Researchers document aviary eggshell with iridescence for the first time

December 10, 2014 by Bob Yirka, Phys.org report
Photographs (a–c) of T. major, E. elegans and N. maculosa nests. Average length breadth of eggs (a–c): 58 48 mm, 53 39 mm and 40 29 mm. Photo credits: Karsten Thomsen, Sam Houston and Shirley Sekarajasingham. Journal of the Royal Society Interface, Published 10 December 2014 . DOI: 10.1098/rsif.2014.1210

(Phys.org)—A team of researchers with members from New Zealand, Czech Republic and the U.S. has documented for the first time an example of an aviary egg that has iridescence. In their paper published in Journal of the Royal Society Interface, the team describes their study of eggs laid by great tinamou, which revealed the nature of the egg coloring.

Bird come in a wide variety of colors, which scientists suspect is nature's way of keeping them hidden so that other animals won't come along and eat them. Prior research has found that most egg coloring is due to just two different pigments. In this new study, the researchers took a closer look at the shiny blue eggs laid by great tinamou, better known in Central and South America, where they live, as "mountain hen."

In investigating the eggs, the researchers found that they were iridescent—they look to be different colors depending on the angle they are viewed from—a first for an avian . That got the researchers wondering about the source of the iridescence. Close examination showed that the eggs were covered with a smooth cuticle (which they found to be made of calcium phosphate, calcium carbonate, and some other yet to be identified organic compounds) which gave the egg its glossy sheen. When they removed the cuticle from a portion of an egg sample—they found that it was blue underneath, but that the iridescence was gone. Thus, they concluded that the iridescent blue was due to a combination of the pigment and cuticle.

The researchers can't say for sure why the bird eggs have such features as they would appear to draw attention to them, rather than help keep them hidden. It seems possible that the actually causes the eggs to be more difficult to see in their particular environment to a particular type of prey. More likely, the researchers suggest is that eggs that stand out can be more easily spotted or differentiated from other eggs from birds of the same species, which could serve as a means of encouraging males to assist with incubation.

From left to right: eggs of the great tinamou (Tinamus major), elegant crested tinamou (Eudromia elegans), and spotted nothura (Nothura maculosa). Credit: Photograph of great tinamou egg (UMMZ 191600) used with permission from the University of Michigan Museum of Zoology. Photo credits: D. Hanley (great tinamou) and M. Hauber (elegant crested tinamou and spotted nothura).

Explore further: Bad parenting could give zebra finches the evolutionary edge

More information: A nanostructural basis for gloss of avian eggshells, Journal of the Royal Society Interface, Published 10 December 2014 . DOI: 10.1098/rsif.2014.1210

ABSTRACT

The role of pigments in generating the colour and maculation of birds' eggs is well characterized, whereas the effects of the eggshell's nanostructure on the visual appearance of eggs are little studied. Here, we examined the nanostructural basis of glossiness of tinamou eggs. Tinamou eggs are well known for their glossy appearance, but the underlying mechanism responsible for this optical effect is unclear. Using experimental manipulations in conjunction with angle-resolved spectrophotometry, scanning electron microscopy, atomic force microscopy and chemical analyses, we show that the glossy appearance of tinamou eggshells is produced by an extremely smooth cuticle, composed of calcium carbonate, calcium phosphate and, potentially, organic compounds such as proteins and pigments. Optical calculations corroborate surface smoothness as the main factor producing gloss. Furthermore, we reveal the presence of weak iridescence on eggs of the great tinamou (Tinamus major), an optical effect never previously documented for bird eggs. These data highlight the need for further exploration into the nanostructural mechanisms for the production of colour and other optical effects of avian eggshells.

Press release

Related Stories

Bad parenting could give zebra finches the evolutionary edge

December 1, 2014

Species must reproduce to survive, and animals have found unique ways of achieving this. For some, including us, it seems as though producing a few offspring that require extended care is the best strategy. For others, such ...

Researchers identify molecule that protects women's eggs

October 7, 2014

A new study led by Professor Kui Liu at the University of Gothenburg has identified the key molecule 'Greatwall kinase' which protects women's eggs against problems that can arise during the maturation process.

Recommended for you

Why don't turtles still have tail spikes?

January 17, 2018

We're all familiar with those awesome armored giants of the Jurassic and Cretaceous periods - Stegosaurus and Ankylosaurus - and their amazing, weaponized tails. But why aren't similar weaponized tails found in animals living ...

6 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

katesisco
not rated yet Dec 10, 2014
or it could just be a wild card from Mother Nature, a roll of the dice to see what happens.
betterexists
1 / 5 (2) Dec 10, 2014
Can Dinosaur-Sized Birds be Produced? Can They Be?
..YES....YES..... YES....YES..... YES....YES..... YES....YES... YES....YES....YES.....YES.......!
WHY? WHY? WHY? WHY? WHY? /// WHY? WHY? WHY? .WHY? .WHY? WHY?
BECAUSE ALL do Start in Cell Sized Zygotes- Just as All Oceans & Mountains do also Start in Tiny Size..The Atoms!

SO, with proper preparations, ORDINARY Tiny Egg Size Does SUFFICE to start with unlike the Tiny Mammalian Wombs.
Simply Provide Far more Similar factory made Shells around from time to time; Just Sandwich More & More Suitable Fluid Nutrients in between those series of Shells.
Let That Giant grow & grow & then FINALLY HATCH & FLY INTO A SPIDER SILK or Stronger (Certainly Not Steel) CAGE for Research Purposes.
Forget the Mammoths! We already have those Elephants. They are of Secondary importance.
betterexists
1 / 5 (2) Dec 10, 2014

It is NOT that those Innocent Mom Birds wanted Iridiscence for their Eggs NOR was ordered by th(at/ose) Stupid God(s) but that an Accidental DNA Mutation Sure did it all....It then might have helped in its species' greater & greater Survival.....Similar to your Powerball Lottery Win ensuring your greater & greater Economic Freedom from labor!
Greater Animal Size might have favored the Giant Dinosaurs in their survival but Fresh water was always LIMITED...unless they had loved to drink Sea Water...which I doubt 100% They might have roamed around the River shores like those early human settlers, but For How Long? Question: God does not have anything else to do? To Create & Remove! Utter Stupidity.
thewhitelilyblog
1 / 5 (1) Dec 11, 2014
I think it's like this: predator is nosing around, flies by. "Is that a ___ egg?" it asks. Then the iridescence kicks in: "No, it's not. I was wrong. Moving on."

This is true in human discourse that means to deceive. It is necessary to confuse almost every reader only for a second, and the lie can be continued undetected. This is a great art, fully utilized at Vatican II, still developing in our high-jacked Church, as at the recent Synod on the family. Just be confusing. Must work in nature, as in society.
betterexists
not rated yet Dec 11, 2014
Chickens and turkeys 'closer to dinosaur ancestors' than other birds. New research from the University of Kent suggests that chickens and turkeys have experienced fewer gross genomic changes than other birds.
katesisco
not rated yet Dec 23, 2014
Thinking more:
Science says the iridescence is due to " (you wont believe this) smoothness at the nanoscale. The small creature is so lightly stressed that extra protein goes into iridescence. One suspect that this is due to the male's exclusive egg hatching. One wonders what the female stress level would be if she could not find appropriate nest sites? And if a female high stress level would produce less iridescence?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.