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Biomineralization on crinoid echinoderms. Characterization of crinoid skeletal elements using TEM and STEM
Scanning Electron Microscopy
|January 1, 1981
Summary
This study reveals that the magnesium calcite in stalked crinoid skeletons is remarkably homogeneous, suggesting significant biological control over mineralization. These findings on Neocrinus blakei columnals may apply to crinoids generally.
Area of Science:
- Marine Biology
- Paleontology
- Biomineralization
Background:
- Stalked crinoids, like Neocrinus blakei, possess unique skeletal structures.
- Understanding the composition and structure of these skeletons provides insights into marine invertebrate biology.
Purpose of the Study:
- To analyze the composition and microstructure of magnesium calcite in Neocrinus blakei columnals.
- To investigate the homogeneity and crystal structure of crinoid stereom.
- To explore the implications for biomineralization processes in echinoderms.
Main Methods:
- Powder X-ray diffraction and electron microprobe analysis for chemical composition.
- Scanning transmission electron microscopy (STEM) for microanalytical data.
- Transmission electron microscopy (TEM) and selected area electron diffraction (SAD) for structural analysis.
Main Results:
- Crinoid stereom is composed of Ca88Mg12CO3 (magnesium calcite).
- Magnesium incorporation is random and homogeneous down to 20 nm.
- Skeletal plates are single crystals with a mosaic structure of ~1.0 micrometer crystallites.
Conclusions:
- The homogeneous composition suggests a strong "vital effect" (biologic control) in mineralization.
- The mosaic structure may explain the lack of cleavage in echinoderm skeletal fractures.
- Findings are potentially applicable to other deep-water stalked crinoids in stable environments.