Odontosyllis enopla worms have been performing their bioluminescent mating ritual in these islands at least from the beginning of recorded time. Chris Columbus was the first European to sail through the TCI in 1492 and wrote in his logs of the remarkable “fire worms”.
There are many organisms in the marine world that are bioluminescent. Unique to the TCI, the O. enopla worm bioluminesces during mating activities that take place every month following the full moon. Three days following a full moon, 55 minutes after sunset, females rapidly swim to the surface and emit a bright green fluorescent chemical that attracts the males who soon follow. Unfortunately, there has been very little research on their life cycle, other than reproduction (the glowing part).
O. enopla is commonly found in shallow bays around the TCI. They live in protected, sandy bottoms and swim to the surface 3 to 5 days after each full moon to spawn. When not mating, O. enopla lives in a tube like structure on the bottom of the bays.
O. enopla can grow up to 35mm long, but the average female is 20mm and the average male is 12mm. They are worm-like, with 2 pairs of eyes and many small teeth.
So at nearly 55 minutes after Sunset, female worms rise from the bottom and swim in circles on the surface while releasing a bright green bioluminescent substance. A female can glow for up to 8 seconds, and can repeat this process up to 33 times over 12 minutes (or until she attracts a male). When a male recognizes the cues, it emits short bursts of light while swimming towards the females. Usually several males are attracted to one female. When they meet, the males and females swim around each other in a narrow circle shedding their eggs and sperm. They then return to the bottom where they lose their swimming bristles and build new mucous tubes.
The only observed predator of Odontosyllis enopla has been the silverside, which feeds on the worms during mating. However, when collected, the fish had regurgitated and were paralyzed, leading to the conclusion that the bioluminescent substance, if not the worms themselves, are toxic.