Population Structure of the Coral-eating Fireworm Hermodice carunculata in the Wider Caribbean, Atlantic and Mediterranean Sea

The bearded fireworm Hermodice carunculata is an important benthic invertebrate scavenger distributed in reefs worldwide. Fireworms are facultative corallivores and have been shown to transfer pathogenic agents between coral colonies. The effects of predation on coral species can be substantial. There is limited data on the genetic population structure of H. carunculata because of its cryptic nature and past studies resulted in ambiguous findings. Both morphological and molecular data suggest the presence of multiple fireworm sibling species but the morphological differences do not reflect the phylogeographic patterns of the species complex.

Hermodice carunculata is an ideal species to use for genetic analysis to infer patterns of population structure and gene flow because of its biphasic life style with planktonic larvae and benthic adults. We collected 412 H. carunculata samples from over 20 locations in the Caribbean, Mediterranean Sea, Gulf of Mexico, Western and Eastern Atlantic Ocean. We sequenced two mitochondrial markers: Cytochrome C Oxidase subunit I (COI) and Cytochrome b (Cytb) from each specimen to examine the genetic diversity of H. carunculata. There is substantial genetic diversity within H. carunculata and preliminary evidence suggests the presence of at least two cryptic species in multiple locations. The presence of multiple species in bearded fireworms indicates our incomplete knowledge in one of the most important invertebrate scavengers in tropical and subtropical reefs.