Question

Discuss the special feature of sponges.

OR

Enumerate the general characters of the phylum porifera. Give two examples.

Answer 1

The sponges belonging to the phylum Porifera exhibit the following features.

• Primitive multicellular Organisms with cellular grade of Organisation.
• They are exclusively aquatic, largely marine, very few freshwaters. 
• The adult forms are sessile (attached) but the larval forms are freeswimming.
• The body is asymmetrical or radially symmetrical.
• The body wall is diploblastic with choanoderm (endoderm) and pinacoderm (ectoderm) and mesoglea in between.
• The body surface bears large numbers of microscopic process called Dermal Ostia. The body cavity is called spongocoel which opens outside by Osculum.
• The spicules formed of calcium carbonate or silica form the internal skeletal support. 
• Sponges reproduce by asexual, sexual and by gemmule formation. The larvas of sponges is called Amphiblastula or Parenchymula. Examples: Scyon and Euspongia.