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Thursday, August 28, 2008

Now we're gonna talk about sexual reproduction in corals.

1. Corals reproduce sexually by either internal or external fertilization. The reproductive cells are borne on mesenteries (membranes) that radiate inward from the layer of tissue that lines the stomach cavity.

a. Internally fertilized eggs are brooded by the polyp for days to weeks. Free-swimming larvae are released into the water and settle within hours.

b. Externally fertilized eggs develop while adrift. After a few days, fertilized eggs develop into free-swimming larvae. Larvae settle within hours to days.
2. Some corals are hermaphroditic (having both male and female reproductive cells). Others are either male or female. Both sexes can occur in a colony, or a colony may consist of individuals of the same sex.

3. Synchronous spawning occurs in many corals. Polyps release eggs and sperm into the water at the same time. This spawning method disperses eggs over a larger area. Synchronous spawning depends on four factors: time of the year, water temperature, and tidal and lunar cycles.

a. Spawning is most successful when there is little variation between high and low tides. The less water movement over the reef, the better the chance that an egg will be fertilized.

b. At least one-third of the reef-building corals of the Great Barrier Reef are synchronous spawners. These corals spawn (release eggs) annually in the spring. Spawning occurs on the third through sixth nights after a full moon. Larvae usually settle in four to ten days.

4. Once the larva settles on a substrate, it develops into a polyp. Some scientists believe that most larvae settle within 2,000 ft. (600 m) of the parent reef. Others contend that some larvae travel longer distances. Research is ongoing.

we're gonna post another post a short while from now.

see ya till then! :P

KIMBERLEY, THENG HUI , ESTHER.

10:50 PM