Question

Hydra sometimes moves upon its tentacles, using them as legs. This is known as

• A. Somersaulting
• B. Gliding
• C. Walking
• D. Looping

Answer 1

Answer: (C)

Walking

• The movement of Hydra with the help of legs is called as walking. Chemical irritants or prodding the hydra will cause it to contract and then expand again in a slightly different, though random direction.
• If the noxious stimulus persists then it will move by looping, the body is extended and bent over to one side so that the mouth end touches the substrate, the tentacles adhere by discharging a specific type of nematocyst (glutinant) and then the base detaches and is drawn up toward the mouth and reattached.
• This looping may repeat and appears to be in a random direction. During looping the basal end may reattach behind the mouth, or off to the side beside the mouth, or it may loop around 180 degrees and be positioned in front of the mouth (somersaulting).
• A Hydra can move up a glass wall in this way. Locomotion also occurs when the Hydra is not acquiring sufficient food.