Monday, June 21, 2021

Amber Fossils Unlock True Color of 99-Million-Year-Old Insects

Nature is full of colors, from the radiant shine of a peacock’s feathers or the bright warning coloration of toxic frogs to the pearl-white camouflage of polar bears. Usually, fine structural detail necessary for the conservation of color is rarely preserved in the fossil record, making most reconstructions of the fossil based on an artist’s imagination. A research team from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has now unlocked the secrets of true coloration in 99-million-year-old insects.

Colors offer many clues about the behavior and ecology of animals. They function to keep organisms safe from predators, at the right temperature, or attractive to potential mates. Understanding the coloration of long-extinct animals can help us shed light on ecosystems in the deep geological past. The study, published in Proceedings of the Royal Society B, offers a new perspective on the often overlooked, but by no means, dull lives of insects that co-existed alongside dinosaurs in Cretaceous rainforests.

Diverse structural-colored insects in mid-Cretaceous amber from northern Myanmar. (Image: by NIGPAS)

Researchers gathered a treasure trove of 35 amber pieces with exquisitely preserved insects from an amber mine in northern Myanmar. Dr. CAI Chenyang, associate professor at NIGPAS who led the study, said:

The rare set of amber fossils includes cuckoo wasps with metallic bluish-green, yellowish-green, purplish-blue, or green colors on the head, thorax, abdomen, and legs. In terms of color, they are almost the same as cuckoo wasps that live today, said Dr. CAI. The researchers also discovered blue and purple beetle specimens and a metallic dark-green soldier fly. “We have seen thousands of amber fossils but the preservation of color in these specimens is extraordinary,” said Prof. HUANG Diying from NIGPAS, a co-author of the study. Prof. PAN Yanhong from NIGPAS, a specialist on palaeocolor reconstruction, explained saying:

To understand how and why color is preserved in some amber fossils but not in others, and whether the colors seen in fossils are the same as the ones insects paraded more than 99 million years ago, the researchers used a diamond knife blade to cut through the exoskeleton of two of the colorful amber wasps and a sample of normal dull cuticle. Using electron microscopy, they were able to show that colorful amber fossils have a well-preserved exoskeleton nanostructure that scatters light.

Comparisons between original and altered metallic colors in cleptine wasps. (Image: by NIGPAS)

The unaltered nanostructure of colored insects suggested that the colors preserved in amber may be the same as the ones displayed by them in the Cretaceous. But in fossils that do not preserve color, the cuticular structures are badly damaged, explaining their brown-black appearance. What kind of information can we learn about the lives of ancient insects from their color? Extant cuckoo wasps are, as their name suggests, parasites that lay their eggs into the nests of unrelated bees and wasps.

Structural coloration has been shown to serve as camouflage in insects, and so it is probable that the color of Cretaceous cuckoo wasps represented an adaptation to avoid detection. “At the moment we also cannot rule out the possibility that the colors played other roles besides camouflage, such as thermoregulation,” adds Dr. CAI.

Provided by:  [Note: Materials may be edited for content and length.]

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.
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