Microbioerosion on shells of Heleobia australis (Gastropoda: Rissooidea) from lagoa Salgada, Rio de Janeiro State, Brazil

Abstract

Traces of microbioerosion are recorded on microgastropods shells that occur in association with recent stromatolites from lagoa Salgada, Rio de Janeiro State. The high destruction levels produced by microborers on the bioclasts were directly observed through optical and scanning electron microscroscopy. This study goals the identification and description of the bioerosion patterns on microgastropods of the species Heleobia australis (D'Orbigny). The microborings consist of sinuous ramified microborings galeries that were related to the ichnogenera Fascichnus, as well as groups of circular and irregular perforations that remained unidentified. Energy Dispersive X-Ray Spectrometry (EDS) analysis of the dark shells surfaces detected the elements sulfur and iron, both closely tied to the microbial metabolism.