General Characteristics and Classification of Porifera

By Nitul Kalita


General Characteristics













Classification


Phylum Porifera has been divided into three class which are-

Class1- Calcarea

Class2- Hexactinellida

Class3- Demospongea


CLASS 1: CALCAREA 

 • These are small sized calcareous sponges (10cm in height). 
 • Solitary or colonial.
 • Body cylindrical or vase like in shape.
 • Skeleton formed of calcareous spicules which may be one, three, or four rayed.
 • All are marine animals.
 • Body organisation may be asconoid, Syconoid or lenconoid type. 

 ORDER-1 HOMOCOELA 

• Asconoid sponges with radially-symmetrical and cylindrical body. 
• Body wall thin and unfolded; choanocytes line the spongocoel.
• Often colonial. Example- Leucosolenia, Clathrina 

 ORDER-2 HETEROCOELA

 • Syconoid and leuconoid sponges with thin walled vase shaped body.
 • Choanocytes are found in radial canals or inflagellated chambers only. Example-Schypha,Grantia

CLASS 2: HEXACTINELLIDA

• Generally hyalospongiae are found in medium sized sponges but some time few sponges reached one meter in length.
• It is commonly known as glass sponges.
• Its body shape cylindrical, funnel shaped or cup shaped.
• The canal system was very typical and body organization Syconoid type.
• Hexactinellida class is found in deep marine water. ORDER-1 HEXASTEROPHORA 
• Spicules are star shaped (six-shaped) eg., hexasters 
• Flagellated chambers regularly and radially arranged.
• Usually attached to substratum directly. Example-Euplectella (Venus’s flower basket) 

CLASS-3: DEMOSPONGIAE 

• Solitary or colonial.
• Its body is cup or vase shaped. 
• Demospongiae showed both small and large size. 
• Spicules are seen monaxon or tetraxon
• The canal system is leuconoid type. 
• All are marine porifera but except freshwater sponges (Spongillidae).
 • The class Demospongiae is classified into the three sub classes. 

SUBCLASS: 1 TETRACTINELLIDA

• Spicules siliceous and four rayed (tetraxon) or absent. 
• Spongin fibres are absent.
• Mostly found in shallow water. 
• Subclass Tetractinellida has been divided into three orders- 

 ORDER1- MYXOSPONGIDA 

• Both spicules and spongin fibres are absent.
• Structure simple. Example- Oscarella 

ORDER2- CARNOSA 

• Micro and are indistinct. 
• All spicules are monaxons. Example- Chondrilla and Plankia. 

ORDER3- CHORISTIDA 

• Micro. Tetraxon spicules with long axis. Example-Thenea, Geodia

SUBCLASS:2 MONAXONIDA

• Spicules monaxon and siliceous type.
• Spongin fibres some time present or absent.
• Mostly monaxonida is occurring in shallow water. 
• Some subclass lives in deep sea but some found in fresh water. 

 ORDER1- HADROMARINA 

• Spongin fibres absent. 
• Microscleres star shaped when present. Example- Cliona  (Boring sponge that bores in molluscan shell)  

ORDER2- HALICHONDRINA 

• Spongin fibres very little. 
• Microsclers usually absent. Example-Halichondria

ORDER3- POECILOSCLERINA

• Large spicules or megascleres of many types and united with spongin fibres and form network. 
• Microscleres C-shaped. Example- Microciona 

 ORDER4-HAPLOSCLERINA

 • Megascleres are only of one type having 2-rays only.
 • Microscleres may be present or absent.
 • Spongin fibres present. Example- Spongilla and Chalina 

SUBCLASS: 3 KERATOSA

• Generally spicules are absent in subclass Keratosa.
• The subclass Keratosa consists of horny sponges. 
• Skeleton contains spongin fibres only. Example- Horse sponge (Hippospongia) and Bath sponge
 ( Euspongia)

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