Deep in a Japanese Sea Cave at 385 Meters, a Mysterious Green Light Revealed a Creature Never Seen Before

Key Points:

• Scientists have discovered a new species of bioluminescent coral, Corallizoanthus aureus, in a deep limestone cave 385 meters below the ocean near Minamidaito Island, Japan, which emits a green light only when physically touched.
• The coral, belonging to the order Zoantharia, lives exclusively on Pleurocorallium corals and produces light through an intrinsic biochemical pathway likely involving coelenterazine, without fluorescent proteins or symbiotic bacteria.
• The bioluminescence is localized to the coral’s tentacles and is hypothesized to serve as a biological alarm system that attracts predators to deter attackers, supporting the burglar alarm hypothesis in a deep-sea cave environment.
• This discovery marks the first documented case of bioluminescence within a deep-sea cave ecosystem, highlighting the unique adaptations of organisms in permanently dark, nutrient-limited habitats.
• The use of a remotely operated vehicle to explore submerged karst caves around Minamidaito Island showcases the potential for uncovering new marine biodiversity in previously inaccessible underwater geological formations.