Pearl Bubble Coral
Plerogyra sinuosa, a jelly-like genus, also known as a Pearl Bubble Coral, Grape Coral, or Tiny Bubble Coral, is a large polyp stony coral. It is usually found in the eastern Indian Ocean, from the Red Sea to Madagascar, and in the Pacific, from Okinawa to the Line Islands.
Bubble corals are stony corals with skeletons just under their fleshy ground, which should not be confused with soft corals or fish eggs. Bubble corals inflate their vesicles during the day to obtain light for photosynthesis, then eject it at dark and hungry tentacles appear. Bubble corals spend all night searching for zooplankton or something else delicious to float by, which they can easily trap and carry along to the polyps’ coral mouths.
Bubble corals can only be found in environmental conditions with little or no flow. Bubble coral skeletons have thin circular teeth that can destroy delicate vesicles if struck or disrupted by the high flow. In sometimes turbid, cloudy weather, aim for bubble corals on walls or overhangs.
On the Bubble Coral, smooth grape-like vesicles up to 2.5 cm (1 inch) in diameter cover a meandering skeleton. Bubble corals may be small colonies with a few dozen vesicles or huge, meandering corallites that span several meters in length. The bubble coral develops a maze-like pattern of thick corallite that grows outwards. On wide colonies, the corallites, and valleys between them are easily visible when polyps are retracted. Bubble reef shrimp and other marine invertebrates can be found within the polyps.