Bearded Fireworm in Cozumel

A flattened segmented worm in green-brown and red, fringed along both sides with tufts of white bristles that look soft and are not.

Quick ID

Where You Will See It In Cozumel

Bearded Fireworm works the 6 to 82 foot band. On this island that means the sheltered west-coast reefs, and the shallow east-side entries when the sea is flat — these are the sites where the depth and the habitat line up for it.

Without a boat. It is worth looking for at Chen Rio, Coral Princess and El Islote — all shore entries, so you dive them on your own schedule.

On an ordinary beginner boat dive. It should be within reach at San Clemente, Yellow House, Yucab, Casa Blanca and Chankanaab Bolones. No advanced certification needed.

Deeper, and on the walls. It is also plausible on Villa Blanca Wall, Barracuda Reef, C-53 Wreck and Cantarel (Eagle Ray Wall).

Conditions change the odds more than the site does — the current, the time of day and how much the group has already stirred up the sand. Ask your guide what they have been seeing that week.

Behaviour

Feeds on coral tissue, anemones and dead animals. When threatened it flares the white bristles outward — that flare is the warning.

Commonly Confused With

• Nudibranchs — Nudibranchs have exposed gills but no rows of white bristles along the flanks.
• Flatworms — Flatworms glide smoothly with no bristles or visible segments.

Diving Etiquette And Safety

The white bristles are hollow, venom-bearing and detach into skin on the lightest contact, causing burning pain that can last for days. Never handle one, and be careful where gloves and knees go on a night dive.

Part of the Cozumel marine life guide · see Cozumel dive sites · plan your Cozumel dive trip

Photo: Diego Delso, CC BY-SA 4.0, via Wikimedia Commons.