Cnidaria · cnidarians

Northern star coral

Astrangia poculata

Rhizangiidae · star coralsIUCN: Least Concern

A small stony coral that lives as far north as Massachusetts and can live with or without symbiotic algae.

Fun factBiologists study it to learn how corals survive bleaching.

Waters
Northeast US, Northwest Atlantic
Depth zone
Coastal shallows & estuaries, Continental shelf
Diet
Plankton & symbiotic algae
Size
Colonies up to 15 cm

Classification

Cnidaria › Anthozoa › Scleractinia › Rhizangiidae

  1. Kingdom Animalia animals
    • Many-celled organisms that eat other living things for energy (heterotrophs)
    • Cells have no cell walls
    • Most can move at some stage of life
  2. Phylum Cnidaria cnidarians
    • Radially symmetric bodies with one opening that is both mouth and anus
    • Stinging cells (cnidocytes) fire tiny harpoons (nematocysts)
    • Two body forms: an attached polyp and a swimming bell (medusa)
  3. Class Anthozoa corals & anemones
    • Live only as polyps; there is no swimming jellyfish stage
    • Gut is divided by internal walls (mesenteries)
    • Includes corals and sea anemones
  4. Subclass Hexacorallia stony corals & anemones
    • Tentacles and internal walls come in multiples of six
    • Includes stony corals and sea anemones
  5. Order Scleractinia stony corals
    • Polyps build a hard limestone skeleton (calcium carbonate)
    • Many reef species host algae (zooxanthellae) that feed them through photosynthesis
    • Main builders of coral reefs
  6. Family Rhizangiidae star corals
    • Small, cool-water stony corals with separate cup-shaped polyps
    • Can live with or without symbiotic algae
  7. Genus Astrangia
    • Species in the same genus are very close relatives and often look alike.
  8. Species Astrangia poculata Northern star coral

Closest relatives in the guide