Nereis

-:Nereis:-

Or

-:Neanthes:-

(Clam warm)

Systematic position:-

Phylum-.  Annelida

Class-       Polychaeeta

Order-.           Errantia

Family-.         Nereidae

Genus-.     Nereis

Species-.         Virens

Distribution :-
              Nereis is cosmopolitan* in distribution. It is found abundantly in Europ, North America etc.

-:External Structures:-

i.Shape:-
        Body is elongated, slender Bilaterally symmetrical and slightly flattened*
ii.Size:-
            Length is varries from few to 40 cm or more.
iii.Colour:-
             The colouration is varies from species to species like- Brown, Greenish,Steel blue
*सर्व्यापी
*चपटे
 

Segmentation:-
                 The body of Nereis is segmented that is called metameres or somites. The  number of segments varies from 80-200. This type of segmentation is called metameris

-:Division of the body:-

The body of Nereis is divided into three parts:-
i. Head:-
           The anterior portion of the body is head that include two parts
(a). Prostomium (Pro=before+Stoma= Mouth)
It is anterior, triangular, fleshy outgrowth and is not true segment. It do not possess mouth. The prostomium bears following structures-
>Prostomial Tentacles- paired, cylindrical,small,and placed,in front.
>Palp- paired, elongated and compact and located after the tentacles.
>Eyes- two pairs,simple, round,pigmmented and present on the dorsal side of the head
(B) Peristomium:-
It is large ring like structure that ventrally has mouth.The peristomium carries-
>Peristimial tentacles-four pairs long slender, cylindrical,and laterally placed.
>Mouth-present on the ventral side as a transverse aperture.
ii. Trunk:-
             Posterior part of the head with metamericaly segmented is called trunk. The segments of trunk bear Parapodia all alike except last.
iii. Pygidium
                The last segment of the body is Pygidium which bears a terminal anus. It do not posses Parapodia,but single pair of cirri