Insights into architecture, growth dynamics, and biomineralization from pulsed Sr-labelled <i>Katelysia rhytiphora</i> shells (Mollusca, Bivalvia)

Abstract

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 µg 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.

Overcoming Challenges Associated with the Analysis of Nacre by Atom Probe Tomography

“…Black mussels Mytilus galloprovincialis (Lamarck 1819) were collected alive from Twofold Bay, New South Wales, Australia, and brought to the Macquarie University Seawater Facility. The bivalves were transferred four times from ambient seawater with~8 lg g -1 strontium to labelling conditions with elevated concentrations of 120 lg g -1 Sr (15 9 mean ocean water) within a period of 35 days by dissolving 2.2 g SrCl 2 •6H 2 O (Otter et al 2018). Strontium has previously been shown to randomly substitute for Ca in the aragonite crystal structure (Foster et al 2009), leading to an increased amount of Sr incorporation during the labelling treatment.…”

Phase-Field Modeling of Biomineralization in Mollusks and Corals: Microstructure vs Formation Mechanism

“…Images showing typical microstructures of mollusk shells of similar type are displayed in Figure 2 . 13 , 26 , 37 , 38 …”

“… Some typical mircrostructures observed in mollusk shells: (a) cross-sectional EBSD orientation map for the shell of Katelysia rhytiphora , 37 the outer side is on the left (note the transitions between layers of different crystallite morphologies); (b) outer randomly oriented granular domain in the shell of Unio pictorum (SEM); 26 (c) columnar prismatic domain of Pinna nobilis (X-ray tomography reconstruction), 13 and (d) plate-like structure of the nacre of Unio pictorum (SEM); 26 (e) spherulitic layer, section perpendicular to growth in the shell of Haliotis rufescens (SEM). 38 [(a) Reproduced from ref ( 37 ) under Creative Commons Attribution 4.0 License. Copyright Authors 2019.…”

Investigating crystal orientation patterns of foraminiferal tests by electron backscatter diffraction analysis

“…Foraminifers are single-celled marine organisms with a protective shell called test, which consists of one or more chambers that are subsequently added during growth (Hausmann et al, 2003;Pawlowski et al, 2003;Holbourn et al, 2013). The characteristics of the tests are the basis for the classification of foraminifera.…”