Insights into architecture, growth dynamics, and biomineralization from pulsed Sr-labelled Katelysia rhytiphora shells (Mollusca, Bivalvia)
2019
Abstract. The intertidal bivalve Katelysia rhytiphora, endemic to south Australia and Tasmania,
is used here for pulsed Sr-labelling experiments in aquaculture experiments
to visualize shell growth at the micro- to nanoscale. The ventral margin
area of the outer shell layer composed of (i) an outermost outer shell layer
(oOSL) with compound composite prismatic architecture with three
hierarchical orders of prisms and (ii) an innermost outer shell layer (iOSL)
with crossed-acicular architecture consisting of intersecting lamellae
bundles. All structural orders in both layers are enveloped by an organic
sheath and the smallest mineralized units are nano-granules. Electron
backscatter diffraction reveals a strong preferred orientation of the
aragonite c axes perpendicular to the growth layers, while the a and b axes
are scattered within a plane normal to the local growth direction and
>46 % twin grain boundaries are detected. The Young's modulus
shows a girdle-like maximum of elastically stiffer orientations for the
shell following the inner shell surface. For 6 d, the bivalves were subjected twice to seawater with an increased
Sr concentration of 18× mean ocean water by dissolving 144 µ g g −1 Sr (159.88 Sr∕Ca mmol ∕ mol) in seawater. The pulse
labelling intervals in the shell are 17× (oOSL) and 12× (iOSL) enriched in
Sr relative to the Sr-spiked seawater. All architectural units in the shell
are transected by the Sr label, demonstrating shell growth to progress
homogeneously instead of forming one individual architectural unit after the
other. Distribution coefficients, DSr ∕ Ca , for labelled and unlabelled shells are similar to shell
proportions formed in the wild (0.12 to 0.15). All DSr ∕ Ca values are lower than
values for equilibrium partitioning of Sr in synthetic aragonite.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
97
References
4
Citations
NaN
KQI