Chemoautotrophic Symbiosis in a Hydrothermal Vent Gastropod

Abstract

An undescribed gastropod species collected from recently discovered deep-sea hydrothermal vents in the western Pacific contains endosymbiotic bacteria within specialized gill cells. The snails inhabit rocky vent openings where they are exposed directly to warm (2-25°C) sulfide-rich (750 µM) water emitted from the vents. The gills of this snail contain elemental sulfur and high activities of enzymes catalyzing sulfide metabolism (sulfide oxidase, ATP-sulfurylase, APS-reductase, rhodanese) and autotrophic CO2 fixation (ribulose bisphosphate carboxylase) indicating that the bacteria function as sulfur oxidizing Chemoautotrophic endosymbionts—a symbiosis described previously only in vestimentiferan and pogonophoran tubeworms, oligocheate worms, and bivalve molluscs. This represents the first documentation of Chemoautotrophic potential among the numerous gastropod species found inhabiting the interface of reducing and oxidizing environments.