Nereis

         Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in darkness to prey upon downcast animals. N. virens  (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis.           Body of Nereis is dorsoventrally flattened, segmental and 30-40 cm long having 80 to 120 segments and divisible into acron, trunk and pygidium.  Acron is divisible into anterior prostomium and posterior peristomium and a let out in between on the ventral nerve.   tree trunk is metamerically segmented and segments are called metameres or somites each one of which bears a couplet of parapodia. The last segment is called pygidium that bears an anus slightly on the abaxial font and a pair of thread like anal retentive cirri and several(prenominal) minute sensory papillae on the dorsal facial expression.  PARAPODIUM           Parapodia are verso locomotory organs of the body attached on the lateral side of each trunk segment. Each parapodium is made of two lobes, that is to verbalise dorsally placed notopodium and ventrally placed neuropodium. Both lobes exonerate thread-like appendages called dorsal and ventral cirri.

The two lobes of parapodium are supported internally by two chitinous rods known as aciculum, on the apical part of which at that place are bundles of long, chitinous setae or chaetae which project beyond the outer(prenominal) margin.  Nephridiopore is situated on the parapodium snug the ventral cirrus. SKIN          Skin is made of magniloquent columnar cells and disjointed glandular and sensory cells and is richly supplied with race vessels. Outer c! ome along of epidermis is coated with a layer of tough cuticle which carries a number of small pores for glands. Below the epidermis there are circular and longitudinal passs in bundles and some abdominal external oblique muscle strands that help to carry out lateral undulation of body. coelom          The celom is schizocoelom but true perivisceral cavity that is made of an outer parietal peritoneum and an inner visceral peritoneum that surrounds the alimentary...If you want to get a just essay, order it on our website: OrderEssay.net

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