Black Sun Coral

Overview

The Black Sun Coral (Tubastraea micranthus) is a distinct, non-photosynthetic stony coral known for its dark green to black, tree-like branching colonies. Unlike many other reef corals, it does not rely on symbiotic algae for energy, allowing it to thrive in shaded or deeper environments where light is limited.

Distribution & habitat

This species is native to the Indo-Pacific region, ranging from the Red Sea and East Africa to the Pacific islands. It typically inhabits low-light areas such as caves, overhangs, and deep crevices, though it is also known to colonize artificial structures like shipwrecks and oil platforms. It has been introduced to the Caribbean, where it is considered potentially invasive.

Appearance

Tubastraea micranthus is unique within its genus for its dendroid, or branching, growth form, which can reach up to one meter in diameter. Its thick branches are covered in polyps that are generally dark green to black, often featuring fluorescent green tentacles and mouths. When fully extended, the polyps give the colony a dense, bushy appearance.

Biology & behavior

As an azooxanthellate coral, this species lacks the symbiotic zooxanthellae found in most reef-building corals. It is highly adapted to environments with strong water currents, which help deliver the planktonic prey it requires for survival. It is considered a "voracious" feeder, with polyps that remain extended for longer periods than those of related species to maximize capture opportunities.

Reproduction

This coral reproduces both sexually and asexually. Asexual reproduction occurs through budding from the base or oral disk, allowing the colony to expand. Sexual reproduction involves the release of gametes into the water column, leading to the development of larvae that eventually settle on suitable substrates.