Structure and crystallography of foliated and chalk shell microstructures of the oyster Magallana: the same materials grown under different conditions

Checa, António; Harper, Elizabeth M.; González-Segura, Alicia

doi:10.1038/s41598-018-25923-6

Cited by 42 publications

(37 citation statements)

References 37 publications

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“…In addition, the deposition of folia produces external features, such as ridges, growth breaks, and other changes in growth direction, thus creating depressions on the interior shell surface that are subsequently filled with chalk. The pattern of chalk formation beneath growth breaks and other external features confirms previous observations that chalk fills in depressions on the interior surfaces of shells 18,20,24,26,27,30,31 , but also provides context for how these depressions form. For oysters, growth breaks represent a significant change in growth direction, and are important in the context of chalk formation because these features are often associated with chalky deposits.…”

Section: Discussionsupporting

confidence: 85%

Structure and distribution of chalky deposits in the Pacific oyster using x-ray computed tomography (CT)

Banker

Sumner

2020

Sci Rep

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Oysters are unusual among bivalves in that they possess chambers, often filled with soft, chalky calcite, that are irregularly scattered throughout the shell. Because the function of these so-called chalky deposits is still unclear, evaluating the growth and distribution of chalk is important for elucidating the ecological function of this unique shell trait. Specimens of the Pacific oyster Magallana gigas, an oyster well known for chalk expression, were grown in Bodega Harbor, Bodega Bay, CA. At the end of an 11 month growing period, specimens were culled and selected animals were submitted for x-ray computed-tomography imaging. Three-dimensional reconstructions of oyster shells were used to assess the overall distribution of chalk, and also to better understand the relationship between chalk and other structures within the shell. Results indicate that chalky deposits underly sculptural features on the shell exterior, such as external ridges and changes in growth direction, and also that there is a relationship between chalk formation and oyster processes of cementation. Overall, chalk is useful for a cementing lifestyle because it enables morphological plasticity needed to conform to irregular substrates, but also acts as a cheap building material to facilitate rapid growth. Many researchers have used preserved remains of shells (molluscan or otherwise) to improve scientific understanding of paleoecosystems and organismal interactions in the fossil record 1-3. Oysters (Bivalvia: Ostreidae) have utility in this setting because they are well preserved in the fossil record, and are widely geographically distributed in paleo and modern ecosystems 4. Moreover, stable isotope and elemental records derived from bivalve shell carbonate reflects the environmental conditions in which the shell grew 5-9. These geochemical datasets have been used to develop proxies, reconstruct paleoclimate, and characterize the environment in which fossil oysters lived (e.g. estuarine versus fully marine) 10-13. Stable isotopes have also been used to assess growth rate, season of death, and the occurrence of phytoplankton blooms in both modern and fossil Ostreids 14-16. Oyster shells are composed primarily of foliated calcite interspersed with lens shaped chambers 17,18. These chambers are irregularly interspersed throughout the shell and are often filled with porous calcite, also referred to as chalk or chalk deposits. It is important to note that chalk is distinct from the vesicular calcite formed by some members of Gryphaeidae (Ostreoidea), which consists of hollow columnar spaces composed of granular calcite, as opposed to the interconnected calcite laths that are characteristic of chalk 19,20. Chambers and chalky deposits are found in both extant and fossil oysters, though the function of these features, particularly chalk and how it forms, has been the subject of much scientific inquiry (e.g. 21-23). Ontogenetically, the formation of chalk commences after the transition to the dissoconch stage when the oyster settles as spat, and co...

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Section: Discussionsupporting

confidence: 85%

Structure and distribution of chalky deposits in the Pacific oyster using x-ray computed tomography (CT)

Banker

Sumner

2020

Sci Rep

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“…However, as shown in a recent study (Sanford et al, 2014), it appears that weaker shell structures will result in compromised defence abilities. Moreover, results from a recent study suggest that oysters with reduced and impaired calcification mechanisms have lower repair capabilities (Coleman et al, 2014). This hierarchical study revealed that the OA conditions may cause a deterioration of oyster shells and thus pose a serious threat to oyster survival and the health of coastal oyster reef structures in the near-future ocean.…”

Section: Ecological Implications and Conclusionmentioning

confidence: 67%

Ocean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis

et al. 2018

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Abstract. The rapidly intensifying process of ocean acidification (OA) due to anthropogenic CO2 is not only depleting carbonate ions necessary for calcification but also causing acidosis and disrupting internal pH homeostasis in several marine organisms. These negative consequences of OA on marine calcifiers, i.e. oyster species, have been very well documented in recent studies; however, the consequences of reduced or impaired calcification on the end-product, shells or skeletons, still remain one of the major research gaps. Shells produced by marine organisms under OA are expected to show signs of dissolution, disorganized microstructure and reduced mechanical properties. To bridge this knowledge gap and to test the above hypothesis, we investigated the effect of OA on juvenile shells of the commercially important oyster species, Magallana angulata, at ecologically and climatically relevant OA levels (using pH 8.1, 7.8, 7.5, 7.2). In lower pH conditions, a drop of shell hardness and stiffness was revealed by nanoindentation tests, while an evident porous internal microstructure was detected by scanning electron microscopy. Crystallographic orientation, on the other hand, showed no significant difference with decreasing pH using electron back-scattered diffraction (EBSD). These results indicate the porous internal microstructure may be the cause of the reduction in shell hardness and stiffness. The overall decrease of shell density observed from micro-computed tomography analysis indicates the porous internal microstructure may run through the shell, thus inevitably limiting the effectiveness of the shell's defensive function. This study shows the potential deterioration of oyster shells induced by OA, especially in their early life stage. This knowledge is critical to estimate the survival and production of edible oysters in the future ocean.

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“…It is composed of an apparently disorganized array of laths. In coincidence, it seemingly displays a high degree of crystallographic disorder (Checa et al, 2018). Although more information is needed on the chalk, it provides an example of how important space restriction is for an effective organization based on crystal competition.…”

Section: Crystal Competitionmentioning

confidence: 99%

Physical and Biological Determinants of the Fabrication of Molluscan Shell Microstructures

Checa

2018

Front. Mar. Sci.

Self Cite

106

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Molluscs are grand masters in the fabrication of shells, because these are composed of the largest variety of microstructures found among invertebrates. Molluscan microstructures are highly ordered aggregates of either calcite or aragonite crystals with varied morphologies and three-dimensional arrangements. Classically, every aspect of the fabrication of microstructural aggregates is attributed to the action of proteins. There was, however, only direct evidence that the mineral phase, and indirect evidence that nucleation and the crystal shape, are determined by the types of soluble proteins. Some authors imply that crystal competition may also play a role. In addition, the fabrication of intergranular organic matrices typical of some microstructures (nacre, columnar prismatic) cannot have a protein-based explanation. Over the last decade I and collaborators have been applying a holistic view, based on analyzing and interpreting the features of both the organic (mantle, extrapallial space, periostracum, organic matrices) and inorganic (crystallite morphology, arrangement, and crystallography) components of the biomineralization system. By interpreting them on biophysical principles, we have accumulated evidence that, in addition to the activity of proteins, other mechanisms contribute in an essential way to the organization of molluscan microstructures. In particular, we have identified processes such as: (1) crystal nucleation on preformed membranes, (2) nucleation and growth of crystals between and within self-organized membranes, (3) active subcellular processes of contact recognition and deposition. In summary, besides the activity of organic macromolecules, physical (crystal competition, self-organization) and/or biological (direct cellular activity) processes may operate in the fabrication of microstructures. The balance between the physical and biological determinants varies among microstructures, with some being based exclusively on either physical or biological processes, and others having a mixed nature. Other calcifying invertebrates (e.g., corals, cirripeds, serpulids) secrete microstructures that are very similar to inorganic crystal aggregates, and only some brachiopods and, to a lesser extent, bryozoans may have secretory abilities comparable to those of molluscs. Here I provide a new perspective, which may allow microstructures to be understood in terms of evolutionary constraints, to compare the secretional abilities among taxa, and even to evaluate the probability of mimicking microstructures for the production of functional synthetic materials.

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Structure and crystallography of foliated and chalk shell microstructures of the oyster Magallana: the same materials grown under different conditions

Cited by 42 publications

References 37 publications

Structure and distribution of chalky deposits in the Pacific oyster using x-ray computed tomography (CT)

Structure and distribution of chalky deposits in the Pacific oyster using x-ray computed tomography (CT)

Ocean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis

Physical and Biological Determinants of the Fabrication of Molluscan Shell Microstructures

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