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The Biological Crystals in Chamid Bivalve Shells: Diversity in Morphology and Crystal Arrangement Pattern

Authors :
Sebastian Hoerl
Erika Griesshaber
Antonio G. Checa
Wolfgang W. Schmahl
Source :
Crystals, Vol 14, Iss 7, p 649 (2024)
Publication Year :
2024
Publisher :
MDPI AG, 2024.

Abstract

Chamid bivalves are marine organisms that live in high-energy environments and are cemented to hard substrates. To avoid shell damage, the organisms form thick, densely ornamented shells. Shell material consists of aragonite, and the ornamentation may be either aragonitic or calcitic. The latter can be developed as scaly spines, rows of blades, or comarginal, radial arched lamellae. We investigated biological crystal morphology and mode of assembly of Chama arcana and Chama gryphoides shells. Structural characteristics were obtained from electron backscatter diffraction (EBSD) measurements, complemented with laser confocal and BSE imaging. We found a wide range of crystal morphologies and sizes, ranging from irregularly shaped calcite and/or aragonite prisms to tiny and thin aragonite laths. We observed four different modes of crystal assembly patterns: 1. strongly interlocked dendritic calcite units forming the ornamentation blades; 2. aragonite laths arranged to lamellae forming the outer shell layer, the layer adjacent to the calcite; 3. aragonite laths arranged into blocks comprising inner shell layers or aragonitic ornamentations; and 4. shell portions consisting of aragonite prisms, structured in size and crystal orientation, at muscle attachment sites. These four different types of crystal arrangements were observed for the shells of the investigated chamid species; however, they had slightly different strengths of structuring and slight variations in crystal organisation. Additionally, we observed unique microstructural features in Chama shells: We report ornamentation crystals resembling idiomorphic calcite and novel, twinned entities found at the changeover between the aragonitic layers. We highlight and discuss these differences and anomalies in this contribution.

Details

Language :
English
ISSN :
20734352
Volume :
14
Issue :
7
Database :
Directory of Open Access Journals
Journal :
Crystals
Publication Type :
Academic Journal
Accession number :
edsdoj.51d7b01ef2044e2ab9c047b64079cdb7
Document Type :
article
Full Text :
https://doi.org/10.3390/cryst14070649