Question

In earthworm, setae are present in all segments except
(A) First and the last segments
(B) First segments
(C) Clitellum and last segments
(D) First, clitellum and last segments

Answer 1

Hint: Earthworm belongs to the phylum Annelida. Earthworms don’t have legs. They have a special locomotory for movements of earthworms. These structures are known as setae.

Complete answer: Earthworm is an organism which belongs to the Annelida phylum. It is a cylindrical shaped organism. There are around 100 segments. That’s why the body is known as metamerism.
Earthworms have setae which are S- shaped. These setae are found in rows on the body of an earthworm. These are found in the middle position of each segment. Setae are found in every segment except first, last and clitellum.
First segment is known as peristomium which consists of the mouth. Last segment is known as pygidium. Clitellum is found in mature earthworms. It is found between 14-16 segments of earthworm. It is a band of dark color which consists of glandular tissues.
Setae are embedded in the epidermal pits. These are S shaped in nature. Setae are responsible for locomotion or movement of earthworms from one place to another because setae can be extended or retracted.

Setae are not found in the first, last and clitellum region. That’s why the right answer is: “option D”.

Additional information:
Earthworms are also known as friends of farmers. Because earthworms feed on the waste of crops and other residue and convert them into organic manure. In this way, it increases the fertility of the soil. The process of converting the waste into manure is known as vermicomposting. It also provides better drainage to the soil. That’s why earthworms are considered as the best friend of farmers.
Earthworms are also used as a bait in game fishing. Because earthworms are eaten by fishes. In this way, when earthworms are used in traps, then fishes are trapped in an easy manner.

Note: Setae are the locomotory structures which are found in the middle region of each segment. These are S shaped structures which are retracted and extended. Due to the extended and retracted mode of setae, they are used for movement of earthworms from one place to another.