Nereis

         Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in nighttime to prey upon olive-sized 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 cleavable into acron, trunk and pygidium.  Acron is divisible into anterior prostomium and posterior peristomium and a allow out in between on the ventral nerve.   automobile 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 dorsal font and a pair of thread like anal cirri and several(prenominal) minute sensory papillae on the dorsal situation.  PARAPODIUM           Parapodia are blow locomotory organs of th e body attached on the lateral side of each trunk segment. Each parapodium is made of two lobes, that is to distinguish dorsally placed notopodium and ventrally placed neuropodium. Both lobes acquit 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 pompous columnar cells and disjoint ed glandular and sensory cells and is richly! supplied with decline vessels. Outer come 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. celoma          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: BestEssayCheap.com

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