Integrated Information on the Structure and Composition of the Ostrich Eggshell (Struthio camelus)

Round 1

Reviewer 1 Report

Dear Authors,

 Thank you for the opportunity to review the manuscript (minerals-2260948) (Integrated information on the structure and composition of the ostrich eggshell (Struthio camelus)) by Perez-Huerta and co-authors, submitted for possible publication in Minerals. You submitted an interesting manuscript about mineral, crystallographic and chemical characterization of Struthio eggshells.

 The result of this good work is remarkable. The manuscript is well written, organized, presented on a series of illustrative figures, and to the point.

Most of my comments refer to the composition of some terms, methods used and some figure. I suggested some minor corrections in the uploaded text.

 My comments are:

 1) It is visible a broadening in the Raman peaks of the outer layer (v1, v2, lattice modes), which could be related with some disordering in calcite lattice by P and Mg incorporation. I would deep this possibility. Moreover, I would add in Supplementary Figures a spectrum of the center of a spherolitic structure of mamillary layer, which seems disordered in the diffraction intensity maps of EBSD.

2) Figure 2f. It would be desirable the inverse image, rendering the channels, instead of the eggshell. This will favor the visualization of porosity interconnection. Like Pérez-Huerta et al. (2009). Journal of Structural Biology, 167.

3) The number of samples analyses is missing in the Material section, and the preservation state of them during sampling (e.g., hatched, broken, unaltered or fresh...).

4) After reading, I consider that the starting preservation of the eggshell may, somehow, constrain the preservation state of organic layers, which can be partially removed, as you suggest in the text, but also change during early diagenesis stages in solid, for example in the outer parts of the eggshell, crystallizing amorphous phases by higher temperatures or weathering, microorganisms’ activity... Could you discuss this in the Discussion section?

 With best regards,

 Reviewer

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript "Integrated information on the structure and composition of the ostrich eggshell (Struthio camelus)" is a deep study about the mineral structure and composition of ostrich eggshell. I consider that this manuscript deserves to be publishe in Minerals journal.

I only have some minor observations:

1. page 3: "...tetrafluoromethane (1/1 v/v) for 6h 30 at 35 W, so..." Do you mean 6 h 30 minutes?

2. page 4, section 2.7: change "Data was" for "Data were"

3. page 6, figure 2i: you wrote "whereas between the pores, the prisms are clearer in BSE SEM images". I was not able to identify the prisms. Please, indicate them in the figure.

4. page 9, figure 5i: you wrote "Locally, a fold suggest that this structure is soft, organic (Figure 5i, arrow)" Can this fold be a cristallyne defect and not necessarily an evidence of soft material?

5.page 10, figure 6a:  you wrote "are absent in the non-biogenic calcite, as well as those at 2982 and 2512 cm-1." However, in the figure it is possible to observe those peaks in the non-biogenic calcite spectrum. Please, explain better what you mean.

6. page 10: you wrote v4 but must be u4. Correct the same mistake for all pages.

7. page 11, figure 7: please, explain clearly how Figure 7b was obtained and its interpretation. Also, in Figure 7a there is an inset to the right. Explain what this inset represents.

8. page 12,13, Figures 8 and 9: please explain what A1 and A2 represent in the stereographic projection

9.page 15, figure 11: is it the horizontal axis in keV units? If it is, then you wrote the following wrong: "Spectra of the extracted organic matrices are similar, but not identical: the soluble organic matrix has a smooth bump at 21687eV, meanwhile the insoluble matrix has two small peaks within the bump (21675 and 21694 eV) (Figure 11)." Please, check the units.

10. Table 1 legend: please, explain in the legend all the coefficients represented and how they were obtained

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I enjoyed reading this manuscript by Perez-Huerta et al. updating in modern terms and with new methods structural features of the ostrich eggshell.  The study is thorough, careful and informative as performed by experts in the field.  The work provides new detail about the ostrich eggshell, as well as clearing up previous misconceptions from past work long ago.  State-of-the-art methods are used to characterize different regions, additionally including atomic force microscopy, which is not used by many in the field, but which provides important nano-scale resolution information.  The ostrich eggshell has some unique properties, and a discussion of these has been articulated in the manuscript.

I have the following minor points.

 

1)  Consider and check carefully everywhere about using Spongy Layer versus Palisade Layer, as the latter is more commonly used.  Also, use of PL for outer prismatic layer is confusing with Palisades Layer.

 

2)  Page 2. "intraskeletal" organic matrix of eggshells ... I don't think this is a good word to use.  No one I know refers to eggshell as being skeletal.

 

3) Page 3.  Why carb chitin used as an organic standard - needs a better explanation.

 

4)  Page 4 and elsewhere. NaCIO appears to be written with an upper  "I" rather than a lower case "l".  Also, write sodium hypochlorite in the first instance. 

5)  Page 5.  It would seem that sodium hypochlorite "soaking" for 1 hr (not "dipping") would remove only surface contaminants, not interior organics.  Clarify with better language. 

6)  A better description of the nanostructure is required as viewed by AFM, with more discussion related to the context and content of Science Adv paper by Athanasiadou 

7)  Page 15.  The McKee lab has shown in chicken eggshell that the "organic coating on the walls of the pores" contains osteopontin.  Reference to this might be cited.

Author Response

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Author Response File: Author Response.pdf