Phylum Annelida

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Classification of Phylum Annelida by Rupert & Barnes (1994)

Phylum :- Annelida

Characters :-

(i) The body is metamerically segmented, the division of the body into similar segmented are arranged in a linear series along the anterio posterior axis.
                    
(ii) The body cavity is true coelom, which is lined by a peritoneum or coelomic epithelium & serves as a hydrostastic skeleton against which muscles can contrast.
                    
(iii) Body cavity often subdivided by transverse septa.
                    
(iv) Presence of muscular gut with mouth & anus.
                    
( v) Closed blood circulatory system.

Class :- Polychaeta

Characters :-

(i) Predominantly marine with errants & sedentary habit.
                  
(ii) Distinct head bearing eyes,tentacles,cirri & palps.
                  
(iii) Pharynx with or without jaws or teeth.
                  
(iv) Presence of numerous chaetae or bristles, inserted in two groups in the biramous segmental parapodia.



Examples :- Nereis; Aphrodite; Chaetopterus; Sabella;

Nereis

Class :- Oligochaeta

Characters :-

(i) Head indistinct, prostomium is either small, rounded lobe or a small cone without appendages.
                  
(ii) Body segment lack parapodia but have setal sacs from which setae as group of bundle.
                  
(iii) Presence of clitellum.
                  
(iv) Hermaphrodites with distinct gonads restricted usually to a few anterior segments.



Examples :- Pheretima; Lumbricus; Tubifex; Megascolex;

Pheretima

Class :- Hirudinaria

Characters :-

(i) Dorsoventrally flattened, pigmented body made of 33 segments, marked externally by secondary rings or annuli.
                  
(ii) Usually two suckers are present a powerful posterior sucker & small anterior or head sucker surrounding the mouth.
                  
(iii) Tentacles, parapodia & setae are absent.
                  
(iv) Coelom much reduced & filled by connectives tissues.



Examples :- Hirudinaria; Hirudo; Acanthobdella;