Information on Hydras 2




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Hydra Behavior

Hydras, like their relatives the jellyfish and sea anemones, have stinging cells with which they capture their prey. Each stinging cell is a rounded cell with a hollow coiled thread inside that shoots out. There are four types of thread, all of which are triggered by touch and chemical reactions. The first thread injects a poison. The second entangles prey, the third is probably defensive, and the fourth is used to fasten the tentacles when the hydra is walking. Hydras stinging cells cannot be used again but are replaced by new ones migrating in from other parts of the body.

When unanchored, hydras use a sliding movement. It can move more rapidly by using a looping movement or a series of somersaults. Hydras can also float at the surface of the water buoyed up by gas bubbles given out by the basal disc.


Their diet consists of water fleas, insect larva, worms, new hatched fishes and tadpoles.


Hydras reproduce both sexually and by budding. Most species reproduce sexually in the autumn or early winter. The amount of carbon dioxide in the water can trigger reproduction. Embryos expel and secrete a sticky shell. After 3-10 weeks, the hydra breaks from its shell, grows tentacles, and becomes a new hydra. New hydras can be formed in buds which form on the side of the parentís body.



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