Funky feeding: hydra make a new mouth each time they eat

Hydra are tiny freshwater predators, famed for their regenerative abilities and lack of aging. They anchor themselves to a surface, and stun and kill prey with stinging tentacles, but when it comes to actually eating their victims, things get especially interesting.

Lacking a mouth as such should prove to be quite an obstacle for most. Not so for hydra. Scientists have, for the first time, been able to record the bizarre process by which hydra feed. Once prey has been caught and paralyzed, the hydra contract their tentacles. As they do so the movement essentially rips open its skin to create a gaping maw into which the victim is vacuumed. The cells involved do not actually move apart to create an opening, instead they actually change shape, stretching in a similar manner to how our pupils dilate. In some cases, the newly-created mouth somehow becomes larger even than the body of the hydra itself. Watch the strange process here

“Evolutionarily, why do these animals have this weird mechanism for feeding? We don’t really have an answer for that yet,” says author Eva-Maria Collins of the University of California.

Bizarre and mysterious, research into the strange characteristics of hydra continues.


Originally published in Biosphere Magazine Issue 16.

Image credit: Carter and Hyland et al/Biophysical Journal 2016.

Carter, J, Hyland, C, Steele, R, & Collins, E-A. (2016) Dynamics of mouth opening in Hydra. Biophysical Journal. DOI:


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