Fossilized beetles are redder than they were in life

Sep 29, 2011 by Deborah Braconnier report
Image credit: Maria McNamara

(PhysOrg.com) -- A new study published in the journal Proceedings of the Royal Society B shows that the colors of fossilized beetles do not represent the colors they sported in life. From what researchers can determine, the fossilization process shifted the colors toward the red end of the spectrum.

Maria McNamara, a postdoctoral research fellow from the Department of Geology and Geophysics at Yale led the research. She and her team examined the fossilized remains of a variety of beetle dating from 15 to 47 million years ago. The beetles had lived in what are now Idaho and Germany, as well as a few other locations.

Using a and a , the researchers examined the beetle’s exoskeleton. The fine layers that make up the exoskeleton and the way these layers bend and reflect light is what is responsible for the magnificent colors seen in these beetles. Using the microscopes, the team determined that the process of fossilization had changed the chemistry in the exoskeleton structure and altered its refractive index. This change caused the colors to redshift, so brightly violet beetle from millions of years ago would appear blue in a fossilized form just as a bright yellow beetle would now appear more orange.

The researchers point out that this new information will allow them to determine the true color of these insects and give them evidence of the evolution of structural color. McNamara explains that colors have a variety of functions and may play a role in communication or thermoregulation, so identifying the true color of the insects can help them better understand what the colors were used for.

While the researchers saw this redshift in the beetles they examined, they do caution that the level of redshift differed slightly between specimens. The beetles they examined also came from similar lake sediment and they suggest that other sediment may also alter the changes seen.

While this study was done on , the hope is it can now be used to help determine the original in other insects such as butterflies and dragonflies.

Explore further: 110-million-year-old crustacean holds essential piece to evolutionary puzzle

More information: The original colours of fossil beetles, Proceedings of the Royal Society B, Published online before print September 28, 2011, doi: 10.1098/rspb.2011.1677

Abstract
Structural colours, the most intense, reflective and pure colours in nature, are generated when light is scattered by complex nanostructures. Metallic structural colours are widespread among modern insects and can be preserved in their fossil counterparts, but it is unclear whether the colours have been altered during fossilization, and whether the absence of colours is always real. To resolve these issues, we investigated fossil beetles from five Cenozoic biotas. Metallic colours in these specimens are generated by an epicuticular multi-layer reflector; the fidelity of its preservation correlates with that of other key cuticular ultrastructures. Where these other ultrastructures are well preserved in non-metallic fossil specimens, we can infer that the original cuticle lacked a multi-layer reflector; its absence in the fossil is not a preservational artefact. Reconstructions of the original colours of the fossils based on the structure of the multi-layer reflector show that the preserved colours are offset systematically to longer wavelengths; this probably reflects alteration of the refractive index of the epicuticle during fossilization. These findings will allow the former presence, and original hue, of metallic structural colours to be identified in diverse fossil insects, thus providing critical evidence of the evolution of structural colour in this group.

Related Stories

What scientists know about jewel beetle shimmer

Jul 23, 2009

"Jewel beetles" are widely known for their glossy external skeletons that appear to change colors as the angle of view changes. Now they may be known for something else--providing a blueprint for materials ...

Complex dynamics underlie bark beetle eruptions

Jun 02, 2008

Forest management that favors single tree species and climate change are just two of the critical factors making forests throughout western North America more susceptible to infestation by bark beetles, according to an article ...

Beetle dung helps forests recover from fire

Nov 29, 2007

Armed with a pair of tweezers and a handful of beetle droppings, University of Alberta forestry graduate Tyler Cobb has discovered why the bug-sized dung is so important to areas ravaged by fire.

Recommended for you

Fish eye sheds light on color vision

Dec 23, 2014

A fish eye from a primitive time when Earth was but one single continent, has yielded evidence of color vision dating back at least 300 million years, researchers said Tuesday.

Study sheds new light on the diet of extinct animals

Dec 22, 2014

A study of tooth enamel in mammals living today in the equatorial forest of Gabon could ultimately shed light on the diet of long extinct animals, according to new research from the University of Bristol.

User comments : 0

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.