Porifera
Porifera (Spongiaria, sponges) A phylum of aquatic Animalia, most of which are marine. They lack definite tissues and organs, but have a filter-feeding system composed of flagellate cells, pores, and canals. Most are covered externally by either a cortex or a dermis. The soft body may be supported by a skeleton composed of collagen, with or without siliceous or calcareous spicules, protein spongin fibres, or a combination of the last two. The body shape is very variable, being influenced by the substratum and water currents (e.g. where the water movement is very strong, sponges often grow as rounded clumps, but in calm water they may assume branching shapes). Sponges have remarkable powers of regeneration, small, broken pieces being capable of growing into a whole animal. Larvae are motile and produced by sexual reproduction. The phylum ranges from the Cambrian to the present.
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Porifera
