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CORALS
Reef Scene
courtesy NOAA
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Phylum Cnidarian includes:
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The phylum Cnidaria includes jellyfish, sea anemones, corals, and hydrozoans. These radially symmetric organisms are further divided into two classes: Hydrozoa and Anthozoa.
Fire Coral
courtesy NOAA
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Hydrozoa
- Hydrozoans include fire corals
- Two species of fire coral live in Florida waters
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Milleporina, commonly referred to as fire corals, are hydrozoans. They are common throughout the Caribbean and Atlantic reefs with two species found in Florida waters: Milliporina alcicornis, a branching form, and Milliporina complanta, a bladed form. Fire coral is named for the nematocyst-containing defensive and food capturing polyps. Nematocysts contain a coiled barb, trigger, and neurotoxin. Upon stimulation, the trigger shoots the barb, which releases the neurotoxin upon entering the prey or predator.
Coral Polyps
courtesy Florida Keys National Marine Sanctuary
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Anthozoa
- Anthozoans consist of several subclasses including:
- Octocorallia - soft corals
- Zoantharia - stony corals
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Anthozoans include soft corals, gorgonians, stony corals, and anemones. The subclass Octocorallia consists of the soft corals including gorgonians. On Florida's reefs, soft corals are common in various forms ranging from encrusting mats to large sea fans. Gorgonians, including sea fans, sea plumes, and sea rods, are well-adapted to wave action with flexible skeletal materials and strong holdfasts that attach to the bottom substrate. Zoantharia includes the order Scleractinia, the stony corals. These corals are distinguished by a stony, calcareous skeleton. Each coral polyp is enclosed in a calcium carbonate cup-like structure. These cups are cemented together, forming a coral colony of thousands or millions of polyps.
Stony Coral Skeletons
© Jan Bester
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These polyps are withdrawn during the day, opening up at night to feed on zooplankton. During the day, the symbiotic algae located in the coral tissues, carry out photosynthesis. The algae release some of the compounds produced via photosynthesis to the host, while receiving nutrients from the coral in the form of waste products including ammonia and phosphates. Both symbiont and host benefit in this mutualistic association.
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