The Hydra Blog

Cannibalism in Hydra?

Hydra appears not to be cannibalistic. Hydra polyps of the same species do not consume each other, even when they are starving. One Hydra polyp will sometimes swallow another one when both polyps grab the same bunch of brine shrimp in the laboratory. But the swallowed polyp will eventually be egested unharmed. A paper was published on this topic in 1933 (Pickens, 1933). This question is also answered in a paper published in 1923 (Marshall, 1923). This conclusion may apply, however, only to Hydra of the same species. Dick Campbell has told me that Hydra oligactis will swallow Hydra viridissima, but he can’t remember if they actually consume them.

REFERENCES

Marshall, S. (1923). Observations upon the behavior and structure of Hydra. Quart. J. Microscop. Sci. 67, 593-616.

Pickens, A.L. (1933). Reactions of two Hydras, one of which has been ingested by the other. Biol. Bull. 64, 259-261.

hydrablogger

3 responses to “Cannibalism in Hydra?”

  1. Elliot Chodoff Avatar
    Elliot Chodoff

    I worked in Prof. Lawrence Slobodkin’s hydra lab as an undergraduate at Stony Brook University in the 1970’s. I observed that hydra oligactus would ingest and digest chlorohydra hadleyi in the presence of brine shrimp, expelling only the chlorophyll remnant. It was clearly not accidental while attempting to gram the same brine shrimp.

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    1. hydrablogger Avatar
      hydrablogger

      Interesting! Did this only happen in the presence of brine shrimp?

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      1. Elliot Chodoff Avatar
        Elliot Chodoff

        Yes.

        The h. oligactus would become agitated in the presence of c. hadleyi when brine shrimp were introduced. The same reaction occurred when disassociated cells of c. hadleyi (using ultrasound) were present instead of the complete hydra, implying a biochemical receptor mechanism rather than physical.

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