In this article we will discuss about the T. S. body and parapodium of nereis.
T. S.Body of Nereis:
Fig. 127 T.S NEREIS
1. It is the slide of T. S. of Nereis.
2. The body wall is comprised of a’ outermost thin cuticle, a layer c epidermis and a thick layer of circular muscles.
3. The longitudinal muscles are not present as continuous layer, instead, they are arranged in the form of bundles two on dorso-lateral sides and two on ventrolateral sides.
4. In addition, there the present oblique muscle bands which divide the coelomic cavity into compartments.
5. In the centre is present a round gut enclosed in peritonium and attached to dorsal and ventral sides through mesentaries.
6. Below the dorso-lateral longitudinal muscle bundles, attached to them, are present th eciliated organ.
7. The coelomic cavity is lined with ciliated epithelium and around the gut the space is filled with germ cells in different stages of development.
8. On either side of the main body is present a parapodium which is comprised of notopodial and neuro-podial lobes and dorsal and ventral cirri.
9. Each lobe is supported with a chitinous rod-the aciculum.
10. The inner end of aciculum is connected with muscles and the outer lateral end bears a bunch of chitinous setae.
11. The muscles control the movement of aciculum arid setae help in swimming.
12. Above the gut inside the mesentery is present the dorsal blood vessels and below the gut lies a ventral blood vessel and ventral nerve cord.
Parapodium of Nereis:
1. It is the slide of parapodium of Nereis.
2. The parapodium is biramous and lies on either side of a segment and is the organ of locomotion (swimming).
3. It comprises a dorsal notopodial and a ventral neuropodial lobe.
4. Each lobe is supported internally by a chitinous rod-like – aciculum.
5. The aciculum bears numerous pointed and serrated setae.
6. Above the notopodium is present a dorsal cirus and below the neuropodium is present a ventral cirrus.
7. Foliacious outgrowths are absent.