Question

Name the locomotory structures of Nereis.

Answer 1

Hint: Nereis is a type of worm which belongs to phylum Annelida. A very particular feature found in all annelids is the presence of multiple segments on the body. Each of the segments has a pair of locomotory structures.

Complete answer:
Nereis is a marine worm belonging to the phylum Annelida. It possesses parapodia as locomotory structures. Each parapodia has two types of setae. The ones which provide support are called as acicular setae and the ones which are used for crawling are called as locomotor setae. These setae also have bristles which are easily visible.
Body of nereis is cylindrical in shape and they are mostly burrowing worms. Body is long, slender and dorso-ventrally flattened. They are commonly known as rag or calm worms. They rarely gather in large groups but are found clinging to seagrass. Nereis is dangerous to touch barehanded as it stings and the burns are extremely painful.
Their head consists of two parts -prostomium and peristomium. The prostomium is roughly of a triangular shape and is the anterior lobe. Peristomium is ring like, posterior in position and bears tentacles which are terminal. It also has two pairs of eyes present dorsally.

Note: Nereis shows an exceptional feature that it maintains its internal environment which is equal in concentration to its surrounding. Also, the pressure inside the cells of the body and pressure of the surroundings is equal. Such organisms are called osmoconformers.