Why Coral Is an Animal, Not a Plant

Taxonomy

Corals belong to phylum Cnidaria (class Anthozoa)—same group as jellyfish, sea anemones, hydroids. Animals.

Anatomy & Physiology

• Polyps: Individual animals—cylindrical body, mouth surrounded by tentacles with cnidocytes (stinging cells) for prey capture.
• No photosynthesis: Corals are heterotrophic—they eat zooplankton, dissolved organics.
• Symbiosis: Reef-building corals host zooxanthellae (dinoflagellate algae) in tissues. Algae photosynthesize, providing ~90% of coral's energy. Coral provides CO₂, nutrients, shelter. This partnership ≠ being a plant.
• Skeleton: Polyps secrete calcium carbonate (aragonite) cups—colonial accumulation forms reefs.

Key Animal Traits

• Multicellular, eukaryotic, no cell walls.
• Ingest food (phagocytosis).
• Motile larval stage (planula).
• Nervous system (nerve net).

Corals are colonial animals farming algae—not plants, not rocks.