Polydorids (family Spionidae) are marine annelids that mostly bore into and occupy a variety of calcareous substrates, including mollusc shells and coralline algae. Here we evaluated the identity of polydorids inhabiting coralline algae encrustations of shells of Conus species (family Conidae) from French Polynesia through analyses of sequences of a region of the mitochondrial 16S gene. We observed polydorids in samples of 18 specimens of six Conus species from three locations in French Polynesia. We obtained sequences of 138 polydorid specimens, which represented seven distinct haplotypes. Although it is unclear whether the distinct sequences represent intraspecific variation, they are most similar to a GenBank sequence of Dipolydora armata. For 12 of the 14 Conus specimens for which multiple polydorid individuals were sequenced, we recovered identical haplotype sequences; two haplotype sequences were obtained from the other three Conus specimens, but one of the haplotypes predominated the samples. Moreover, no particular polydorid haplotype showed any obvious association with any of the Conus species. These results suggest that the polydorids inhabiting the encrustations on cone snails of French Polynesia are D. armata or represent close relatives of this species and that communities of polydorids on individual snails are genetically homogenous and possibly established from settlement of few larvae and asexual reproduction of recruits.
Hassig et al. (2026) studied this question.