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Guinea fowl eggshell is characterized by:
A bilayered calcified structure
A main shift of crystal size at approximately 1/3 of the total thickness (11h post ovulation), followed by a secondary nucleation event
A non homogeneous distribution of occluded organic matter
The shift in eggshell fabric between these layers is accompanied by changes in the distribution and amount of intra-crystalline organic matter.
k k
Fig 3 : Optical microscopy view of the cross-section of a fully formed eggshell, EBSD crystal orientation and local misorientation maps of the eggshell cross-section.
main shift between the two
distinct eggshell microstructure lay the start of the secondary
nucleation event
4 hours post ovulation : Onset of mineralisation with deposition of « seeding sites »
5 Hours P.O.: One hour later, the eggshell membrane is almost fully covered by semi- spherical aggregates of calcite crystals
11 hours P.O.: Cross-section view of an eggshell collected at 11 hrs p.o., showing a sharp
microstructure change from large columnar calcite crystal units to calcite microcrystals
24 hours P.O.: A fully formed eggshell with the lower part formed by large columnar units (lower part) and the top part form by smaller calcite crystal units arranged with a brick-wall microstructure
5h P.O.
G u i n e a f o w l e g g s h e l l q u a n ti t a ti v e p r o t e o m i c s y i e l d n e w fi n d i n g s r e l a t e d t o i t s u n i q u e s t r u c t u r a l c h a r a c t e r i s ti c s a n d s u p e r i o r m e c h a n i c a l p r o p e r ti e s
N. Le Roy
1, A. Brionne
1, V. Labas2, L. Combes-Soia
2, A. Rodriguez-Navarro
3, M.T. Hincke
4, J. Gautron
11
BOA, INRA, Université de Tours, 37380 Nouzilly, France
2
UMR PRC, INRA 85, CNRS 7247, Université de Tours, IFCE, 37380 Nouzilly, France
3
Departmento de Mineralogia y Petrologia, Universidad de Granada, 18071 Granada, Spain
4
Department of Innovation in Medical Education, University of Ottawa, Canada
The Guinea fowl eggshell is a bioceramic material with the remarkable mechanical property of being twice as strong as the chicken eggshell (Fig 1). Both eggshells are composed of 95% mineral in the calcitic form and 3.5%
organic matrix, which control its structural organization. Chicken eggshell is made of columnar calcite crystal units arranged vertically. In Guinea fowl, the same structure is observed in its inner half, followed by a dramatic change in crystal size and orientation in the outer region (Fig 2). Shell characteristics (more complex structure and greater shell thickness), confer a superior resistance to breakage compared to eggshells of other bird species. To understand the underlying mechanisms controlling the structural organization of this highly resistant material, we used physical and quantitative proteomics methods to analyze the ultrastructure and protein composition of the Guinea fowl eggshell organic matrix at key stages of the mineralization process.
The Guinea fowl eggshell is a bioceramic material with the remarkable mechanical property of being twice as strong as the chicken eggshell (Fig 1). Both eggshells are composed of 95% mineral in the calcitic form and 3.5%
organic matrix, which control its structural organization. Chicken eggshell is made of columnar calcite crystal units arranged vertically. In Guinea fowl, the same structure is observed in its inner half, followed by a dramatic change in crystal size and orientation in the outer region (Fig 2). Shell characteristics (more complex structure and greater shell thickness), confer a superior resistance to breakage compared to eggshells of other bird species. To understand the underlying mechanisms controlling the structural organization of this highly resistant material, we used physical and quantitative proteomics methods to analyze the ultrastructure and protein composition of the Guinea fowl eggshell organic matrix at key stages of the mineralization process.
INTRODUCTION
Gallus gallus Numida meleagris
Figure 1. Eggshell breaking strength vs egg size Figure 2. Laying hens and Guinea fowl eggshell structures
EXPERIMENTAL PROCEDURES
First mineralisation events
Large crystal units just before the shif
Onset of crystal shif
Development of new crystalline
shape
Change in the size and orientation of crystals (shif)
Massive deposition of new crystalline layer
Eggshells were collected at the main stages of shell calcification before and after dramatic change of crystal size (4, 10, 11, 12 and 18h post ovulation) and at completion (26h post ovulation)
10 h p.o, 4 h p.o,
11 h p.o, 12 h p.o,
18 h p.o,
❶ In situ measurements ❷ Quantitative Proteomic analysis of eggshell matrix proteins
RESULTS ❶ In situ measurements
(Rodriguez-Navarro et al;, 2019)Fig 4 : SEM observation of the forming eggshells at the key stages of shell mineralization
Comparison with the eggshell proteome of other archosaurian species
2a
Protein identification and
quantification at various stages during the Guinea fowl eggshell mineralization
2b
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