Extremely fast firing mechanism of sea anemone's stinging cell*

Cnidarians are known for their explosive cnidocyte (stinging cell), used mainly for predation. They use these explosive cells in aqueous environments to capture prey and defend themselves in seemingly unfavorable conditions given the dense medium that imposes a high drag. Moreover, previous studies show that cnidocytes vary in size, shape, and firing mechanisms. Beyond the biology of cnidocytes, the lack of pre-existing research surrounding the harpoon firing apparatus necessitates a kinematic and mechanical analysis. Recently, we have successfully imaged the firing mechanism of a cnidocyte of Nematostella vectensis using micro-high speed videography. The video shows that the firing mechanism utilizes the release of large amounts of strain energy stored in a bent elastic harpoon. To further study the newly identified firing mechanism in a more controlled setting, we experimentally modeled the firing mechanism using bent Nitinol wire. The mechanical model operating at a wide range of Reynolds number were tested.