Orange Fire Worm

Overview

The Orange Fire Worm (Eurythoe complanata) is a segmented marine polychaete known for its vibrant coloration and defensive capabilities. While historically considered a cosmopolitan species, recent research suggests it may represent a complex of closely related species found in warm, tropical, and subtropical waters.

Appearance

This worm features an elongate, flattened body that is typically twice as wide as it is high. Its coloration is highly variable, ranging from shades of orange, salmon pink, and red to gray, green, or black, often with a dark midventral line. The species is easily identified by its bright red, tufted gills (branchiae) and prominent white, bristle-like appendages (chaetae) extending from its sides. These hollow, harpoon-like bristles contain a neurotoxin that can cause a painful stinging sensation upon contact.

Biology & Behavior

Primarily nocturnal, these worms remain hidden during the day to avoid predation and desiccation. They typically shelter under rocks, within coral crevices, or buried in soft sediments. When threatened, they may curl into a ball to maximize the exposure of their defensive bristles. They are capable of both sexual and asexual reproduction, the latter occurring through regeneration.

Feeding

Eurythoe complanata is an opportunistic carnivore and scavenger. It uses chemosensory organs to locate food, which includes sponges, soft corals, mollusks, small polychaetes, and barnacles, as well as carrion and detritus. It feeds using eversible mouthparts that can expand to ingest prey.