Acanthopleura Hirtosa Research Articles

Quantum Magnetic Imaging of Iron Biomineralization in Teeth of the Chiton Acanthopleura hirtosa

AbstractIron is critical for life. Nature capitalizes on the physical attributes of iron biominerals for functional, structural, and sensory applications. Iron biomineralization is well exemplified by the magnetite‐bearing radula of chitons, the hardest known biomineral of any animal. Although magnetism is an integral property of iron biominerals, limited information exists on the magnetic state, structure, and orientation of these nanoscale materials during mineralization. The advent of quantum‐based magnetic microscopy provides a new avenue to probe these biological systems directly, providing detailed magnetic information of the iron oxide structures. Here two complementary quantum magnetic microscopy methods are applied, based on nitrogen‐vacancy centers in diamond, to spatially map the mineral phases ferrihydrite and magnetite in the developing teeth of the chiton Acanthopleura hirtosa. The images reveal previously undiscovered long‐range magnetic order, established at the onset of magnetite mineralization. This is in contrast to electron microscopy studies that show no strong common crystallographic orientation. The implications of these results are important, not just for the insights gained in biomineralization of the target organism, but also for the study of a broad range of iron minerals in the physical and biological sciences.

Erratum to “Characterization of biominerals in the radula teeth of the chiton, Acanthopleura hirtosa” [J. Struct. Biol. 167 (2009) 55–61

Erratum to “Characterization of biominerals in the radula teeth of the chiton, Acanthopleura hirtosa” [J. Struct. Biol. 167 (2009) 55–61

Characterization of biominerals in the radula teeth of the chiton, Acanthopleura hirtosa

Understanding biomineralization processes provides a route to the formation of novel biomimetic materials with potential applications in fields from medicine to materials engineering. The teeth of chitons (marine molluscs) represent an excellent example of a composite biomineralized structure, comprising variable layers of iron oxide, iron oxyhydroxide and apatite. Previous studies of fully mineralized teeth using X-ray diffraction, Raman spectroscopy and scanning electron microscopy (SEM) have hinted at the underlying microstructure, but have lacked the resolution to provide vital information on fine scale structure, particularly at interfaces. While transmission electron microscopy (TEM) is capable of providing this information, difficulties in producing suitable samples from the hard, complex biocomposite have hindered progress. To overcome this problem we have used focused ion beam (FIB) processing to prepare precisely oriented sections across interfaces in fully mineralized teeth. In particular, the composite structure is found to be more complex than previously reported, with additional phases (goethite and amorphous apatite) and interface detail observed. This combination of FIB processing and TEM analysis has enabled us to investigate the structural and compositional properties of this complex biocomposite at higher resolution than previously reported and has the potential to significantly enhance future studies of biomineralization in these animals.

Ultrastructure of the Epithelial Cells Associated with Tooth Biomineralization in the ChitonAcanthopleura hirtosa

The cusp epithelium is a specialized branch of the superior epithelium that surrounds the developing teeth of chitons and is responsible for delivering the elements required for the formation of biominerals within the major lateral teeth. These biominerals are deposited within specific regions of the tooth in sequence, making it possible to conduct a row by row examination of cell development in the cusp epithelium as the teeth progress from the unmineralized to the mineralized state. Cusp epithelium from the chiton Acanthopleura hirtosa was prepared using conventional chemical and microwave assisted tissue processing, for observation by light microscopy, conventional transmission electron microscopy (TEM) and energy filtered TEM. The onset of iron mineralization within the teeth, initiated at row 13, is associated with a number of dramatic changes in the ultrastructure of the apical cusp cell epithelium. Specifically, the presence of ferritin containing siderosomes, the position and number of mitochondria, and the structure of the cell microvilli are each linked to aspects of the mineralization process. These changes in tissue development are discussed in context with their influence over the physiological conditions within both the cells and extracellular compartment of the tooth at the onset of iron mineralization.

The chiton stylus canal: An element delivery pathway for tooth cusp biomineralization

A detailed investigation of the stylus canal situated within the iron mineralized major lateral teeth of the chiton Acanthopleura hirtosa was undertaken in conjunction with a row-by-row examination of cusp mineralization. The canal is shown to contain columnar epithelial tissue similar to that surrounding the mineralized cusps, including the presence of iron rich particles characteristic of the iron storage protein ferritin. Within the tooth core, a previously undescribed internal pathway or plume is evident above the stylus canal, between the junction zone and mineralizing posterior face of the cusp. Plume formation coincides with the appearance of iron in the superior epithelium and the onset of mineralization at tooth row 13. The plume persists during the delivery of phosphorous and calcium into the tooth core, and is the final region of the cusp to become mineralized. The presence of the stylus canal was confirmed in a further 18 chiton species, revealing that the canal is common to polyplacophoran molluscs. These new data strongly support the growing body of evidence highlighting the importance of the junction zone for tooth mineralization in chiton teeth, and indicate that the chemical and structural environment within the tooth cusp is under far greater biological control than previously considered.

Methods of sample preparation of radula epithelial tissue in chitons (Mollusca: Polyplacophora)*

A glutaraldehyde fixative developed for preserving the radula superior epithelium of the adult chiton Acanthopleura hirtosa (Blainville, 1825), was used in conjunction with conventional and microwave-assisted sample processing to produce high quality tissue preservation for light and electron microscopy. In addition, high-pressure freezing (HPF) and cryo-substitution were used to fix the radula tissue of juvenile specimens. Microwave-assisted fixation was preferred to conventional bench-top techniques due to the superior preservation of fine cell structure together with reduced processing times and chemical exposure. Although restricted to very small (<200 μm) samples, the quality of juvenile radulae processed by HPF was excellent. The improvements in tissue preservation using microwave and cryo-preservation techniques are therefore critical for obtaining accurate ultrastructural information on the radula in marine molluscs. In particular, these findings highlight additional processing options available for the study of cellular structures in biomineralizing tissues.

Radula Tooth turnover in the chiton Acanthopleura hirtosa (Blainville, 1825) (Mollusca: Polyplacophora)

The rate of radula production in the chiton Acanthopleura hirtosa (Blainville, 1825) was determined by following structural irregularities induced in the radula using a cold-shock treatment of 4°C for 48 h. In animals treated in this manner and subsequently maintained in an artificial intertidal habitat to ensure, as far as possible, a natural feeding regimen, the rate of radular production was calculated as 0.36 rows per day. This indicates that A. hirtosa renews its total radular length (mean 78 rows, SD = 6.5, n = 23) approximately once every 6.5 months, a relatively slow rate when compared with that of other molluscs.

In situ Raman spectroscopic studies of the teeth of the chiton Acanthopleura hirtosa

In situ Raman spectroscopy, in combination with energy dispersive spectroscopy, has been used for the first time to determine the identities and locations, at the micron level, of mineral phases present in single chiton teeth that have been extensively mineralized. At the later stages of development the major lateral teeth of the chiton Acanthopleura hirtosa show characteristic spectroscopic evidence for the presence of lepidocrocite (γ- FeOOH), magnetite (Fe3O4), and an apatitic calcium phosphate, Goethite (α- FeOOH) and ferrihydrite (5Fe2O3·9H2O), which have been detected previously in teeth at the early stages of mineralization, were not detected in this mature tooth. The spatial distribution of these phases was determined, providing evidence for the presence of a discrete layer of lepidocrocite between the magnetite and apatite regions, illustrating the complexity of the biomineralization process. The technique of laser Raman microscopy is shown to be ideal for the examination of small biomineralized structures in situ, such as chiton teeth.

Calcium biomineralization in the radular teeth of the chiton, Acanthopleura hirtosa.

A method has been devised for isolating the calcium biomineral from the iron biominerals and organic components present in the major lateral teeth of the chiton Acanthopleura hirtosa. Fourier-transform infrared spectroscopy of the calcium biomineral indicated that it was an apatite material containing carbonate and fluoride ions. Carbonate was not found to be present as a separate phase. The apatite was further separated into low and high density fractions, both of which showed crystallinity intermediate between that of bovine tibia cortical bone and human tooth enamel, as indicated by powder X-ray diffraction analysis. The calcified region of the major lateral teeth was also studied in situ using transmission electron microscopy and electron diffraction analysis, revealing a close spatial relationship between the mineral apatite phase and underlying organic matrix. It is suggested that the architectural arrangement of apatite biomineral and fibrous organic constituents imparts specialized mechanical properties to the tooth making it ideally suited for the task of obtaining food from hard surfaces.

Characterization and structural organization of the organic matrix of the radula teeth of the chiton Acanthopleura hirtosa

The organic matrix of the radula teeth of the chiton Acanthopleura hirtosa has been examined by a variety of techniques to identify and partially characterize the major structural component and to elucidate the complex architectural arrangement of matrix fibres. The teeth are initially composed solely of organic material, a major component of which has been identified as the partially deacetylated α-polymorph of the polysaccharide, chitin. The matrix consists of organic fibres, with significant changes in the organization and distribution of fibres occurring in the early stages of tooth development, presumably in preparation for the onset of mineralization. Organic fibres in the posterior region of the tooth cusp become progressively more sparse and poorly ordered. In contrast, the anterior section of the cusp becomes more structured, consisting of a series of highly ordered rope-like fibres. At high magnification these fibres can be seen to consist of hollow tubules linked by fine strands or bridges. Demineralized mature teeth show the same variation in the fibre density and arrangement. It is suggested both that mineralization occurs on a preformed organic framework of which the fibrous bridges are an integral component and that the organization of the matrix fibres together with the architecturally discrete distribution of minerals contributes significantly to the overall mechanical properties of the tooth.

Biomineralization of iron: Moessbauer spectroscopy and electron microscopy of ferritin cores from the chiton Acanthopleura hirtosa and the limpet Patella laticostata

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBiomineralization of iron: Moessbauer spectroscopy and electron microscopy of ferritin cores from the chiton Acanthopleura hirtosa and the limpet Patella laticostataT. G. St. Pierre, K. S. Kim, J. Webb, S. Mann, and D. P. E. DicksonCite this: Inorg. Chem. 1990, 29, 10, 1870–1874Publication Date (Print):May 1, 1990Publication History Published online1 May 2002Published inissue 1 May 1990https://doi.org/10.1021/ic00335a022RIGHTS & PERMISSIONSArticle Views202Altmetric-Citations33LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Isolation and characterization of ferritin from the hepatopancreas of the musselMytilus edulis

The main iron-binding protein in the hepatopancreas of the mussel Mytilus edulis, which had been previously iron-loaded by exposure to carbonyl iron (spheres of elemental iron less than 5 μm diameter), has been isolated to electrophoretic purity and identified as ferritin. This ferritin has Mr, of 480000, pI of 4.7-5.0 and is composed of two subunits, Mr 18500 and Mr 24600. Under the electron microscope, it appears as electron-dense iron cores of average diameter 5 nm surrounded by a polypeptide shell to a final average overall diameter of 11 nm. The purified protein contains, on average, 200 iron atoms/molecule protein. On immunodiffusion, M. edulis hepatopancreas ferritin gives a partial cross-reaction with antiserum to horse spleen ferritin and lamprey (Geotria australis) liver ferritin but does not react with antiserum to chiton (Acanthopleura hirtosa) haemolymph ferritin.