Stenotile is the largest of the four types of nematocysts of Hydra. Its capsule is filled with a poisonous liquid called hypnotoxin. Its butt is fat. The butt has three large spines. It’s called a barb. Butt has three rows of barbules.
Work of stenotil or penetrant
(i) It paralyzes prey with hypnotoxin.
(ii) Its trigger grips the prey.