Giant Sea Fan

Overview

The Giant Sea Fan (Annella mollis) is one of the largest known gorgonian species, forming impressive, fan-shaped colonies that can reach up to 2 meters in diameter. These corals are colonial organisms composed of numerous small polyps that work together to filter nutrients from the surrounding water.

Distribution & habitat

This species is widely distributed throughout the tropical Indo-Pacific, ranging from the Red Sea to the Pacific Ocean. They typically inhabit steep outer reef slopes, drop-offs, and pinnacle reefs where they are exposed to strong currents, though they can also be found in quieter lagoon environments or on shipwrecks.

Appearance

Annella mollis is characterized by its large, regular, fan-like structure that grows in a single plane. The colony consists of thick, smooth, cylindrical branches that often fuse together (anastomose) to create a network of elongated meshes. The overall color of the colony generally ranges from orange-yellow to red.

Biology & behavior

These sea fans are slow-growing, often taking over a decade to reach their maximum size. They possess a tough yet flexible skeleton that allows them to withstand strong water currents by bending and springing back into position. Because of their slow growth rate, it is important for divers to avoid contact with these fragile colonies. They are also known to host various commensal organisms, such as small fish and invertebrates, which find shelter among their branches.

Feeding

As passive suspension feeders, they extend their polyps into the current to capture microplankton and other small organic particles drifting in the water column.