An ascomycete commensal on the gills of Bathynerita naticoidea, the dominant gastropod at Gulf of Mexico hydrocarbon seeps

The discovery of a fungal commensal on the gills of Bathynerita naticoidea, the dominant,gastropod at petroleum seep communities located along the Gul f of Mexico upper continental slope (500-800 m), is reported. Light and ele ctron micrographs revealed filamentous fungi of the class Ascomycetes and u nidentified fungal bodies associated with the gill tissue of each of the 7 freshly collected specimens of B. naticoidea examined. Fungi were found att ached to the surface of the gill cells, intercellularly, within the gill bl ood spaces, enclosed in otherwise empty intracellular vacuoles, and externa l but adjacent to the gill tissue. The exact nature of this fungal associat ion is unknown; the fungi may act to detoxify the hydrocarbons and sulfide compounds of the seep environment, or may be parasites that have infected t he gill tissue. Although chemoautotrophic and methanotrophic bacterial symb ionts have been found previously within the gills of deep-sea (2200-3000 m) hydrothermal vent gastropods, there was no evidence of bacterial symbionts within the gills of B. naticoidea. This is the first report of a fungal as sociation within gastropods endemic to hydrocarbon seep or hydrothermal ven t communities.