Amphinomidae Family of Bristle Worms

One Bristle Worm of  the Amphinomidae Family can be found in this website:

Gulf Fireworm, Eurythoe complanata.  A representative of the Amphionomidae Family of Bristle Worms.

Phylogeny:  Bristle Worms of the Amphinomidae Family are members of the phylum Annelida. They are in the class Polychaeta (which comes from the Greek words meaning “many bristles”) and the order Amphinomida. Amphinomidae is one of two families in this order. The Amphinomidae Family is fairly large, with two subfamilies, twenty-three genera, and one hundred thirty-eight species. They are also known as Amphinomids and in Mexico as Gusanos de Cerdas.

Morphology:  Bristle Worms have bodies that are composed of ringed segments and each of their body segments has a pair of bundled bristles (chaetae) and a pair of foot-like projections. In some species, these “feet” are paddle-like, to assist with swimming, burrowing, and creating a feeding stream. Other than the head and terminal segment, all the segments are identical. Bristle Worms are flattened and oblong or ovate-oblong in shape. The cephalic lobe is rounded or compressed. They have two pairs of eyes, with either both pairs mounted dorsally, or one pair dorsal and one pair ventral. The bristles of most polychaete are made of chitin. The bristles of Amphinomidae Bristle worms however are calcareous. The bristles are hollow and harpoon-like. Some species are known as Fire Worms because when handled they cause a long lasting very painful burning sensation. The bristles of Fire Worms are filled with complanine, an organic molecule that is an ammonium salt. If the spines puncture skin or mucous membrane, they break off and release the complanine, which causes intense burning pain and inflammation. First aid for Fire Worm “burns” include applying vinegar or isopropyl alcohol and removing the spines with tweezers. Many tropical species of Bristle Worms are brightly colored. The Bristle Worms can reach up to 35 cm (13.8 inches) in length.

Distribution:  Bristle Worms are found in a variety of habitats including coral reefs, kelp plants, mud, rock reefs, sea grass beds, sands plains and on floating logs and flotsam. Most are found in shallow waters, but some are found at depths exceeding 365 m (12,000 feet).  They are found worldwide, primarily throughout the tropical and subtropical regions, but some species are found in temperate and even boreal waters. Fourteen species from the Amphinomidae Family are found in Mexican waters.

Reproduction:  Bristle Worms 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.  During sexual reproduction, the males and females swim to the water’s surface. While mating the females displays bioluminescence, either to attract a mate or to repel predators.

Ecosystem Roles:  Amphinomid Worms consume coral polyps, crustaceans, detritus, mollusks, and sponges. Their bristles are highly effect to avoid predation. Mollusks, especially cone shells (Conus sp.), are their primary predators.