Question

Movement of coelomic fluid helps in the locomotion of
(a) Hydra
(b) Frog
(c) Starfish
(d) Earthworm

Answer 1

Hint: Different organisms have different organs and mechanisms for their locomotion. Most of the animals use muscles and skeleton to carry out locomotion. In some cases, the coelomic fluid helps in it by keeping the tract moistened.

Complete answer:
In the case of earthworms, the movement of coelomic fluid helps in locomotion. This movement includes contraction and relaxation. This is known as peristalsis. They have bristle-like structures on their body called seta. With these, they use longitudinal and circular muscles that help their body to contract and move forward. The coelomic fluid assists in it. The septa isolate each segment, keeping the fluid. This allows fine-tuned movement.
So, the correct answer is ‘Earthworm’.

Additional Information: The earthworm travels underground. The secretion of mucus aids in the burrowing process in the ground, therefore they make gurgling noise underground when they move through the lubricated tunnel. They move by peristalsis i.e. alternative lengthening and shortening of the body. They anchored to the surrounding by the shortened part with the help of clawlike tiny bristles that are present all along its segmented length. They move through the tunnel in the soil by expanding crevices with the force which is measured according to body weight. The hatchlings have the ability to push 500 times their body weight whereas adults push only 10 times their body weight.
Let us look at the Locomotion process of the other organisms mentioned in the question:
Hydra: Generally, they stick to a suitable object in the water by the basal disk. It twists and makes various movements by tentacles and body, staying fixed in that position. They normally move to capture food and in response to various stimuli. These movements are the result of contraction and expansion of the contractile muscle fibers.
Frog: Frogs generally move with the help of their powerful hind legs, be it leaping or swimming. First, the extensor muscle of the thigh contracts and extends the limb. Then the foot thrusts against the surface and leaps forward. It is transmitted through the body of the frog by the pelvic girdle and the spline, making the whole animal push forward. In the case of swimming the webbed hind legs provide great surface area to push backward.
Starfish: These organisms move by using a water vascular system. Water enters via the madreporite and circulates from the stone canal to the ring canal and into the radial canals. The water is carried to the ampullae by the radial canal and provides suction to the tube feet. Then they latch on the surface and move in a wave. During this one body section stays attached to the surface as the other releases.

Note: Hydra and frog generally use muscular movement. Hydra uses contractile muscle fibers and the frog uses muscles of the thigh and hind legs. In the case of starfish, they use a water vascular system. The coelomic fluid has a role in locomotion only in the case of earthworm. The coelomic fluid helps the organism in the maintenance of moisture in activities such as respiration and burrowing activities.