EFFECTS OF POLYCHAETE BORINGS ON THE PRESERVATION OF THE BRACHIOPOD BOUCHARDIA ROSEA

Brachiopods have a fossil record extending hundreds of millions of years, and have been important players in marine communities for much of the Phanerozoic. While small marine organisms, they provide a basis for studies on colonization and paleocommunities that can be applied at larger scales, and so benefit our understanding of more complex systems. In this study, 144 of the rhynchonelliform brachiopod Bouchardia rosea were collected from a depth of 15.5 m at Ilha Grande, RJ, Brazil. Dimensional measurements of length, width, and height were collected on the pedicle valves and were found to range from 8mm to 18mm in length, with encrustation data and surface area data gathered as well. By looking at these components, it is possible to determine if there are preferred locations or size classes for sclerobionts colonizing brachiopod shells. While most brachiopods are colonized post-mortem, there is some evidence that not all organisms colonize at this stage, but during the host’s life as well. Repair scars have been interpreted as evidence that spionid polychaetes may colonize living brachiopods and the brachiopods respond by secreting calcite. Because these borings may occur during the host’s life, they may influence the later colonization of the shell. Comparing measurements of the frequency of encrustation of bored versus unbored brachiopods may demonstrate whether previous colonization events deter or encourage the settlement of later colonists.