The bearded fireworm is a member of the bristleworm family. Bristleworms all look hairy and many of them are venomous, but this extraordinary species is even hairier than most of its relatives and it was named fireworm after the intense burning sensation it causes with the toxins it releases through its hairs.
Fireworms are quite common in the Mediterranean and in the Caribbean region, and the coastal areas of the Atlantic Ocean also give home to many of these worms. They love warm, shallow waters – therefore, they are found mostly in reef areas, in waters not deeper than 40 m.
Bearded fireworms are quite large, usually between 15 and 30 cm long. They have a flattened and elongated body divided into numerous separate segments, usually 60-150 of them, gills located on the sides, a ventral mouth on the second segment and a head on the first one, with the sensory organs such as the eyes. The hair-like bristles are quite long and they are arranged in clusters on the sides of the body, each bundle being rooted in an organ called parapodia, which is also used for locomotion and breathing. The hairs are hollow inside; therefore, they are quite sensitive and break easily, but they are also the animal’s main weapon used for injecting a venomous chemical into its predator.
Fireworms are varied in terms of coloring – they are actually quite spectacular. Green, red, yellowish and brown fireworms are just as common as white ones. Many individuals are multicolored, with the segments being of one color and the bristles of a different color.
These fireworms are voracious and aggressive. The usually prey on small crustaceans, the polyps of stony corals – Gorgonian corals are their favorites – and anemones, and they also feed on dead animal particles floating in the water. When a fireworm finds a suitably appetizing coral, it climbs to the tip of the branch and takes it in its mouth, wrapping itself around the branch. The worm moves on only when it has sucked all life out of the branch.
Being slow-moving creatures, they have developed a very efficient defense mechanism: they protect themselves by stinging their predators. The long bristles puncture the skin of their enemies and inject a neurotoxin into them to cause a painful, burning feeling, repelling enemies. The bristles can penetrate the human skin, too, causing dizziness, nausea and the burning sensation on the skin where it came into contact with the worm. However, they do not attack deliberately, the bristles flare only when the animal is touched.
Bearded fireworms put on a real show during mating. The females come to the surface of the water and start emitting a fluorescent glow to attract the males. The males respond to the glow by emitting flashing light signals, then they approach the female. Fertilization happens externally -the females release their eggs and the males their sperm into the water, the two types of cells combining to give life to young bearded fireworm individuals.