Gulf Fireworm, Eurythoe complanata

Gulf Fireworm, Eurythoe complanata. Fireworms collected within the El Tule Tidal Pools, Baja California Sur, January 2016.

Phylogeny:  The Gulf Fireworm, Eurythoe complanata (Pallas, 1766) is member of the Amphinomidae Family of Bristle Worms and Fireworms. The genus Eurythoe is one of twenty-one genera in this family, and there are sixteen species in this genus. This species is also known as the Iridescent Fire Worm, Cosmopolitan Fireworm, and the Common Fire Worm and in Mexico as gusano fuego común.

NOTE – Some sources state this this fireworm is misidentified and that Eurythoe complanata, though widespread, does not live in the Eastern Pacific. They refer to it as  an unknown species within the genus Eurythoe. Other sources list this species as a subspecies – Eurythoe complanata mexicana (Berkely & Berkeley, 1960). The World Registry of Marine Species (WoRMs) recognizes it as a valid subspecies found in the Eastern Pacific. Most reference, though possibly dated, show it as Eurythoe complanata. Further DNA analysis is required to make this distinction.

Morphology:  The Gulf Fireworm is elongate and flattened, about twice as wide as it is high. The body is composed of multiple segments, each with an appendage (parapodium) on both sides. There are two types of parapodia- straight and serrate or branched and bushy. The head has four eyes and several sensory tentacles. They can be various colors including: orange, salmon pink, blue, greenish, or black. They vary on the length, from 15 cm (5.9 inches) to 1.00 m (3 feet 3 inches) with most species being less than 40 cm (16 inches).

Habitat and Distribution:  Gulf Fireworms are found under rocks on reef flats and sand. They live intertidally, and to a depth of 108 m (354 feet). Gulf Fireworms have a circumtropical distribution. In Mexican waters, this species is found along the Gulf of Mexico, Caribbean, Gulf of California, and Pacific coasts, with the exception of the West coast of the Baja Peninsula north of Todo Santos, Baja California Sur. If this is the subspecies mexicana, it is limited to the Pacific ocean.

Diet:  Gulf Fireworms are nocturnal predators, feeding on sponges, hydroids, coral polyps, and ascidians.

Predators:  Gulf Fireworms have venomous bristles (setae) along their bodies to protect them from many predators, but they are still eaten by fish, crabs and some mollusks.

Reproduction:  Gulf Fireworms are gonochoric (male or female for life). They are able to reproduce both asexually through body fragmentation, and sexually through broadcast spawning. Fertilization is external. The eggs hatch into a planktonic larval form.

Ecosystem Interactions:  Gulf Fireworms  engaging in any types of parasitic, commensal, or symbiotic relationships has not been documented.

Human Interactions:  The setae of Gulf Fireworms can deliver a painful sting to humans. The sting causes a burning sensation, which is the reason for the name Fireworm. Fireworms are unlikely to sting a human unless they are handled or stepped on. Otherwise, Gulf Fireworms have little direct impact on human activities. From a conservation perspective the the Gulf Fireworm has not been formally evaluated however they are common with a very wide distribution and should be consider to be of Least Concern.

Synonyms:  Amphinome complanata, Amphinome jamaicensis, , Amphinome macrotricha, Aphrodita complanata,  Eurythoe albosetosa, Eurythoe alcyonia, Eurythoe assimilis, Eurythoe capensis, Eurythoe corallina, Eurythoe ehlersi, Eurythoe havaica, Eurythoe indica, Eurythoe kamehameha, Eurythoe pacifica, Eurythoe pacifica levukaensis,  Lycaretus neocephalicus, and Pleione alcyonea.