A Sponge‐Eating Worm from Bermuda: Branchiosyllis oculata (Polychaeta, Syllidae)*,†

Abstract

Abstract. Branchiosyllis oculata is a small, errant polychaete that lives only on the surface of sponges: among inshore Bermudian sponges, 9 out of 16 species surveyed were infested. All of these sponges were conspicuously colored, but the bodies and gut contents of associated polychaetes matched the sponge color only for Tedania ignis (red), Cinachyra alloclada (yellow) and Sphecio‐spongia othella (brownish‐black). For the remaining 6 sponge species, the polychaete bodies were uncolored and the polychaete gut contents were inconspicuously brown or grey. Uncolored polychaetes with grey gut contents were removed from a dark green Tethya actinia and placed on a red Tedania ignis: 2 days later, the polychaete gut contents were red, although the tissues were still uncolored. Acetone extractions of Tedania ignis and Cinachyra alloclada were prepared from sponge tissue and from the gut‐free tissue of their respective polychaetes: absorption spectra matched for each sponge/polychaete pair. To test the influence of ingested sponge pigments on polychaete body color, red polychaetes from Tedania ignis were induced to autotomize their posterior ends, transplanted to other sponge species and allowed to regenerate new posterior segments for 20 days. At the end of the experiment the original segments were still red, but the regenerated ones were either yellow (for polychaetes transplanted onto Cinachyra alloclada, on which resident worms are yellow) or colorless (for polychaetes transplanted onto Chondrilla nucula or Tethya actinia, on which resident worms are uncolored). The foregoing observations suggest that (1) the polychaetes consume the soft parts of the sponges on which they live and (2) the pigments vary among sponge species: pigments from some sponges are stored in the polychaete body, while pigments from other sponges are not. Additional information on the morphology, distribution and natural history of Branchiosyllis oculata is presented and discussed.