Porifera : General Characters and Examples

 

Porifera : Defination 

• These are invertebrate primitive multi cellular animal with cellular grade of organisation. 

General characters

• Members of this phylum are commonly known as sponges. They are generally marine and mostly asymmetrical animals.

• These are primitive multicellular animals and have cellular level of organisation. 

• Sponges have a water transport or canal system. 

• In canal system Water enters through minute pores called ostia in the body cavity named spongocoel, from where it goes out through the osculum. 

• This pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste. 

• 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 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.

Archeocytes are totipotent cells in sponges and also called amobeocytes.
Thesocytes are cells in sponge which store food.
Parenchymula is larval stage of sponges.

Examples of Porifera 
1. Sycon
Sycon is  marine and also known as Scypha.
It is found to attach with rock, coral and molluscan shell.
Sycon has exoskeleton made up of spicules therefore it belong to  class calcarea.
Sycon has ascon type of canal system. The path of water current is - Ostia - incurrent canal - Prosopyles - radial canal - apopyles - Spongocoel - osculum.
 The length of Sycon varies   from 2.5 to 7.6 cm and       they have the capability to   regenerate their lost body   parts. 
2. Euspongia 
It is commonly called as Bath sponge because used in clearing tool.
It has exoskeleton made up of sponging fibre therefore it belong to  class Demospongia. Spicules are absent in Euspongia.
It is found in Mediterranean sea as well as American. Sea coast.

Euspongia can reproduce sexually by internal Fertilization with indirect development.
It also reproduce asexually by fragmentation , budding and  regeneration.
It is globular   in shape with numerous oscula mounted on well marked projections-the canals.
3. Spongilla 
It is commonly called as fresh water sponge and atteched with submerged plant, stick etc.
The body colour of spongilla depends on Zoo chlorella which is present as symbiotic partner with spongilla.
The body of spongilla is supported by both Spicules and sponging fibers.
It has a complex leucon type of canal system.The path of water current is - Ostia - incurrent canal - flagellated chamber- Excurrent canal - Spongocoel - osculum.
Spongilla can reproduce sexually by internal Fertilization with indirect development.
It also reproduce asexually by budding and  gemmule formation.