Question

Earthworm moves with the help of
(a) Muscles
(b) Setae
(c) Parapodia
(d) Muscles and Setae

Answer 1

Hint: Earthworms belong to the phylum Annelida and are a terrestrial invertebrate. Earthworms move by crawling, taking long strides. This helps them in moving faster on land. Higher animals use muscles for movement. Earthworms have a dedicated system that also includes spiny structures for movement.

Complete step by step answer:
These long strides of earthworms are possible using circular and longitudinal muscles, as well as bristles called setae. An earthworm moves by using two sets of muscles. Circular muscles loop around each of the segments while the longitudinal muscles run along the entire length of the body. When the circular muscles contract, the earthworm stretches its body, becoming longer and thinner. The earthworms keep the setae retracted and push them out of their body when necessary to grab the soil around them. The worm uses its seat as an anchor for the front of its body and then contracts its longitudinal muscles to shorten its body which results in a curve in its body while the back has moved forward.
- The worm then anchors the back of its body with its setae while contracting the circular muscles to lengthen its body. - All of this results in a forward movement of the earthworm. - Thus a combination of muscles and hard spiny setae together form the locomotory apparatus of an earthworm.

Additional Information:
- These seats are present in all the body segments except the first, last, and clitellum.
- There is a ring of these S- shaped seats that are embedded in the epidermal pit of each segment.
- The whole burrowing and locomotion process is aided by the secretion of lubricating mucus which makes the movement through soil easier.
- Earthworms also move through crevices pushing more than 10 times their weight using the muscles.
So, the correct answer is, ‘Both Muscles and Setae’.

Note: This kind of locomotion by setae are not unique to earthworms but is a feature of the phylum Annelida. They lack appendages or parapodia and hence use their muscles and the spiny seat for movement.