Research Article| December 01, 2008 Earthworms produce granules of intricately zoned calcite Martin R. Lee; Martin R. Lee 11Department of Geographical and Earth Sciences, Gregory Building, Lilybank Gardens, University of Glasgow, Glasgow G12 8QQ, UK Search for other works by this author on: GSW Google Scholar Mark E. Hodson; Mark E. Hodson * 22Department of Soil Science, University of Reading, Reading RG6 6DW, UK *E-mail: m.e.hodson@reading.ac.uk Search for other works by this author on: GSW Google Scholar Graham Langworthy Graham Langworthy 22Department of Soil Science, University of Reading, Reading RG6 6DW, UK Search for other works by this author on: GSW Google Scholar Geology (2008) 36 (12): 943–946. https://doi.org/10.1130/G25106A.1 Article history received: 28 May 2008 rev-recd: 07 Aug 2008 accepted: 18 Aug 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Martin R. Lee, Mark E. Hodson, Graham Langworthy; Earthworms produce granules of intricately zoned calcite. Geology 2008;; 36 (12): 943–946. doi: https://doi.org/10.1130/G25106A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Earthworms of the family Lumbricidae, which includes many common species, produce and secrete up to millimeter-sized calcite granules, and the intricate fine-scale zoning of their constituent crystals is unique for a biomineral. Granule calcite is produced by crystallization of amorphous calcium carbonate (ACC) that initially precipitates within the earthworm calciferous glands, then forms protogranules by accretion on quartz grain cores. Crystallization of ACC is mediated by migrating fluid films and is largely complete within 24 h of ACC production and before granules leave the earthworm. Variations in the density of defects formed as a byproduct of trace element incorporation during calcite crystal growth have generated zoning that can be resolved by cathodoluminescence imaging at ultraviolet to blue wavelengths and using the novel technique of scanning electron microscope charge contrast imaging. Mapping of calcite crystal orientations by electron backscatter diffraction reveals an approximate radial fabric to the granules that reflects crystal growth from internal nucleation sites toward their margins. The survival within granules of ACC inclusions for months after they enter soils indicates that they crystallize only within the earthworm and in the presence of fluids containing biochemical catalysts. The earthworm probably promotes crystallization of ACC in order to prevent remobilization of the calcium carbonate by dissolution. Calcite granules vividly illustrate the role of transient precursors in biomineralization, but the underlying question of why earthworms produce granules in volumes sufficient to have a measurable impact on soil carbon cycling remains to be answered. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.