nematocyst discharge

The discharge of a nematocyst.

In cnidarians such as jellyfish, a nematocyst is a tiny fluid-filled sac containing a coiled hollow thread that can be shot out at prey.


A nematocyst forms part of a thread cell (nematoblast) in the ectoderm of the animal. When a "trigger" (cnidocil) on the thread cell is touched, the thread is rapidly projected to coil round the prey or inject poison.


The poisonous stings on the tentacles of jellyfish derive from thread cells and their nematocysts.