Phylum:           Cnidaria          Hatschek, 1888

General                                                      

• Greek  “Cnidos” means stinging nettle
• Containing over 9,000 species (MESC 2021)
• Oldest clade of animals with ‘true tissue’
• Includes corals, hydras, jellyfish, Portuguese men-of-war, sea anemones, sea pens, sea ships and sea fans

Distribution

• Around the worlds oceans
• Freshwater and Marine Waters, mostly marine, approximately 20 freshwater species (Hydra)

Habitat

• All Aquatic, mostly marine (MESC 2021)
• Some are Solitary (Sea Anemone), some conical (Corals)
• Sessile (fixed to a substance) or free-swimming

Defining Characteristics

• Mostly radially symmetry, however sea anemones exhibit biradial symmetry, some exceptions eg. blue bottle
• Soft Bodies animals
• Diploblastic animals and show tissue level (grade) of organization
• Presence of cnidoblasts with stinging nematocysts on the tentacles
• Polymorphism and have two body forms, i.e. polyp and medusa
• Made up of 98% water
• Exoskeleton chitinous (perisarc) or calcareous (corals)