Emu Eggshell Research Articles

Anisotropic fracture resistance of avian eggshell

In order to understand the fracture toughness anisotropy of avian eggshells, we have investigated eggshells of the emu (Dromaius novaehollandiae) whereby the large size (~13 cm × 9.5 cm) enabled the fabrication of beam samples in various orientations. The emu eggshell was found to have a hierarchical microstructure similar to chicken eggshell, with the only significant difference being the absence of a continuous cuticle layer. Emu eggshell was found to have significantly lower strength when samples were tested in the outwards direction (i.e., a crack initiates on the inside of the shell and propagates towards the outer surface) as compared to the inwards testing direction. Furthermore, samples that were oriented parallel to the egg axis (i.e., the longitudinal direction) and tested inwards showed higher strength, ~24 MPa, compared to the samples that were made from the latitudinal orientation, ~20 MPa. Independent of orientation, the outwards testing direction resulted in strength values of ~15 MPa. The fracture toughness of the emu eggshell for cracking in the circumferential direction was ~0.3 MPa√m, independent of sample orientation, and this value was comparable to the fracture toughness of chicken eggshell tested in the same orientation. In the radial outwards direction, however, the fracture toughness was ~80% lower (~0.06 MPa√m) than in the circumferential direction. The low fracture toughness for this orientation was associated with the separation of the highly oriented calcite crystals in the mammillary cone layer of the eggshell structure which is easier compared to calcite crystal fracture. The large anisotropy in fracture toughness is thought to allow for easy escape of the chick while simultaneously protecting the embryo during development.

Calcium Carbonate Crystal Shapes Mediated by Intramineral Proteins from Eggshells of Ratite Birds and Crocodiles. Implications to the Eggshell’s Formation of a Dinosaur of 70 Million Years Old

In this contribution we want to show how the intramineral proteins affect the crystal morphology of calcite crystals grown in vitro. Intramineral proteins from emu eggshells and two crocodile species were isolated, purified by ultrafast liquid chromatography, and characterized by biochemical and biophysical methods. We saw that the crystal habit of calcite was modified when intramineral proteins were present at certain concentration. Therefore, all crystal species were individually characterized by scanning electron microscopy (SEM) and by electron diffraction with an electron-reduced dosage in transmission electron microscopy. Additionally, transversal SEM micrographs of eggshells of four types of species, namely, emu, crocodile, hen, and dinosaur (70 million years old), were compared to track the changes produced by the interacting intramineral proteins. Finally, the organic sulfur content analysis of these eggshells was performed by using X-ray absorption techniques like X-ray fluorescence and X-ray absorption near-edge structure. From the analyses of the dinosaur eggshells, these X-ray absorption data showed a very characteristic organic sulfur bonding similar to that semiessential proteogenic amino acid l-cysteine, which implies that there is a possibility of having a very old intramineral protein similar to those found in emu and crocodiles.

Explaining the lack of emu eggshell material culture in Australia: Experimental working and archaeological implications

Ostrich eggshell (OES) disc beads are among the earliest types of personal adornment produced by Modern Human populations in African and Asia, and represent the first example of a raw material transformed into an entirely new shape — as opposed to simply perforating a whole marine shell — for decorative purposes. These same beads have continued to be made into present day as an important item in modern gift-exchange systems in sub-Saharan Africa, while OES has a similarly long history for being used as water (etc.) containers. Given the importance of OES to so many communities through time and space, questions regarding why a similar use of emu eggshell (EES) is completely absent from the Australian context is frequently voiced in archaeological forums. This paper will address that question through experimental replication of both OES and EES disc beads for direct comparison of their manufacture and use characteristics. It was found that while it is possible to successfully create disc beads in EES, there are several factors which make this raw material unsuitable for use in either social or utilitarian technologies.

Isolation of Biliverdin IXα, as its Dimethyl Ester, from Emu Eggshells

A laboratory experiment is described that extracts the tetrapyrrolic teal-colored biliverdin IXα, as its dimethyl ester, from commercially available emu eggshells. The extraction of ∼10 mg samples of biliverdin is simple and requires two 3 h lab periods: A two-step acid digestion and liquid–liquid extraction, followed by short silica gel flash column chromatography. The deeply colored extract can be characterized by TLC, UV–vis, IR, 1H NMR spectroscopy, ESI+ mass spectrometry, or its diagnostic chemical reduction to the yellow derivative bilirubin. A small-scale variant of this extraction requires only a single 3 h lab period, and the extracts can be analyzed by UV–vis spectroscopy, ESI+ MS, or HPLC. An introduction to the biological origin of biliverdin is provided. This pedagogically flexible project combines natural product isolation with the spectroscopic characterization of a multifunctional biomedically important compound and touches upon many aspects of chemistry and biology. The colorful experimen...

Carnauba and Rhea Americana Eggshell Powder Incorporation in PHB Bionanocomposites

In this work PHB poly (3-hydroxybutyrate) bionanocomposites with carnauba or emu eggshells (rhea americana), in amounts of 1 to 3 % wt%, were obtained by solution intercalation. Neat PHB solutions were prepared at room temperature under constant stirring for 3 hours and at rest 24 hours. The solution was then heated to 80°C and stirred for 3 hours before filler addition. Polymeric films were obtained by casting and solvent evaporation at room temperature. The filler were characterized by X-ray diffraction and thermal analysis and the films were characterized by X-ray diffraction, scanning electron and optical microscopies. System morphology was dependent on filler identity.

Obtainment of Spherical-Shaped Calcite Crystals Induced by Intramineral Proteins Isolated from Eggshells of Ostrich and Emu

In this work, we have performed a set of experiments to study how intramineral proteins affected the growth of calcite crystals and induced spherical growth. Intramineral proteins were first isolated from ostrich and emu eggshells and then purified by liquid chromatography. Samples of these proteins were analyzed by means of cyclic voltammetry to check their selectivity for carbonate ions. Then they underwent assays in solution through dynamic light scattering (DLS) to help us establish their homogeneity and stability (whether individually or in pairs) in the presence of carbonate ions. This was followed by in vitro crystallization experiments to determine how they affected the morphology of calcite crystals interacting with the intramineral proteins. Finally, scanning electron microscopy (SEM) showed that the morphology of the calcite crystals was strongly modified in the presence of these intramineral proteins.

Ultrastructure of the eggshell of selected Palaeognathae species – a comparative analysis

AbstractThe study aimed at comparative analysis of the eggshell ultrastructure, indicating differences and similarities in its structure depending on the bird species. The study was carried out in ostrich, emu and rhea breeding flocks. The birds were kept under open system. The ostrich flock comprised 6 females and 3 males, the emu flock included 22 birds with equal sex ratio, while the rhea flock consisted of 16 females and 4 males. Emus and rheas were 5 years old and in their 3rd laying year, whereas ostriches were 4 years old and in their 2nd laying year. The analysis of eggshell ultrastructure and porosity was performed on the post-hatching eggshells being obtained after the incubation of eggs from around peak laying period of these birds. In total, 27 eggshells were evaluated, 9 of each species. Analysis of the ultrastructure of ostrich, emu and rhea eggshells showed their different architecture being dependent on the bird species. The cuticle in ostrich eggs adhered firmly to the vertical crystal layer, it mainly occurred around pore canal orifices in rhea eggs, while only its residual presence was observed in emu eggs. The percentage of the vertical crystal layer was similar in the ostrich and rhea eggshells (2-3%) but significantly higher in the emu eggshells (9%). The largest number of mammillae per unit of inner eggshell surface area was recorded in emus, while the broadest palisades in rheas. The ostrich eggshells were shown to be characterised by the least number of pores per unit of surface area, with significantly narrower pore canals.

Did central Australian megafaunal extinction coincide with abrupt ecosystem collapse or gradual climate change?

ABSTRACTAim In central Australia, the giant flightless bird Genyornis newtoni disappeared about 45–50 thousand years ago (ka). It has been reported that coincident with this extinction the carbon isotopic composition of preserved eggshells of the extant emu (Dromaius novaehollandiae) shows an abrupt dietary shift from tropical grasses (C4 photosynthesis) to temperate grasses and/or woody browse (C3 photosynthesis). This abrupt shift has been interpreted as signalling ‘ecosystem collapse’ due to landscape burning by humans. We evaluate an alternative interpretation, that the shift in diet was not abrupt, but gradual, and caused by the weakening of the Australian monsoon.Location Lake Eyre, central Australia.Methods We re‐analysed a large, published dataset of emu diet δ13C (inferred from δ13C of preserved eggshells) spanning the last 140,000 years, using time‐series analysis. Using Akaike's information criterion, we compared two contrasting models: (1) there was an abrupt shift in δ13C coincident with the extinction of Genyornis, assumed 47.5 ka; and (2) there was a gradual shift in δ13C, correlated with reconstructed water level in Lake Eyre, a proxy for monsoon intensity.Results There was little evidence of an abrupt shift in emu diet δ13C about 45–50 ka, but δ13C appeared to steadily decrease between about 80 and 30 ka. Indeed, the model representing a correlation between δ13C and lake level was more than seven times more likely than the model representing an abrupt shift at 47.5 ka.Main conclusions The emu eggshell isotopic record from Lake Eyre does not support the hypothesis that landscape burning by humans transformed a savanna−grassland mosaic into the modern desert scrub, contributing to the extinction of Genyornis. While our findings cast strong doubt on the foremost line of evidence that landscape burning by humans caused the megafaunal extinctions, and suggest that central Australia was becoming increasingly arid in the Late Pleistocene, the relative roles of hunting by humans and climate change in the megafaunal extinctions remain unresolved.

Carbon isotope evidence for an abrupt reduction in grasses coincident with European settlement of Lake Eyre, South Australia

Stable carbon isotopes in emu eggshell (EES) reflect emu diets and consequently the vegetation available for food sources. At Lake Eyre, South Australia, isotopic data suggest that there has been a rapid and dramatic change in vegetation at some point over the last 200 years when compared with the rest of the Holocene. The proportion of C4 plants in emu diets has been reduced by approximately 20% in response to an overall shift in C4/C3 biomass at Lake Eyre. Isotopic measurement of the dominant plants at Lake Eyre indicate that the C4 plants are almost entirely comprised of grasses and some chenopods and the C3 plants are comprised of the dominant chenopods, shrubs, trees and forbs. We surmise that the -20% reduction in C4 plant biomass reflects landscape degradation and loss of C4 grasses resulting from a combination of effects, including overgrazing by both introduced (e.g., sheep, cattle and rabbits) and native (e.g., kangaroos) animals, increasing drought and a change in fire regime beginning in the late 1890s. The magnitude of vegetation change that occurred in the last 200 years is as great as that which occurred during the last glacial maximum (-21 000 years ago), and provides the first evidence for major environmental change at Lake Eyre soon after Europeans settled the arid zone.

Early Human Occupation at Devil's Lair, Southwestern Australia 50,000 Years Ago

New dating confirms that people occupied the Australian continent before the earliest time inferred from conventional radiocarbon analysis. Many of the new ages were obtained by accelerator mass spectrometry 14C dating after an acid–base–acid pretreatment with bulk combustion (ABA-BC) or after a newly developed acid–base–wet oxidation pretreatment with stepped combustion (ABOX-SC). The samples (charcoal) came from the earliest occupation levels of the Devil's Lair site in southwestern Western Australia. Initial occupation of this site was previously dated 35,000 14C yr B.P. Whereas the ABA-BC ages are indistinguishable from background beyond 42,000 14C yr B.P., the ABOX-SC ages are in stratigraphic order to ∼55,000 14C yr B.P. The ABOX-SC chronology suggests that people were in the area by 48,000 cal yr B.P. Optically stimulated luminescence (OSL), electron spin resonance (ESR) ages, U-series dating of flowstones, and 14C dating of emu eggshell carbonate are in agreement with the ABOX-SC 14C chronology. These results, based on four independent techniques, reinforce arguments for early colonization of the Australian continent.

Alternative timescales: a critical review of Willandra Lakes dating

AbstractThe Late Pleistocene radiocarbon record from the Willandra Lakes region is analysed to select the most reliable age estimates. Chemical pretreatment experiments addressing problems of contradictory ages on black organic samples from archaeological hearths and shell middens show that macroscopic charcoal is not present at some sites, although multiple sub‐samples of well preserved charcoal have been dated at other sites. Radiocarbon measurements on properly decontaminated charcoal are as reliable as other robust single component samples such as shell, fish otoliths and emu eggshell. After calibration, 14C ages are in close agreement with luminescence based ages on suitably analysed quartz from the same sites. Regional patterns of 14C and luminescence dates are correlated across the Murray‐Darling basin, implying rapid and sensitive responses to changing climate. Chemical arguments, and the likelihood of widespread sediment erosion prior to Last Glacial Maximum, suggest that probable ages for some human burials are younger than usually quoted. There is no unequivocal evidence for archaeological remains in the Willandra older than 43 ka.

Session serves up smorgasbord of paleoclimatic research

At the Western Pacific Geophysics Meeting held in July 1996 in Brisbane, Australia, a session titled “Glacial/Interglacial Records of the PEP Transects” brought together scientists interested in applying their range of expertise to interdisciplinary endeavors. For example, where else could one learn of progress in quantifying paleo‐precipitation by using magnetic climofunctions, or how to obtain paleo‐temperature from racemization measurements on ancient emu eggshells, or how to determine changes in the volume of the oceans from U‐series ages on fossil reefs?

Low-latitude glacial cooling in the Southern Hemisphere from amino-acid racemization in emu eggshells

The record of natural climate variability over glacial-interglacial timescales provides a framework from which a better mechanistic understanding of the climate system may be derived. But this approach is limited by the number and distribution of well-dated and reliable palaeoenvironmental archives. Particularly vexing is the conflicting evidence for low-latitude cooling during the Last Glacial Maximum, and the apparent synchrony in glacial activity between the hemispheres despite out-of-phase insolation forcing1–4. Here we utilize the temperature-dependent amino acid racemization reaction in radiocarbon-dated emu eggshell fragments from the continental interior of Australia to reconstruct low-altitude subtropical temperatures for the past 45 kyr. Racemization rate-changes indicate that millennial-scale average air temperatures were at least 9 °C lower between 45 and 16 kyr BP than since 16 kyr BP. A temperature change of this magnitude, coupled with other low-latitude palaeotemperature records that indicate substantial cooling3,4, must reflect global processes, which, we speculate, involved glacial-age reduction in atmospheric water vapour content.

The pore arrangement in the emu (Dromaius novæhollandiæ) eggshell as shown by plastic models

SUMMARYPores arising in the cone layer merge with a plexus of tubules running just under and parallel to the outer surface of the emu eggshell. The outer surface of the shell is irregular due to dark green crystalline material arranged as flat domes. The plexus of tubules vent to the ambient environment via short pores opening in the valleys between these domes.