CHARACTERS AND CLASSIFICATION OF PORIFERA

Robert E. Grant, used the term of porifera in 1839. Meaning of porifera is pore bearer. Therefore, those organism in which body bears pore are called porifera.

 

CHARACTERS:-

• Porifera are diploblastic i.e., the two layers are found in the body (Ectoderm and Endoderm).
• The animals of porifera are multicellular.
• All animals of porifera are marine found in sea water (except spongilla, fresh water).
• These are plant like fixed and generally cylindrical in shape.
• Over body surface, pore or ostia are found. From the ostia water enters into the body.
• Definite organs and systems are not found. It has cellular level of body organization. 
• Digestion intracellular.
• Water current enters in the body helps in feeding and respiration, reproduction and excretion.
• Nervous system absent.
• Reproduction takes place by asexual and sexual method.
• Asexually reproduction by budding. Sexual reproduction by gametes or sperms and ovum.

The whole body is formed of 3 types of spicules. Spicules helps as Skeleton. On the basis of spicules, Phylum porifera has been classified into 3 classes-

1. Calcarea or calcispongae
2. Hexactenillida or Hyalospongae
3. Desmospongae

Class- Calcarea

• In this class calcareous spicules are found.
• In this class small sponges are found. These sponges are found all over the world in sea water.
• Canal system is found either Ascon type or Sycon type.
• This class has been divided  into 2 orders-

1. Homocoela
2. Heterocoela

 

Order -  Homocoela

• The body is simple cylindrical.
• The inner most layer of body is lined with flagellated collar cells.
• Body wall thin.
• Canal system Ascon type.

Example – Lecucosolenia

• Spongocoel is lined by flagellated cells.

 Order- Heterocoela

• Spongocoel lined by flat cells.
• Flagellated cells found in flagellated chamber.
• Body wall thick and folded.
• Complicated type of canal system syconoid or lecuconoid type.

Example :- Sycon or Grantia

Class :- Hexactenillida

• In this class large size sponges are placed.
• These sponges are found depth of sea, nearly 300 ft below.
• Sponges are cylindrical, Cup shaped, funnel like, pitcher like, flower vase like etc.
•  Spicules are triaxon type.

• Body glass like beautiful. e.g., glass sponges (Hyalonemma)
• Canal system Rhagon type.
• This class has been divided into 2 orders-

1. Hexasterophora
2. Amphidiscophora

 

Order :- Hexasterophora:

• In the mesenchyme Hexasters spicules present.

• Body skeleton frame like, irregular.

e.g :- Euplectella  (Venous flower basket)

 

Order :- Amphidiscophora

• Hexasters absent, but amphidiscs monoxon spicules present.
• Both sides of spicules bear crown of rays.

• Sponges are spiral rope like. e.g :- Glass sponges.

 

Class :- Desmospongia

• Skeleton are absent in this class of sponges.
• In some sponges, Spongian fibres or siliceous spicules present.
• All are generally marine.
• Body rounded, cup shaped or club shaped.
• Canal system Leucon type.
• This class has been divided into 4 orders :-

1. Tetractenillida
2. Monoaxonida
3. Keratosa
4. Myxospongia

 

ORDER :- TETRACTENILLIDA

• Tetraxon spicules present, sometimes spicules absent.
• Sponges are round or flat. e.g :- Chondrilla

ORDER:- MONAXONDIA

• Monaxon Spicules present.
• Shape flask like, branched, found attached with  Mollusca shell. e.g :- Cliona, fresh water Spongilla.

ORDER :-  KERATOSA

• Spongilla spicules present.
• Body rounded leathery. e.g.:- Horse sponge.

ORDER :- MYXOSPONGIA

• Skeleton absent in this type of sponges.
• Body blistering. e.g :- Oscarella ( Blacksponges), Heliosarca   
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