MOVEMENTS IN HYDRA AND EARTHWORM

Movements in Hydra 

1) Swaying

Sometimes Hydra comes to rest on rock or other suitable hard surface in water and fixes itself temporarily with mucus substances at the basal disc. Even when Hydra is fixed, it is continuously swaying and this swaying is brought about by the contraction and elongation of the muscles on the sides of the body and tentacles.

 

2) Swimming

Hydra is capable of swimming. This is brought about by the undulating movement of the tentacles.

 

3) Gliding

Alternate contraction and elongation of the muscles of the basal disc results in a gliding movement of the animal.

 

4) Looping

In looping, the animal bends until its tentacles touch the surface of the substratum, that is its body is in the shape of a loop. The foot releases its hold and moves towards the anchored tentacles. Next, the tentacles release their grip and in this way the animal moves forward.

 

5) Somersaulting

Sometimes instead of Hydra moving the base towards the attached tentacles, the base is swung right over and beyond the tentacles to achieve a grip on the other side of the tentacles. This is the somersaulting method of locomotion and carries Hydra faster.

 

Movement in earthworm

Crawling

Animals lacking tails, limbs and fins adopt crawling movement. Earthworms, snails and snakes crawl.

The earthworm moves by crawling. It takes place in a stationary worm as follows:-

The circular muscles of a few of the anterior segments contract. The region becomes narrow and extends forward. The chaetae in this region are withdrawn. This allows the forward extension of the anterior segments. The anterior chaetae are protruded. Following the protrusion of anterior chaetae, the longitudinal muscles contract to pull up the posterior parts.

This contraction of the circular and longitudinal muscles pass posteriorly down the body of the earthworm. The alternate waves of contraction circular and longitudinal muscles with the withdrawal and protrusion of the chaetae result in the forward movement of the earthworm. The contraction of the circular and longitudinal muscles is co-ordinated by the nervous system.