Cnida discharge and the mechanism of venom delivery in Anemonia viridis (Cnidaria,Actiniaria)

Cnida discharge in the actinian Anemonia starts with the extrusion of the capsule from the cnidocyte followed by the eversion of the tubule. As the tubule everts, it maintains a tightly closed tip until fully everted. This is considered to be essential for a capsule to discharge as a result of an increase in intracapsular pressure. Venom volumes were measured in 3 types of nematocyst: 408 µm³, 98 µm³, and 9 µm³. Venom flow rates were estimated to range from >43 to 324 µm³ s^–1. It is suggested that the intracapsular pressures required for these flow rates range from 9.7 × 10⁵ to 1.9 x 10⁶ Pa.