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Stinging Beauty

A purple jellyfish
Sergi Garcia, Flickr

Don't let this jellyfish's beauty fool you—even glancing one of their tentacles will cause a dreadful sting. Pelagia noctiluca have tentacles with specialized cells called nematocysts to capture prey.  The nematocysts are organelles within special cells (cnidocytes) that contain venom-bearing harpoons. The cell is activated upon touch or chemical cue, causing the harpoon to shoot out of the cell and spear the prey or enemy, releasing toxin—a process that takes only 700 nanoseconds.