Colonization of a ‘‘Lost World’’: encrustation patterns in modern subtropical brachiopod assemblages

The encrustation of Paleozoic rhynchonelliform brachio-pods has been studied for decades, but modern brachiopods have not received similar scrutiny. The discovery of abun-dant subtropical brachiopods from the Southeast Brazilian Bight provides an unprecedented opportunity to assess epi-biont abundance, diversity, and encrustation patterns in modern brachiopod assemblages. Across the outer shelf, en-crustation frequencies vary among taxa, from mean values of 0.45 % for Platidia to 9.3 % for Argyrotheca. Encrustation frequencies for Bouchardia increase from 1.6 % on the outer shelf to 84 % on the inner shelf. Larger valves are encrusted more frequently, and epibionts preferentially colonize valve interiors. Increased encrustation on the inner shelf may re-flect the greater surface area of larger hosts, longer exposure of dead shells, water-mass characteristics, sedimentation rates, productivity, or other factors that vary with depth. In-ner-shelf brachiopods exhibit encrustation frequencies com-parable to those reported for epifaunal bivalves. The epi-biont fauna is dominated by bryozoans and serpulids, with minor roles played by spirorbids, bivalves, barnacles, fora-minifera, algae, and other taxa. Epibiont abundance at each site is highly variable, but sites are similar in rank im-portance of epibiont taxa. A different suite of epibionts col-onized Paleozoic brachiopods, but similar patterns of en-crustation have been observed, including preferential settle-ment according to valve morphology. These results provide a baseline for evaluating the encrustation of modern bi-valves and ancient brachiopods, and may elucidate the macroevolutionary history of epibionts and their relation-ship to their hosts