Micro‐ to nanostructure and geochemistry of extant crinoidal echinoderm skeletons

Abstract

This paper reports the results of micro- to nanostructural and geochemical analyses of calcitic skeletons from extant deep-sea stalked crinoids. Fine-scale (SEM, FESEM, AFM) observations show that the crinoid skeleton is composed of carbonate nanograins, about 20-100 nm in diameter, which are partly separated by what appears to be a few nm thick organic layers. Sub-micrometre-scale geochemical mapping of crinoid ossicles using a NanoSIMS ion microprobe, combined with synchrotron high-spatial-resolution X-ray micro-fluorescence (μ-XRF) maps and X-ray absorption near-edge structure spectroscopy (XANES) show that high Mg concentration in the central region of the stereom bars correlates with the distribution of S-sulphate, which is often associated with sulphated polysaccharides in biocarbonates. These data are consistent with biomineralization models suggesting a close association between organic components (including sulphated polysaccharides) and Mg ions. Additionally, geochemical analyses (NanoSIMS, energy dispersive spectroscopy) reveal that significant variations in Mg occur at many levels: within a single stereom trabecula, within a single ossicle and within a skeleton of a single animal. Together, these data suggest that physiological factors play an important role in controlling Mg content in crinoid skeletons and that great care should be taken when using their skeletons to reconstruct, for example, palaeotemperatures and Mg/Ca palaeo-variations of the ocean.

Ultrascale and microscale growth dynamics of the cidaroid spine of Phyllacanthus imperialis revealed by 26Mg labeling and NanoSIMS isotopic imaging

“…Indeed, the laminated structure of the cidaroid spine composed of up to about 1-lm thick layers revealed by the slight etching (Fig. 3) is commonly observed among representatives of all echinoderm classes (e.g., Gorzelak et al, 2011Gorzelak et al, , 2013. It has been hypothesized that this lamination pattern must represent successive growth episodes (Dubois, 1991;Seto et al, 2004).…”

“…6 in Gorzelak et al, 2011; fig. 1 in Gorzelak et al, 2013). The thickness of individual layers ranges from 0.7 to 1.2 lm (Fig.…”

“…Ion transport is likely mediated by pumps, channels, and cotransporters as evidenced in sea urchin larvae (Dubois and Chen, 1989 for a review; Stumpp et al, 2012). Various organic components and amorphous calcium carbonate phases could also be involved in the ion transport in echinoderms (Gorzelak et al, 2013 for a review). Nevertheless, the actual path of ion transport into the calcification site in adult echinoderms is completely unexplored.…”

Computer-integrated polarisation (CIP) in the analysis of fossils: a case of study in a Palaeozoic coral (Sinopora, Syringoporicae, Carboniferous)

“…In topography image, some nanogranules present a rim around them, with other topography indicating that the compositional variation is part of other phase or a mixing of phases. Several authors (Dauphin 2002;Cuif et al 2008;Gorzelak et al 2013) have studied these envelopes in recent and fossil organisms and proposed that they could be organic coatings from the original organic matrix.…”

Trace element accumulation in the shell of the Arctic cirriped Balanus balanus

“…On the other hand, higher sulphur concentrations may indicate a greater content of organic material in the calcareous lattice (Lorens & Bender, 1980;Vander Putten et al, 2000). In calcitic shells of brachiopods, Cusack et al (2008) found sulphur in a form of sulphate and sulphur-containing amino acids (proteins), whereas Gorzelak et al (2013) recorded that in crinoids calcite sulphur was associated with sulphated polysaccharides. In addition, Gorzelak et al (2013) observed that high Mg concentrations in the skeleton were correlated with the distribution of sulphates, and this pattern agrees with our results (Fig.…”