individuals and then re-constitute each new fragment into a new separate sponge, a form of asexual reproduction.
