Life Cycle - Natural Environment (5A)

  • Observing corals.
  • Exploring and distinguishing the different types of corals.
  • classification
  • coral
  • polyp
  • tropical

Students compare corals. 


Basic information on corals can be found on the previous lesson. Most coral  are a colony of corals, composed of individual polyps.  Individual polyps live in their own little structures within the main frame of the other corals.  Only corals of the same species share colonies with other corals; although various species of corals can live very close to each other.  Some corals can be found as individual polyps.  Individual polyps usually have larger skeletons. 

The information below corresponds to the samples in Life Cycle - Natural Environment (5A).



BLUE CORAL - Helipora species (blue colored specimen)  
This Indo-Pacific blue coral, Heliopora, is relatively rare.  It has a massive lobed skeleton dissected by cylindrical canals.  The blue tint of the skeleton is masked in life by the brown polyps, and is due to the presence of iron salts.  It is used in jewelry because of its color.


BLACK SEA FAN  - Order Gorgacea (black delicate fan structure)
The main stem is firmly attached to a hard surface by a plate or a tuft of creeping branches.  The stems contain a central strengthening rod, consisting of a horny material (gorgonin).  The short polyps occur all over the branches of the colony being absent only on the main stem.

RED ORGAN PIPE CORAL - Tubipora species (red specimen)
The common name is derived from the parallel rows of tubes making up the calcareous skeleton of the colony.  When the polyps are expanded, the red skeleton may be completely obscured.  Colonies can reach 30 cm or more in diameter.  Found in the Indo-Pacific.


STAGHORN CORAL - Acorpora species (white, long straight specimen)
Another of the fast growing reef builders, staghorn coral forms thickets, sometimes of great size, with a lattice-work of loosely connected branching coral colonies.  Colonies may be yellow, brown or cream color with white tips (where the growth takes place).
Staghorn thickets are found not often seaward of the reef flat, where they may adorn the tops of buttresses at moderate depths.  They are also found forming patch reefs in protected lagoons and shore zones in shallow water connected to other colonies (if at all), and are encrusted with algae, sponges, and tunicates.  Damselfishes frequently stake out their territories in staghorn as well as elkhorn coral.

ELKHORN CORAL - Acorpora species (creamy white, smoother specimen that look like a reindeer's horn)
The fast growing branching colonies of this coral are sometimes 4 meters or more across.  The flattened (or thick and cylindrical) branches are brown to yellow with white tips The white tips are due  to lack of symbiotic algae, the zooxanthellae, in areas of new growth.
Elkhorn coral competes by growing rapidly and by shading or over-topping its neighbors.  It often dominates shallow fore reef zones on windward, wave-swept shores.  It is sometimes toppled by storm surf, but may re-grow from its new positions  (broken fragments regenerate to form new colonies).   This capability  may partially explain its wide distribution.

BRANCHING, BRUSH, OR BROWN STEM CORAL - Madracis (specimen with brown spots with branching tips)
These yellow to cream-colored colonies may be several meters across and are formed of thin delicate branches packed tightly together.  The more massive colonies form gently rounded mounts. 
This coral is found at moderate depths on buttress tops, flanks, and fore reef slopes.  Brittle stars and other invertebrates are often harbored between the branches.  Inner parts of the branches are dead and are encrusted with algae, sponges, and other attached invertebrates.  The brittle branches of the coral are easily damaged by divers and boat anchors.

POCA CORAL - Montipora species white, small polyps, crinkled, some have small red specks on them.
Poca forms flat, leafy colonies which may reach 2 meters or more across.  It often grows in dense masses over reef slopes in the Indo-Pacific.

MUSHROOM CORAL - Fungia species (individual polyp, circular specimen with large septa).
A common species reaching 20 cm in diameter, which is found on reefs and lagoons in the Indo-Pacific.  As adults, all species are free-living, but when young they are often seen in clumps, each polyp attached to the bottom by a stalk.

FLOWER CORAL - Eusmilia species (white, large polyps that give the appearance of being squished).
The branching colonies of this coral are brown, green, or yellow and have one large polyp at the top of each branch.  Colonies form mounds which may be 1 meter or more across.
The polyps are generally retracted during the day, but extend long transparent tentacles for feeding on plankton at night.

LEAF CORAL - Montipora species (slightly green, small holes, flatten).
Leaf corals form flat, leafy colonies which may reach 2 meters or more across.  They often grow in dense masses over reef slopes in the Indo-Pacific.


  1. Discuss the different  corals that you have.  The names are not as important as observing the different characteristics of the corals.  Use the information in the "Background" section to guide your lecture.  
  2. Give students a package of corals.  Provide hand lenses or Swift-GH microscopes to observe the corals in detail.  Students should draw what they see on their lab sheets.  You might want to help students draw the individual polyps by going over the following art instructions.


to make a stem draw disc shape lines down group
each polyp
fill in lines
  1. There may be more than 4 different types of corals that the students have.  If they want to draw more, use the back of the lab sheet.  After they finish drawing their specimens, see if they can match their specimens with the display materials.  
  2. Emphasize with students that there are many types of corals, each with its own characteristics.  Make sure students realize that corals belong to the Animal Kingdom, and that they are invertebrates.

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