In vivo characterization of bivalve larval shells: a confocal Raman microscopy study

Abstract

confocal Raman microscopy (CRM), polarized light microscopy and Fourier transform infrared spectroscopy (FTIR) were used to determine if a significant amount of amorphous calcium carbonate (ACC) exists within larval shells of Baltic mytilid mussels (-like) and whether the amount of ACC varies during larval development. No evidence for ACC was found from the onset of shell deposition at 21 h post-fertilization (hpf) until 48 hpf. Larval shells were crystalline from 21 hpf onwards and exhibited CRM and FTIR peaks characteristic of aragonite. Prior to shell deposition at 21 hpf, no evidence for carbonates was observed through CRM. We further analysed the composition of larval shells in three other bivalve species, , and and observed no evidence for ACC, which is in contrast to previous work on the same species. Our findings indicate that larval bivalve shells are composed of crystalline aragonite and we demonstrate that conflicting results are related to sub-optimal measurements and misinterpretation of CRM spectra. Our results demonstrate that the common perception that ACC generally occurs as a stable and abundant precursor during larval bivalve calcification needs to be critically reviewed.

The PteropodCreseis aciculaForms Its Shell through a Disordered Nascent Aragonite Phase

“…These are all characteristics of ACC rather than a more ordered mineral phase. Ramesh et al studied the larvae of the bivalve Mytilus edulis and reported results very similar to those reported here for C. acicula , namely, the presence of a nascent partly ordered phase and no evidence for ACC. The above studies do show that in certain cases ACC, as opposed to a nascent partly ordered first mineral deposit, can be detected spectroscopically in mollusks.…”

Coupling Mineralogy and Oxygen Isotopes to Seasonal Environmental Shifts Recorded in Modern Freshwater Pearl Nacre From Kentucky Lake

“…Average Raman shift positions in wavenumber (cm −1 ) for each peak are presented in Table 1 and indicate that they are comparable to results from previous mollusk Raman studies (Beierlein et al, 2015;Nehrke & Nouet, 2011;Urmos et al, 1991). In this study, we see no evidence of other carbonate phases, such as calcite or vaterite which have been observed and mapped by Raman spectroscopy in an Antarctic mollusk study (Nehrke et al, 2012), or amorphous calcium carbonate (ACC) observed via Raman spectroscopy in larval bivalves (Ramesh et al, 2018) or via coupled photoemission electron spectromicroscopy (PEEM) and X-ray absorption near-edge structure (XANES) in fresh red abalone (DeVol et al, 2015). Since we used a red 785 nm laser for our measurements, and the pearls in our study are white and unpigmented, we did not observe clear Raman signatures for pigments (or vaterite associated with some of these pigments) described in previous studies on pigmented saltwater and freshwater pearls (Karampelas et al, 2019;Soldati et al, 2008).…”

Structure and Composition of the Eggshell of a Passerine Bird,Setophaga ruticilla(Linnaeus, 1758)

“…"Lattice" or "external" modes in the region 100-400 cm −1 are absent in ACC and differ in crystalline CaCO 3 (Fig. 9a; Gierlinger et al, 2013;Ramesh et al, 2018). Both samples show the peaks characteristic for these polymorphs, but aragonite also comprises some peaks probably due to the presence of organic components.…”