Phylum Cnideria

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Classification of Phylum Cnideria according to Ruppert & barnes(1994)

Phylum :- Cnideria

Character :- 

(i) Body diploblastic i.e, composed of two tissue layers, an outer epidermal (ectoderm) & an inner gastrodermis (endoderm) with several to many cell types & a less cellular mesoglea at the centre.

                   

(ii) Two different body forms may exist a 'medesa' (sexual) adapted for pelagic existence & a polyp(asexual) adapted for benthic existence.

                   

(iii)Short & slender tentacles encircles the mouth in one or more whorls.

                  

 (iv)The body composed of a special types of cell, called of Cnidocytes, containing stinging organelles called Nematocysts.

                   

(v) In the body there is an internal space for digestion, the gastrovascular cavity with the mouth as the only opening.

Class:- Hydrozoa

Characters :-

(i) Individuals are either exclusively polypoid or medusoid or constituted by both forms in the life cycle.

(ii) Mesoglea acellular.

(iii)Cnidocytes are confined to the epidermal layer.
                  
(iv)Gonads are usually ectodermal in origin.

Examples :- Hydra; Obelia; Physalia; Velella; Porpita;

                                     Hydra

Class:- Scyphozoa

Characters :- 

(i) Medusoid form is dominant in the life cycle, polypoid forms is very insufficant.
                
(ii) Mesoglea is cellular.
                
 (iii)Gonads are endodermal.
                
 (iv)The endodermal gastric tentacles are present.

 Examples :- Aurelia; Pilema; Pericolpa;

                               Aurelia

Class:- Cubozoa

Characters :- 

(i) Medusoid cnidarians with bells.
                
(ii) Body is distinctly flattened to form four sides.
                  
(iii) Bell margin simple.
                  
(iv) Presence of velum along the margin of the medusa.

Examples :- Carybdea; Chironex; Chiropsalmus;

                   Carybdea

Class:- Anthozoa

Characters :-

(i) Exist only in the polypoid form.
                  
(ii) Gonads are endodermal.
                
(iii) Stomodium strongly developed.
                  
(iv) Extending between the stomodaeum & the body wall there are mesenteries.


Examples :- Gorgonia(sea-fan); pennatulla(sea-pen); Corallium; Fungia;

Gorgonia(sea-fan);