Marine Invertebrates of Bermuda

Bermuda Fireworm (Odontosyllis enopla)

By Emily Scott
James B. Wood (Ed)

Abstract Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links 

Bermuda Fireworm, (Odontosyllis enopla)
Photo by Genna Ruzanski


There are many organisms in the marine world that are bioluminescent. In Bermuda, the polychaete annelid Odontosyllis enopla bioluminesces during mating activities that take place every month following the full moon. Three days following a full moon, 57 minutes after sunset, the 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. Therefore, the main focus of this page will be reproduction of Odontosyllis enopla as well as some life history traits of other species of the Odontosyllis genus.


Phylum: Annelida
  Class: Polychaeta
    Order: Aciculata
      Family: Syllidae

The phylum Annelida consists of segmented worms with bilateral symmetry and a true coelom. Class Polychaeta is characterized by parapodia, or bristles, on each segment. Many are colored, and have sensory structures located on the head region. Order Aciculata refers to the bristles present on the Annelid, and Family Syllidae is made up of skinny worms with 3 antennae and uniramous parapodia (Sterrer 1986).


Odontosyllis enopla is commonly found in shallow bays around Bermuda (Sterrer 1986). They live in protected, rocky bottoms and swim to the surface 2 to 3 days after each full moon to spawn (Sterrer 1986). They show a peak in spawning activity during summer months (Huntsman 1948). Huntsman (1948) found that when captured, O. enopla swims to the bottom of the container and creates a webbed tube around it, with the head sticking out of one end. This provides evidence that when not mating, O. enopla lives in a tube like structure on the bottom of the bays.

Other organisms of the genus Odontosyllis occupy similar habitats around the world. Odontosyllis luminosa is found in soft sediment and tropical sea-grass in San Martin and Belize (Gatson and Hall 2000). Like Odontosyllis enopla, they also build mucous tubes (Gatson and Hall 2000). Odontosyllis polycera is found on the bottom of inshore bays in New Zealand, and Odontosyllis hyalina lives in the East Indies (Wilkens and Wolken 1981, Daly 1975).


Odontosyllis enopla can grow up to 35mm long, but the average female is 20mm and the average male is 12mm (Gatson and Hall 2000, Sterrer 1986). They have short, compound setae, and many small teeth in their pharynx (Sterrer 1986). They also have 2 pairs of eyes that are located on the dorsolateral surface of the head (Wilkens and Wolken 1981). The eye lobes have the ability to move, and are light sensitive on optical axes,which are straight lines extending from the front of the eye through the center of the eye (Wolken and Florida 1984). The optical axes are different for each pair of eyes (Wolken and Florida 1984).

The eyes of polychaete annelids can be compared to the eyes of vertebrates and cephalopods as they have also evolved camera like features such as an outward retina, photoreceptor cells, pigment granules, and other features that are equivalent to the lens, iris, and cornea (Wolken and Florida 1984, Wilkens and Wolken 1981). Odontosyllis enopla has a visual pigment in their eyes that are tuned to pick up bioluminescent mating signals which are shed at 504-507nm, a visible green color (Wilkens and Wolken 1981).

The most well known ecological trait of Odontosyllis enopla is their luminescent reproductive activities (Goodrich 1933, Galloway and Welch 1911). There are many marine animals that bioluminesce during feeding, reproduction, and defense activities (Wilkens and Wolken 1981). O. enopla, along with some other polychaete annelids, also displays lunar periodicity in their spawning events. Lunar periodicity is seen in response to the change in light intensity from the sun to light intensity from the stars (Huntsman 1948).

Odontosyllis enopla can be observed spawning 2-5 days after the full moon, 57 minutes after sunset, with a peak on the third night following the full moon during summer months. (Sterrer 1986, Wilkens and Wolken 1981, Markert et al. 1961). Females rise to the surface from the bottom and swim in circles while releasing a bright green bioluminescent substance along the length of the body (Markert et al 1961, Huntsman 1948). Wolken and Florida (1984) have identified this bioluminescent substance as a luciferin system. 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 (Huntsman 1948). When a male recognizes the cues, it emits short bursts of light while swimming towards the females (Markert et al 1961). Usually several males are attracted to one female (Markert et al. 1961). When they meet, the male and female swim around each other in a narrow circle shedding their gametes (Markert et al. 1961). They then return to the bottom where they lose their swimming setae and build new mucous tubes (Fischer and Fischer 1995).

Other Odontosyllis species exhibit similar mating behaviors. Odontosyllis luminosa exhibits virtually the same sequence of events, with the females rising to the surface and releasing a bioluminescent egg sac that the males are attracted to (Gatson and Hall 2000). This glow is visible from 30-50 meters away (Gatson and Hall 2000). Odontosyllis polycera becomes bioluminescent one month prior to spawning (Wilkens and Wolken 1981, Daly 1975).

The only observed predator of Odontosyllis enopla has been the silverside, Atherinomorus stipes, which feeds on the annelids during mating (Gatson and Hall 2000). 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 (Gatson and Hall 2000).

Recent Research

There has been very little recent research on Odontosyllis enopla, so I have focused on research conducted in the past 50 years.

Markert et al. (1961) recorded basic observations of the spawning activities of Odontosyllis enopla. He deduced that the likely reason O. enopla spawns at an exact time every month is that they are stimulated by the 56 minutes of dark after sunset. Tides do not influence the spawning because Bermuda experiences small tides and the organisms have always been observed no matter what the tides or weather are like. Further, Markert et al (1961) found that males are not only stimulated by the bioluminescent display of the female, but also by the beam of a flashlight. However, females are not attracted to the artificial beam of light, and only release their gametes once the males are present.

A few studies have been done on the eye structure of Odontosyllis enopla. Along with the specialized structures for sensing the green wavelengths produced while spawning, Wilkens and Wolken (1981) found that the eye contains rods that are arranged in such a way as to line up with the optical axis, promoting maximum collection of light. This was discovered with the assistance of electroretinograms which were created to respond to light at various wavelengths. It was found that the color sensitivity in O. enopla eyes is ideal for sensing bioluminescent flashes (Wilkens and Wolken 1981, Wolken and Florida 1984).

The most recent research on Odontosyllis enopla was conducted by Fischer and Fischer (1995). They were the first to observe the life cycle of O. enopla. They found that unlike many species that die after reproducing, O. enopla survives and returns to their benthic lifestyle. They also observed a reversible epitoky, with the organism going through a metamorphosis each reproductive cycle that included loss of swimming setae and pigment change. Pigment returned two months after spawning. Fischer and Fischer (1995) also collected 7 juveniles, which did not display anatomical differences from the adults except for a white pigment running down the length of the body and differences in proportion of the head, eyes, antennae, and cirri. They were observed building silk tubes, similar to the adults.

Commercial Importance

There is no known commercial value of Odontosyllis enopla. However, ever since the first recorded glimpse of these organisms by Christopher Columbus in 1492, they have been a great, free, tourist attraction during spawning periods, especially during the summer months (Crawshay 1935). It is not uncommon to see a group as large as 30 or 40 people standing out near Ferry Reach in Bermuda during summer months trying to catch a glimpse of this exciting, psychedelic light show. A number of organizations on the island, including Bermuda Underwater Exploration Institute, advertise glow worm cruises so tourists can observe ‘this illuminated mating ritual’ (

Bermuda Laws

There are currently no Bermuda laws regarding Odontosyllis enopla.

Personal Interest

There are many popular beliefs and superstitions about the moon, and as a child I was always fascinated by stories and fairy tales about them. As I grew older and decided I wanted to study marine biology, I learned that some of these stories probably came from early observations of creatures that display lunar periodicity, such as Odonotosyllis enopla (Korringa 1947).

Along with the fascinating tales about the moon and my imagination as a young child, I have also been interested in bioluminescence since my first night plankton tow. I can recall being amazed when the tour leader patted down the net and it began to glow. I think the most interesting thing is that humans can reproduce these chemicals and their amazing effects in glow sticks and psychedelic light shows, but organisms such as O. enopla or the Palolo worm create them naturally (Korringa 1947).


Crawshay, L.R. 1935. Possible bearing of a luminous syllid on the question of the landfall of Christopher Columbus. Nature. 136:559.

Daly, J.M. 1975. Reversible epitoky in the life history of the polychaete Odontosyllis polycera (Schmarda 1861). J. Mar. Bio. Assoc. U.K. 55:327.

Fischer, A. and Fischer, U. 1995. On the life-style and life-cycle of the luminescent polychaete Odontosyllis enopla (Annelida: Polychaeta). Invert. Bio. 114:236.

Galloway, T.W. and Welch, P.S. 1911. Studies on a phosphorescent Bermudain annelid Odontosyllis enopla Verrill. Trans. Amer. Micro. Soc. 30:13.

Gaston, G.R. and J. Hall. 2000. Lunar periodicity and bioluminescence of swarming Odontosyllis luminosa (Polychaeta: Syllidae) in Belize. Gulf. Car. Res. 12:47.

Goodrich, E. 1933. Notes on Odontosyllis. Quart. J. Micro. Sci. 76:319.

Huntsman, A.G. 1948. Odontosyllis at Bermuda and lunar periodicity. J. Fish. Res. Board Can. 7:363.

Korringa, P. 1947. The moon and periodicity in breeding of marine animals. Eco. Mono. 17:349.

Markert, R.E., Markert, B.J. and Vertrees N.J. 1961. Lunar periodicity in spawning and luminescence of Odontosyllis enopla. Eco. 42:414.

Nature. Accessed on November 12, 2007.

Sterrer, Wolfgang. ed. Marine Fauna and Flora of Bermuda: A Systematic Guide to the \ Identification of Marine Organisms. New York: John Wiley and Sons, 1986.

Wilkens, L.A. and Wolken, J.J. 1981. Electroretinograms from Odontosyllis enopla (Polychaeta; Syllidae): initial observations on the visual system of the bioluminescent fireworm of Bermuda. Mar. Behav. Phys. 8:55.

Wolken, J.J. and Florida, R.G. 1984. The eye structure of the bioluminescent fireworm of Bermuda, Odontosyllis enopla. Bio. Bull. 166:260.


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