Phylum: Porifera (sponge), its classification and characteristics

  •  Multicellular, eukaryotic with cellular grade of body organization.
  • Aquatic, mostly marine few found in fresh water.
  • Solitary or colonial, free living.
  • Sedentary and sessile.
  • May be asymmetrical (Spongilla) or radially symmetrical (Leucosolenia).
  • Body greatly varies in shape. They may be vase-like, cylindrical, tubular or cushion like.
  • Body is provided with large number of small inhalant pores called ostia (sing- ostium).
  • One or few large exhalent pores are present called oscula (sing- osculum).
  • Inter hollow body is present called spongocoel, lined by flagellated cells called choanocytes.
  • Diploblastic. Outer layer is pinacoderm (ectoderm) and inner layer is  choanoderm (endoderm).
  • In between these layers, jelly like layer is present called mesenchyme (mesohyl or mesogloea).
  • Mesenchyme contains collagen fibers, skeletal elements, and amoebocytes.
  • Nervous and sensory cells are absent.

Kingdom animalia - Phylum Porifera

                                                                              Image source: weebly

  • Skeletal elements are calcareous, silicious or formed of spongin fibers.
  • Well developed water canal system which help them in feeding, respiration, excretion, etc.
  • Have great power of generation.
  • Reproduction occurs asexually by budding or formation of gemmules. sexual reproduction occurs by fusion of gametes.
  • Indirect development occurs which include free swimming, larval forms called amphiblastula or parenchymula.


Poriferans are divided into 3 classes on the basis of spicules or skeletal elements. They are :

Class 1 : Calcarea

  • exclusively marine.
  • calcareous spicules.
  • solitary or colonial.
  • osculum is always encircled by a fringe of upstanding spicules.
  • small sized sponges, less than 10 cm in length.
  • body shape cylindrical and vase-like.
  • examples: Sycon (crown sponge), Grantia, Leucosolenia, Clathrina

Unit 5-1: Phylum Porifera – The Biology Classroom

 Image source: blogsubc

 Class 2 : Hexactinellida

  • exclusively marine.
  • six rayed triaxoned glass like silicious spicules.
  • mostly solitary.
  • commonly called glass sponges.
  • grow up to 92 cm in length.
  • cylindrical or funnel shaped or vase-like.
  • examples : Euplectella (venus flower basket), Hyalonema (glass rope sponge).


Image source: faunafondness

Class 3 : Demospongiae

  • mostly marine, few are found in fresh water.
  • skeletal elements formed of calcareous spicules, monoaxoned or tetraaxoned silicious spicules, spongin fibers or both or absent.
  • spicules are never six rayed.
  • small or large sized.
  • solitary or colonial.
  • examples : Euspongia (bath sponge), Spongilla (Fresh water sponge), Plakina, Oscarella.




Phylum: Porifera (sponge), its classification and characteristics