Generations of scientists, including myself, have observed under the microscope the ability of the giant amoeba Hydramoeba hydroxena to devour Hydra alive by extracting one epidermal cell at a time. This routine activity includes extracting solitary nematocyst cells without triggering discharge.

Is this ability related in some way to Hydramoeba hydroxena possessing a solitary large highly active contractile vacuole. For instance could the pressure difference achieved by the contractile vacuole be powerful enough to pop out a single epidermal cell of the prey?

If this is plausible, then perhaps this giant amoeba merits attention to help shed light on how target cells in mammalian tissues might be extracted one at a time.

Hydramoeba hydroxena has a cosmopolitan distribution in the northern hemisphere and is fairly common amidst wild populations of Hydra attenuata, H. oligactis, H. graysoni, H. circumcincta and Chlorohydra viridissima in ponds and clean streams near Manchester and the Lake District in NW England. This amoeba species is easily cultured in the laboratory in the presence of live Hydra prey, in turn fed by live food such as Daphnia.