An international team of researchers has reconstructed a song played by a prehistoric bushcricket some 165 million years ago.
A modern-day bushcricket (Jackins)
In the Jurassic the world was host to a diversity of sounds. Primitive bushcrickets and croaking amphibians were among the first animals to produce loud sounds by rubbing certain body parts together.
Modern-day bushcrickets – also known as katydids – produce mating calls by rubbing a row of teeth on one wing against a plectrum on the other wing. But how their primitive ancestors produced sound and what their songs actually sounded like was unknown – until now.
Chinese paleontologists, including Jun-Jie Gu and Prof. Dong Ren from the Capital Normal University in Beijing, recently discovered an exceptionally detailed bushcricket fossil from the Mid Jurassic period and provided it to their colleagues – Dr. Fernando Montealegre-Zapata and Prof. Daniel Robert, both experts in the biomechanics of singing and hearing in insects at the University of Bristol.
According to the University of Bristol, the specimen had such well-preserved wing features that the details of its stridulating organs were clearly visible under an optical microscope.
It was identified as a new fossil species and named Archaboilus musicus by the team.
Dr Montealegre-Zapata and Prof. Robert examined the anatomical construction of the fossil’s song apparatus, and compared it to 59 living bushcricket species. They concluded that this animal must have produced musical songs, broadcasting pure, single frequencies.
In the study, published yesterday in the Proceedings of the National Academy of Sciences, the researchers reveal that this prehistoric species of bushcricket radiated musical songs using a resonant mechanism tuned at a specific frequency.
Fossilized specimen of Archaboilus musicus: red arrows show the location of bushcricket’s song apparatus (Fernando Montealegre-Zapata et al)
“This discovery indicates that pure tone communication was already exploited by animals in the middle Jurassic, some 165 million years ago,” Prof. Robert said. “For Archaboilus, as for living bushcricket species, singing constitutes a key component of mate attraction. Singing loud and clear advertises the presence, location and quality of the singer, a message that females choose to respond to – or not. Using a single tone, the male’s call carries further and better, and therefore is likely to serenade more females. However, it also makes the male more conspicuous to predators if they have also evolved ears to eavesdrop on these mating calls.”
Dr. Montealegre- Zapata established that A. musicus sang a tone pitched at 6.4kHz and that every bout of singing lasted 16 milliseconds.
This turned out to be enough information to acoustically reconstruct the song itself, possibly the most ancient known musical song documented to date.
“Using a low-pitched song, A. musicus was acoustically adapted to long-distance communication in a lightly cluttered environment, such as a Jurassic forest,” Dr. Montealegre- Zapata said. “Today, all species of katydids that use musical calls are nocturnal so musical calls in the Jurassic were also most likely an adaptation to nocturnal life. Being nocturnal, A. musicus probably escaped from diurnal predators like Archaeopterix, but it cannot be ruled out that Jurassic insectivorous mammals like Morganucodon and Dryolestes also listened to the calls of Archaboilus and preyed on them.”
“This Jurassic bushcricket thus sheds light on the potential auditory capacity of other animals, and helps us learn a little more about the ambiance of a world long gone. It also suggests the evolutionary mechanisms that drove modern bushcrickets to develop ultrasonic signals for sexual pairing and for avoiding an increasingly relevant echolocating predator, but that only happened 100 million years later, possibly with the appearance of bats,” the researcher concluded.
