Cnidaria (jellyfish, anemones and corals)

​Cnidarians are fascinating creatures with unique adaptations that allow them to thrive in various marine environments. The phylum Cnidaria includes a diverse group of marine animals known for their stinging cells called cnidocytes. Here are some key groups within this phylum.  Click on each image to enlarge.

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Sea Anemones (Class Anthozoa)

• Characteristics: Polyp form, often attached to surfaces, with tentacles surrounding a central mouth.
• Habitat: Found in coastal waters, often attached to rocks, coral reefs, or other substrates.
• Examples: Giant green anemone (Anthopleura xanthogrammica), Beadlet anemone (Actinia equina).

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Jellyfish (Class Scyphozoa)

• Characteristics: Gelatinous bodies, tentacles with stinging cells, and a bell-shaped structure.
• Habitat: Found in oceans worldwide, from surface waters to deep sea.
• Examples: Moon jellyfish (Aurelia aurita), Lion's mane jellyfish (Cyanea capillata).

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Corals (Class Anthozoa)

• Characteristics: Colonial organisms that build calcium carbonate skeletons, forming coral reefs.
• Habitat: Warm, shallow waters, primarily in tropical regions.
• Examples: Staghorn coral (Acropora cervicornis), Brain coral (Diploria labyrinthiformis).

More about Coral Reefs

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Here are some more for you to explore

Hydroids (Class Hydrozoa)

• Characteristics: Both polyp and medusa forms, often colonial, with specialized individuals for feeding, reproduction, and defense.
• Habitat: Found in a variety of marine environments, from shallow waters to deep sea.
• Examples: Portuguese man o' war (Physalia physalis), Hydra (Hydra vulgaris).

​​Box Jellyfish (Class Cubozoa)

• Characteristics: Cube-shaped bell, highly venomous stings, and complex eyes.
• Habitat: Primarily found in tropical and subtropical waters.
• Examples: Australian box jellyfish (Chironex fleckeri), Irukandji jellyfish (Carukia barnesi).

Sea Pens (Class Anthozoa)

• Characteristics: Colonial organisms resembling quill pens, with a central stalk and polyps extending from it.
• Habitat: Found in soft sediments on the ocean floor, from shallow waters to deep sea.
• Examples: Sea pen (Ptilosarcus gurneyi), Sea whip (Virgularia sp.).

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