old fossil beetle preserved in Burmese amber from the age of dinosaurs. The well-preserved body of this distant relative of modern fireflies has provided researchers with a unique insight into the evolution of communication systems in bioluminescent beetles and their relatives. The newly described species, Icaroramus perisi, possessed a light-producing organ on its abdomen as well as extraordinarily complex antennae that probably functioned as a kind of chemical radar. The results of the research were published in the prestigious journal Proceedings of the Royal Society B.
“This fossil beetle is remarkable because it combines two forms of communication that are central to modern fireflies and their relatives: chemical signals and light. Thanks to its exceptional preservation in amber, we can study such an unusual combination of traits deep in evolutionary time,” says Yan-Da Li, lead author of the study.
The antennae revealed exceptional sensory equipment
The new species of bioluminescent beetle was found in Burmese amber, which preserves extremely fine anatomical details of insects from the mid-Cretaceous. This allowed the researchers to study not only the overall body shape, but also the complex structure of the antennae and the abdominal structures.
The antennae of the new beetle have 12 segments, most of which bear two morphologically distinct pairs of long branches. Such an antennal structure has not previously been known in any living or fossil beetle. According to the authors, these antennae probably greatly increased the sensory surface area and enabled highly sensitive detection of chemical signals, especially sex pheromones.
Pheromones for courtship, light for defence
“In modern fireflies and related groups, we often see a close link between the shape of the antennae and the way species communicate. Males of species that rely on pheromones frequently have elaborately branched antennae capable of detecting even very faint chemical signals. In Icaroramus perisi, this specialization reached an extraordinary level,” explains Robin Kundrata from the Department of Zoology at the Faculty of Science.
Interestingly, Icaroramus perisi also had a structure on its abdomen that the researchers interpret as a light-producing organ. However, this does not necessarily mean that light was used primarily in courtship, as it is in many modern fireflies. The authors suggest that mate location may have been mediated mainly by pheromones, while bioluminescence may have served instead as a warning signal to predators. A similar function of light is also known in some living bioluminescent beetles.
The fossil changes our view of the evolution of bioluminescence
“The discovery shows that the evolution of bioluminescence was not a simple story leading directly to modern fireflies. In the early evolution of this group, light may have served primarily as a warning, antipredatory signal and was only later recruited for sexual communication in some lineages. This fossil therefore reveals an evolutionary experiment that has no exact counterpart today,” says Chenyang Cai, co-author of the study.
The study was published in Proceedings of the Royal Society B under the title “A firefly relative that smelled and glowed: evidence for complex signalling systems in Cretaceous lampyroids”. It is part of long-term research into fossil and living elateroid beetles carried out by the team of Robin Kundrata at Palacký University Olomouc.