Bearded fireworms are usually between 5–10 centimetres (1.9–3.9 in) in length, but can reach up to 35 centimetres (13.8 in). They have a group of venomous white bristles on each side, which are flared out when the worm is disturbed.
Bearded fireworms are usually found on reefs, under stones in rocky areas of the sea, and on some mud bottoms. They live throughout the tropical western Atlantic and at Ascension Island in the mid-Atlantic. They can be found near ocean reefs and at depths of up to 150m. They are very common in Caribbean reef systems across the Antilles, where they are often spotted by divers at a wide range of depths. They are also common in the Mediterranean Sea in the coastal waters surrounding Cyprus and the Maltese archipelago.
The bearded fireworm is a voracious predator on soft and hard corals and other cnidarians. It is one of very few animals that feeds on the invasive octocoral Carijoa riisei, the others being the nudibranchs Phyllodesmium poindimiei and Tritoniopsis elegans. The fireworm's red branchiae and white bristles render it well camouflaged when grazing on the octocoral.
Disposition and defences
The bearded fireworm is a slow creature, and is not considered a threat to humans unless touched by a careless swimmer. The bristles, when flared, can penetrate human skin, injecting a powerful neurotoxin and producing intense irritation and a painful burning sensation around the area of contact. The sting can also lead to nausea and dizziness. This sensation lasts up to a few hours, but a painful tingling can continue to be felt around the area of contact. In a case of accidental contact, application and removal of adhesive tape will help remove the spines; applying alcohol to the area will also help alleviate the pain. Cold water and ice soothe the pain of the poison that was injected from the bearded fireworm.