Bubble Coral

Overview

Plerogyra sinuosa, commonly known as the bubble coral, is a distinctive large-polyp stony (LPS) coral recognized for its unique, grape-like vesicles. This species exhibits a fascinating daily transformation, inflating its tissue during the day to maximize photosynthesis and retracting it at night to reveal feeding tentacles.

Distribution & habitat

This species is widely distributed across the Indo-Pacific region, including the Red Sea, the Indian Ocean, and the tropical Pacific. It typically inhabits sheltered reef environments, often favoring turbid waters, crevices, and shaded overhangs where it can grow on vertical surfaces or protected reef slopes.

Appearance

During the day, the colony is covered in fluid-filled, translucent vesicles that can range in color from cream and white to green, tan, or bluish-grey. These bubbles, which typically measure 1–3 cm in diameter, hide a flabello-meandroid skeleton characterized by sharp, prominent septa. When the vesicles deflate, the underlying skeletal structure and the coral's tapered tentacles become visible.

Biology & behavior

Plerogyra sinuosa relies on a symbiotic relationship with zooxanthellae, which reside within its tissues and provide nourishment through photosynthesis. The coral is known to be somewhat aggressive toward neighbors; at night, it extends long, specialized "sweeper" tentacles armed with stinging cells to defend its space and compete for resources.

Feeding

While it derives significant energy from its symbiotic algae, the bubble coral is an active feeder. After dark, once the daytime bubbles retract, the coral extends its feeding tentacles to capture small planktonic organisms from the water column.