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Phylum Porifera

(Porus = Pore; Fere= to bear )

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General Characters

01) Porifera are generally aquatic, mostly marine.

02) They are sessile and sedentary and grow like plants.

03) Body is cylinder like, asymmetrical or radially symmetrical.

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04) The body surface is perforated by numerous pores, the OSTIA through which the water enters the body and one or more large openings, the OSCULA by with the water passes out.

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05) Body is multicellular having outer ectoderm and inner endoderm with an intermediate layer of mesenchyme, there fore diploblastic animal.

06) The interior space of the body is holloow and interior space of sponge body called Spongocoel.

07) Mouth absent, digestion intracellular.

08) Excretory and respiratory organs absent.

09) The nervous and sensory cells are probably not differentiated.

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        • The sponges are monoecious reproduction both by asexual and sexual method .

11) The sponges passes hing power of regeneration.

  1. Sexual reproduction occurs by ova and sperms.
  2. Fertilization is internal, but cross fertilization occurs in a rule.
  3. Asexual reproduction occurs by buds and gemmules.

15) Cleavage holoblastic, development indirect through a free swimming ciliated larva called amphiblastula.

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16) Ex:- Sycon, Euplectella, Hyalonema,

Euspongia, Spongilla.

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    • The Phylum Porifera is classified in to following three classes.

A) Calcispongiae or Calcarea.

Ex: Sycon.

B) Hyalospongiae or Hexactinellida.

Ex: Euplectella.

C) Demospongiae.

Ex: Euspongia.

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CLASS I CALCISPONGIAE �(CALY= LIME; SPONGOS= SPONGE)

Ex: Sycon (Scypha)

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  1. These sponges are called as lime spongae.
  2. They have a skeleton of separate calcareous spicules. Which are monaxon or triaxon, tetraxon spicules lose one ray to become triradiate.
  3. They are solitary or colonial.
  4. Body shape vase like or cylindrical.
  5. They show asconoid, syconoid or leuconoid structure.
  6. They are dull coloured sponges less than 15 cm in size.
  7. They occur in shallow water in all oceans.
  8. Ex: Sycon, Grantia, Leucosolenia, Clathrina.

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CLASS II HYALOSPONGIAE �(HYALOS= GLASSY; SPONGOS= SPONGE)

Ex: Hyalonema

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  1. These sponges are called as glass sponges.
  2. Skeleton is of siliceous spicules, which are triaxon with six rays. i.e. star like shape.
  3. In some spicules are fused to form a lattic-like skeleton.
  4. Ther is no epidermal epithelium.
  5. Choanocytes like finger shaped chambers.
  6. They are cylindrical or funnel shaped.
  7. Glass-sponges are found in deep tropical seas.
  8. They grow up to one meter or three feet.
  9. Ex: Hyalonema, Pheronema Euplectella, Farnera.

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CLASS III HYALOSPONGIAE �(DEMOS= FRAME; SPONGOS= SPONGE)

Ex: Euspongia

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  1. Generally marine, few may be fresh water forms.
  2. It is called as frame spspongae.
  3. It contains the largest no. of spongae species.
  4. They are large sized, Solitary or colonial.
  5. The skeleton may be of spongin fibres or of spongin fibres with slilceous spicules or there may be no skeleton.
  6. Spicules are never six-rayed, They are monaxon or tetraxon and are differentiated into large megascleres and small microscleres.
  7. Body shape is irregular, the canal system is of leucon type.
  8. Ex: Euspongia, Spongilla.

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