Water Excretion by Hydra

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Science  12 Jan 1973:
Vol. 179, Issue 4069, pp. 194-195
DOI: 10.1126/science.179.4069.194


Hydra were cut so that regenerates consisting only of the central gastric region were formed. This region, which has no natural opening to the environment, is capable of osmoregulation and of removing excess fluid from the gut. The fluid is excreted through a break in the body wall created as a result of a strong contraction when the gut is distended with fluid. A normal hydra, therefore, must remove excess fluid by contracting and expelling it through its mouth.

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