Sclerite formation in the hydrothermal-vent "scaly-foot" gastropod — possible control of iron sulfide biomineralization by the animal
A gastropod from a deep-sea hydrothermal field at the Rodriguez triple junction, Indian Ocean, has scale-shaped structures, called sclerites, mineralized with iron sulfides on its foot. No other organisms are known to produce a skeleton consisting of iron sulfides. To investigate whether iron sulfide mineralization is mediated by the gastropod for the function of the sclerites, we performed a detailed physical and chemical characterization. Nanostructural characterization of the iron sulfide sclerites reveals that the iron sulfide minerals pyrite (FeS2) and greigite (Fe3S4) form with unique crystal habits inside and outside of the organic matrix, respectively. The magnetic properties of the sclerites, which are mostly consistent with those predicted from their nanostructual features, are not optimized for magnetoreception and instead support use of the magnetic minerals as structural elements. The mechanical performance of the sclerites is superior to that of other biominerals used in the vent environment for predation as well as protection from predation. These characteristics, as well as the co-occurrence of brachyuran crabs, support the inference that the mineralization of iron sulfides might be controlled by the gastropod to harden the sclerites for protection from predators. Sulfur and iron isotopic analyses indicate that sulfur and iron in the sclerites originate from hydrothermal fluids rather than from bacterial metabolites, and that iron supply is unlikely to be regulated by the gastropod for iron sulfide mineralization. We propose that the gastropod may control iron sulfide mineralization by modulating the internal concentrations of reduced sulfur compounds.
Additional InformationAuthor postprint. Published version -- © 2006 Elsevier B.V. Received 24 March 2005; revised 23 August 2005; accepted 22 November 2005. Editor: E. Boyle. Available online 10 January 2006. We thank the captains and crews of the R/V Yokosuka and the DSV Shinkai 6500 operation group for their technical expertise. Comments from Stefan Bengtson, Anders Waren, Greg Druschel, Lev Neretin, Hidetoshi Urakawa, Jill Banfield, Mihaly Posfai, Rafal Dunin-Borkowski, Danielle Fortin, Shigeru Kuratani and Horst Felbeck significantly improved our manuscript. We acknowledge Shanna Goffredi for providing us sclerites for magnetic studies. The electron microscopy studies were mostly performed in the Electron Microbeam Analysis Facility of the Department of Earth and Planetary Science, the University of Tokyo. We thank Yozo Hamano of the University of Tokyo for use of the vibrating sample magnetometer for thermomagnetic analyses. REK was supported by a NSF Graduate Research Fellowship. Supplementary materials -- 1 document, 3 QuickTime movies.
Accepted Version - Suzuki2006-greigitegastropod.pdf
Supplemental Material - SUZepsl06Video1.mov
Supplemental Material - SUZepsl06Video2.mov
Supplemental Material - SUZepsl06Video3.mov
Supplemental Material - SUZepsl06supp.pdf