Nematocyst Inactivation During Feeding in Hydra Littoralis

Hydra littoralis uses stenotele nematocysts for prey-killing. Unused stenoteles are retained when prey-killing ceases. This inactivation results from an accumulation of soluble factors in the surrounding medium, and ends when hydra are placed in fresh culture solution. The inactivation factors are most probably released from the hydra during nematocyst discharge since stenotele activity is reduced by KCl solutions containing nematocyst factors and is enhanced by prey homogenate.