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Acropora monticulosa, Digitate Stony Coral. Scott W. Michael
Feathery hydroids, capable of delivering a powerful sting. Scott W. Michael
Cassiopeia xamachana, Mangrove Upsidedown Jellyfish. Janine Cairns-Michael
Heteractis magnifica, Magnificent Sea Anemone. Scott W. Michael
Protopalythoa spp., Zoanthids Scott W. Michael

[edit] The Cnidarians

Hydras, Jellyfishes, Sea Anemones, Corals

Number of Living Species: more than 9,000, mostly marine.

Common Characteristics: radial symmetry; a gutlike gastrovascular cavity (coelenteron) with a common mouth/anus; tentacles surrounding the mouth aid in the capture of food; tentacles armed with stinging structures known as nematocysts; two predominant body forms: the sessile polyp, such as the corals, and the free-swimming medusa, such as the jellyfishes.

Noteworthy Behaviors: all are carnivorous, feeding on plankton of various types and sizes; many have symbiotic zooxanthellae embedded in their tissues that provide an important source of energy; some, especially members of the Classes Hydrozoa, Cubozoa, and Scyphozoa, can deliver painful or even fatal stings to humans; those that secrete calcium carbonate (especially the stony corals) are primary contributors to coral reef formation.

[edit] Hydroids

Class Hydrozoa (Hydrozoans, Hydroids, Hydrocorals): 2,700 species

[edit] Jellyfishes

Class Scyphozoa (Jellyfishes): 200 species

[edit] Corals and Anemones

Class Anthozoa (Sea Anemones, Stony Corals, Soft Corals, Zoanthids, Gorgonians, Sea Pens, Sea Pansies): 6,000 species

From: Reef Life by Denise Nielsen Tackett