Detecting pigments from colourful eggshells of extinct birds

Abstract

The known chemical basis of diverse avian eggshell coloration is generated by the same two classes of tetrapyrrole pigments in most living birds. We aimed to extend the evolutionary scope of these patterns by detecting pigments from extinct birds' eggs. In our samples biliverdin was successfully extracted from subfossil shell fragments of the blue-green egg-laying upland moa Megalapteryx didinus, while protoporphyrin was extracted from the beige eggs of two other extinct moa species. Our data on pigment detection from eggshells of other extant paleognath birds, together with published information on other modern lineages, confirm tetrapyrroles as ubiquitous and conserved pigments contributing to diverse eggshell colours throughout avian evolution.

Analysing avian eggshell pigments with Raman spectroscopy

“…The pigment in two blue eggshell fragments from upland moa Megalapteryx didinus had previously been identified as biliverdin using destructive techniques (Igic et al, 2010). Here, we also identified biliverdin in upland moa eggshell fragments with nondestructive Raman spectroscopy (Fig.…”

“…Sulphuric acid extraction of eggshell pigments and subsequent mass spectrometry were performed on eggshell fragments from domestic chicken, emu, elegant crested tinamou, great tinamou and Japanese quail, following protocols described in Igic et al (2010). Eggshell samples were acquired as above, but were not the same eggshells used for Raman spectroscopy.…”

“…Protoporphyrin eggshell pigmentation has also been of recent research interest for a variety of adaptive functions (Cassey et al, 2011). To date, the identification and quantification of pigments and their concentrations have required destructive methods (Kennedy and Vevers, 1976;Igic et al, 2010Igic et al, , 2012. This is particularly unfeasible for extensive studies of unique museum specimens, where the majority of eggshell samples are deposited and preserved (Hauber, 2014).…”

“…Chemically confirming the types of pigment in particular eggshells or mapping the distributions of pigments across an eggshell surface are routine research objectives for which a nondestructive technique would be ideal. Raman spectroscopy easily satisfies this analytical niche and requires relatively few methodological considerations for routine analyses of even rare and irreplaceable materials, including the eggs of extinct bird species (Igic et al, 2010).…”

Twenty-first century advances in knowledge of the biology of moa (Aves: Dinornithiformes): a new morphological analysis and moa diagnoses revised

“…Igic et al (2010) found that the pigment biliverdin is responsible for the blue-green colour in shell fragments of M. didinus, while protoporphyrin was found in the beige eggs of two other moa species.…”