Fossils with an amber coating shine light on the evolution of bioluminescent insects

Trapped in amber for ~ 100 million years, a well-preserved beetle sheds light on the proliferation of bioluminescent beetles in the Cretaceous period and provides the lost fossil link between relatives live fireflies.

With more than 3,500 species described, beetles that make light up are the most diverse terrestrial animals. Fireflies, fire beetles, worm beetles and their relatives use light to keep predators away, attract mates, and some females even use it to attract insecure males to eat. Historically, despite their diversity, the evolution of bioluminescence in beetles has not been well understood.

“Most light-producing beetles are soft-bodied and very small, so they have a scarce fossil record. However, this new fossil, found in amber from the head of north of Myanmar, well preserved, even the light organ on her abdomen, ”said Dr Chenyang Cai, a researcher at Bristol University and associate professor at NIGPAS.

The presence of a light organ on the male abdomen provides direct evidence that Cretophengodes were able to produce light to adults, about 100 million years ago.

“The recently discovered fossil, preserved by life-like fidelity in amber, represents an extinct relative and the living families of Rhagophthalmidae and Phengodidae,” said Yan-Da Li of the Institute Nanjing Geology and Palaeontology (NIGP) and Peking University in China.

Most light-making beetles fall into the very surface of Elateroidea with about 24 thousand known species and thousands more waiting to be defined. Find this beetle, published in the Proceedings of the Royal Society B., providing the required fossil link between living families and in doing so scientists understand how these beetles evolved and how they should be classified.

“Elateroidea is one of the most heterogeneous groups of beetles and that has been very difficult for entomologists to deal with, especially as important anatomical techniques have many times grown independently in non-native groups. The discovery of an extinct elateroid beet family is important because it helps shed light on the evolution of these fascinating beetles, “said Erik Tihelka of the School of Earth Sciences.

“We believe that light production first developed in the soft and vulnerable larvae of the beetle as a means of protection to keep predators away. The fossil shows that the Cretaceous light product was brought up by It could also be a complement to choosing to attend other activities such as making friends, ”says Robin Kundrata, an expert on elateroid beetles from Palacký University in the Czech Republic. .

Light-producing beetles often have unusual changes. One of the most impressive is that the females often do not look anything like their male peers and instead retain many of the larval characteristics of the adults.

“A good example of this is the trilobite beetle, where the females do not resemble beetles at all and instead resemble trilobites. This means that females often get over it when they hatch. We want to focus on these rare beetles when studying the fossil record in the coming years, “said Yan-Da Li.

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The study was supported by the National Science Foundation and Chinese Academy of Sciences.

Paper:

‘Cretophengodidae, a new Cretaceous beetle family sheds light on the evolution of bioluminescence,’ by Yan-Da Li, Robin Kundrata, Erik Tihelka, Zhenhua Liu, Diying Huang and Chenyang Cai, published in Proceedings of the Royal Society B.. DOI: 10.1098 / rspb.2020.2730