Trapped in amber for 99 million years, an exceptionally well-preserved light-producing beetle sheds light on the diversification of bioluminescent insects in the Cretaceous.
With over 3,500 species described, light-producing beetles are the most diverse bioluminescent terrestrial animals. Fireflies, beetles, beetles and their relatives use light to repel predators, attract pairs, and some females even use light to attract males who do not suspect to eat. From a historical point of view, despite its diversity, the evolution of bioluminescence in beetles has been poorly understood.
“Most light-producing beetles are soft-bodied and quite small, so they have few fossil recordings. However, this new fossil, found in amber in northern Myanmar, is exceptionally well preserved, including the light organ in the abdomen is intact.” , explains Dr. Chenyang Cai, a researcher at the University of Bristol and an associate professor at NIGPAS.
The presence of a light organ in the male abdomen provides direct evidence that Cretophengodes adults were able to produce light about 100 million years ago.
The newly discovered fossil, preserved with real fidelity in amber, is a missing relative of the firefly and the living families “Rhagophthalmidae” and “Phengodidae”, notes Yan-Da Li of the Nanjing Institute of Geology and Paleontology (NIGP)) and the University Beijing from China.
Most light-producing beetles belong to the giant superfamily Elateroidea, with about 24,000 known species and thousands more waiting to be described. The discovery of this beetle provides the missing fossil link between living families and, in doing so, helps scientists understand how these beetles evolved and how they should be classified.
“Elateroidea is one of the most heterogeneous groups of beetles and this has always been very difficult for entomologists to manage, especially since important anatomical innovations have often evolved independently in unrelated groups. The discovery of a new family of extinct Elateroid beetles is significant because it helps to shed light on the evolution of these fascinating beetles, “explains Erik Tihelka of the Faculty of Earth Sciences.
“We believe that light production initially evolved in the soft and vulnerable larvae of the beetle as a defensive mechanism to protect itself from predators. The fossil shows that in the Cretaceous, light production was also absorbed by adults. It could have been co-opted to perform other functions such as mating, “says Robin Kundrata, an expert in Elateroid cockroaches at Palacky University in the Czech Republic.
Light beetles often have unusual adaptations. One of the most surprising is that females often do not resemble their male counterparts and instead retain many larval features in adulthood.
“A good example of this is the trilobite beetle, where females do not look like beetles at all and instead look superficially like trilobites. This means that females are often overlooked when collecting in the field. We want to focus on these beetles. unusual when looking for fossil records in the next few years, “said Yan-Da Li.
The paper is published in the Proceedings of the Royal Society B.