Sunday, June 10, 2007

Coral Spawning

Corals are animals in the phylum Cnidaria. An individual coral build by billions of tiny polyps which produce calcium carbonate skeletons also known as reef building corals or hermatypic corals. Whereas nearly all the soft corals lack of hard skeletons called non-reef building corals or ahermatypic corals.

Nearly all the hermatypic corals have Zooxanthellae - symbiotic algae live in the coral tissue, play important function to enable coral to deposit calcium carbonate much faster and also provide food to the coral polyps.

Corals growth and reproduce by sexually and asexually. The colony grows as the polyps repoduce and also polyps divide to form new polyps. Corals reproduce eggs and sperm just like other animals.
Usually the corals spawn at the night time. When the night falls, coral polyps start to expand and pink coloured bundles are held under the mouth of the polyps are visible through the transparent tissues and waiting for the time to release. When the biological clock stikes, the eggs and sperm released into water in bundles from the mouth of the coral polyps and float to the surface and get fertilize. Fertilized planktonic coral larvae called planula, drift with current for days and reach a suitable habitat to settle and growth to form a new reefs.
For mass coral spawning to take place, synchornized by the tidal change, moon and water temperature which is the specific cue to released all the eggs and sperm exactly the same time. However, the exact time of coral spawning still unpredictable. Mass spawning overwhelms the predator such as huge plankton feeder - whale sharks and other fishes. Besides, mass spawning also important to increase the opportunities of fertilization.
During this early of June, few days after the full moon, there are 4 Japanese divers who was lucky to experienced the unpredictable dive in our house reef here. We saw three species of table coral spawned.
Karasawa Kiyoko san took video of the coral spawning.

Kiuchi Hirotaka san waiting for the coral to spawn.

Akuzawa Hiroaki san took photo of the coral spwaning.

Nagata Kazuyo san observing coral spawning.

1st coral spawned : Acropora cerealis

2nd coral spawned - Acropora listeri

3rd coral spawned - Acropora hyacinthus



Asther said...

Wow... lucky divers! I've encountered barrel sponges spawning once, and it was around 11-ish in the morning. I've seen coral spawning a few times but never lucky enough to have my camera around. :( Hopefully one day I'll b able to capture this wonderful phenomena.

ParadiseLoG said...

Lucky Asther too...
Hope you can share some info about coral spawning with us next time....
Hav a nice day! Look forward to see you soon!