Phylum Porifera:
- Members of this phylum are commonly known as sponges.
- They are generally marine (Except Spongilla, its fresh water sponge)
- Mostly asymmetrical animals
- These are primitive multicellular animals and have cellular level of organisation.
- Sponges have a water transport or canal system.
- Water enters through minute pores (ostia) in the body wall into a central cavity, spongocoel, from where it goes out through the osculum.
Functions of water transport /canal system in sponges. This pathway of water transport is helpful in:
- Food gathering
- Respiratory exchange and
- Removal of waste
Water --> Ostia --> Spongocoel --> Osculum
- Choanocytes or collar cells line the spongocoel and the canals
- Digestion is intracellular
- The body is supported by a skeleton made up of spicules or spongin fibres.
- Sexes are not separate (hermaphrodite), i.e., eggs and sperms are produced by the same individual.
- Sponges reproduce asexually by fragmentation and sexually by formation of gametes.
- Fertilisation is internal and development is indirect having a larval stage which is morphologically distinct from the adult.
- Examples: Sycon (Scypha), Spongilla (Fresh water sponge)
