There are about 5,000 living species of sponges included in this phylum Porifera. All the species of this phylum are grouped into three classes depending mainly on the nature of the skeleton. They are both marine and fresh water forms. They live up to a depth of 8,500 m in the sea. They generally flourish in the warm waters. In the matter of size they are highly variable. Their size may vary from few centimeters to several meters.
The following is the classification of phylum Porifera:
Class I: Calcarea (L. Calcarius=limy)
- The sponges of this class are small.
- They all are exclusively marine forms living in shallow waters.
- Their skeleton is made up of calcareous spicules.
- Body many be cylindrical or vase like
- They may either live in colonies or solitarily
- Body organization may be asconoid, syconoid or leuconoid type.
- Development includes coeloblastula or amphiblastula larva
Ex: Clathrina, Leucosolenia, Scypha
Class II: Hexactanellida (Gr. Hex=six; Actin=ray)
- This class includes glass sponges.
- The sponges of this class are of moderate size.
- They all are exclusively marine forms living in deep waters.
- Their skeleton is made up of six-rayed siliceous spicules.
- Body may be cup, urn or vase like
- They may either live in colonies or solitarily.
- Development includes trichemella larva
Ex: Euplectella, Hyalonema
Class III: Desmospongiae (Gr. Demas=frame; Spongos=sponges)
- The sponges of this class are large sized.
- They include marine water or brackish water or fresh water forms
- Their skeleton is made up of siliceous spicules or sponging fibers or both or none.
- Body is vase or cup or cushion shaped
- They may either live solitarily or in colonies
- Body organization is leuconoid type
- Development includes parenchymula larva
Ex: Cliona, Spongia, Spongilla, Chalina
- Chart the classification of phylum Porifera.
- What is the meaning of the term Desmospongiae and Hexactanellida?
- Give the examples of the class Calcarea.
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