E. complanata’s colloqueial name, the Fireworm or Bristleworm, is indicative of it primary identification characteristic, its spectacular (almost hairy) array of calcareous bristles, protruding laterally from each parapodia. These white, hollow, harpoon-like bristles are spread when the animal feels threatened, with contact resulting in a painful sting, produced by a neurotoxin. When encountered in the wild, they often curled in a ball, allowing maximum bristle exposure. This is when they are most dangerous!

E. complanata exhibits a variety of characteristics that identify it as a member of the polychaete superclass. It possesses segmentation, with paired parapodia and setae for locomotion, a developed prostomium and two pairs of antennae (Ruppert et al, 2004).

Further identification of the E. complanata to the species level is possible through other morphological characteristics. It possesses an elongate, posteriorly tapered, ventrally-flattened body, allowing maneuverability in the confines and crevasses of its preferred benthic habitats (figure 1). As the intraspecific variation dictates, these organisms may vary in colour from an exuberant red and orange to a rather drab grey with red margins (figure 2).



    

Figure 1. E. complanata exhibiting standard identification traits. Note the calcareous setae protruding from each parapodia.

 

Figure 2. Intraspecific variation of morphological characteristics in E. complanata.