NEREIS

CLASSIFICATION OF NEREIS

PHYLUM :- ANNELIDA (Metamerically segmented, coelomate and laterally symmetrical. )

CLASS :- POLYCHAETA (Many setae, clitellum absent. )

ORDER :- ERRANTIA (Free-swimming or burrowing, pharynx protrusible, provided with jaws and teeth. )

GENUS :- Nereis (Rag worm or Clam worm)

GEOGRAPHICAL DISTRIBUTION

It has cosmopolitan distribution found along the North Atlantic coast, Pacific coast, u.S.A. and Europe.

HABIT AND HABITAT

  • Nereis is a marine crawling type, living in temporary burrows in sand, 200 meters deep. They are free-living, predaceous, nocturnal, carnivorous, often found buried in the intertidal sad.
NEREIS

GENERAL CHARACTERSTICS OF NEREIS

  • Commonly called as Rag worm or Clam worm and is the simplest annelid.
  • Examination of preserved specimen shows cylindrical and elongated body form which is divided into similar metameres or segments about 200 in number.
  • First few segments fuse to form head which is composed of (i) prostomium or preoral lobe, which carries prostomial tentacles, palps and ocelli; and (ii) peristomium (2 segments fused), which carries antero-laterally 4 pairs of peristomial tentacles. 
  • Mouth is found on the anterior surface of the peristomium.
  • Body segments, except head and anal segment, contain each pair of locomotory parapodia.
  • Segments are also called as metameres and between two segments in intersegmental groove. 
  • Parapodia also serve as respiratory and circulatory organs. Each parapodium is composed of dorsal notopodium and ventral neuropodium. Parapodium also possesses aciculum for support and needle like setae for crawling.
  • Anal segment contains a pair or anal cirri. 
  • Nereis is dioecious, although male and female worms can hardly be recognized.
NEREIS

IDENTIFICATION

  • The animal has prostomium, peristomium, parapodium and all above features and hence it is Nereis.

NEREIS
NEREIS
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