Cnidaria (general)

• eg -> jellyfish, corals, sea anemones and hydras
• Cnidocytes (nematocytes) -> specialised cells, used for capturing prey, or defence
• From greek 'cnidos' meaning stinging nettle
• 30 types of cnidae
• Penetrant -> largest and most complex, pierces skin/exoskeleton of prey and injects venomous fluid (hypotozin) which paralyses/kills -> nematocysts
• Glutinant -> sticky surface used to stick to prey (ptycnnocyts)
• Basic form

  
• volvent -> smallest, pear-shaped nematocyst, containing short, thick, spineless, smooth and elastic thread tube when discharged, it tightly coils around prey - spirocysts

  Taxonomical importance
• contain some of the most potent toxins