🪸 Phylum Cnidaria
Jellyfish, Corals, Sea Anemones & Hydrozoans
🔬 What Are Cnidarians?
Phylum Cnidaria (pronounced "ny-DARE-ee-uh") is a diverse group of aquatic animals that includes around 10,000 species. They live predominantly in marine (saltwater) habitats, though a few species, like Hydra, live in freshwater.
Their defining feature is the cnidocyte — a specialized stinging cell containing a tiny harpoon-like structure called a nematocyst, used for capturing prey and for defense.
📌 Key Term: The name "Cnidaria" comes from the Greek word cnidos, meaning "stinging nettle." Every cnidarian has stinging cells!
📋 The Four Classes of Cnidarians
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Anthozoa
Sea anemones, corals, sea pens
Polyp form only🪼
Scyphozoa
"True" jellyfish
Medusa dominant⚠️
Cubozoa
Box jellyfish (highly venomous)
Cube-shaped bell🌿
Hydrozoa
Hydra, Obelia, Portuguese man-of-war
Both forms