The Porifera are a well-characterised group of aquatic, predominantly marine animals including about 5000 described species. These animals are distinct from the Protozoa in having a cellular construction, and from other Metazoa in the absence of true tissues and in the possession of an elaborate filter feeding apparatus. The latter is based on an extensive system of pores and canals and powered by the action of peculiar flagellated cells, the choanocytes. Support for the soft structures of the sponge body is provided by calcareous or siliceous spicules, by organic fibres, or by a combination of fibres and spicules.
Unable to display preview. Download preview PDF.