No abstract

The bearded fireworm, Hermodice carunculata (Polychaeta: Amphinomidae), owes its common name to the tufts of white, sharp, and venomous chaetae (Fig. 1) that, when touched, cause a painful burning sensation (Kicklighter and Hay 2006). In recent years, it has rapidly increased in abundance in Mediterranean infralittoral rocky habitats. In particular, H. carunculata was not common along Apulian coast (Central Mediterranean Sea) until the last decade, and it is indeed missing from lists of polychaete species found in this area published in the early 2000s (see Corriero et al. 2004). Currently, fishermen and scuba divers commonly observe tens of fireworms, 10-30 cm long, crawling on the bottom at the end of summer (approximate density 0.2-1 ind. m À2 , see Video S1). H. carunculata is a well-known generalist predator/scavenger in Western Atlantic coral reef ecosystems (Wolf et al. 2014; Barroso et al. 2015), FIG. 1. Close-up of a bearded fireworm (Hermodice carunculata) feeding on a live sea urchin (Paracentrotus lividus) in coralline barrens. The remains of a sea urchin after predation by fireworms are visible in the background.

The amphinomid fireworm Hermodice carunculata is a potentially invasive species reported throughout the subtropical Atlantic Ocean and the Mediterranean Sea, which is known as a generalist predator and opportunistic feeder. The ongoing climate changes and seawater warming may favour fireworm poleward range expansions and density increases. Our results provide the first investigation into a population which has purportedly been spreading widely in the Salento Peninsula (Apulia, Italy). The specimens were analysed using allometric variables and molecular markers. The best morphometric parameters to estimate individual size were determined as key information for future studies on fireworm population dynamics. To phylogeographically characterize the Apulian population, sequences of the mitochondrial COI and 16S rDNA regions were obtained from a pool of individuals and treated together with those of Atlantic specimens retrieved from GenBank. The estimates of genetic variability for Apulian population were consistent with those recently reported in the literature. Inferences on demographic history analysis confirmed a recent expansion event in Apulia, as has been recounted by fishermen and scuba divers during recent years. Overall, these results constitute a crucial step in the characterization of present-day H. carunculata populations, and provide greater insight into fireworm population ecology.