Jurassic insect mating call brought to life
ADELAIDE: The musical mating call of a large 165-million-year-old winged insect called a katydid has been recreated after the discovery of an extraordinary fossil in Mongolia.
Katydids are nocturnal insects related to crickets and grasshoppers. They make loud mating calls by rubbing their wings together, in an action called stridulation. Sound is produced when a row of serrated teeth on one wing, called a file, moves across a scraper on the other wing like a guitar pick strumming across strings.
In Ningcheng County, Mongolia, palaeontologists have found a katydid fossil which displayed noise-producing structures along the wings. It is the oldest-known katydid fossil and reveals that these insects were producing musical calls as far back as the Jurassic Period.
"The fossil was so well-preserved that we could see all the tiny details of the stridulatory file. This was a very special formation," said Fernando Montealegre Zapata, entomologist from the University of Bristol in England, and co-author of the paper published today in the Proceedings of the National Academy of Science.
Lack of katydids in fossil record
Most modern-day katydids have asymmetrical wings that help them create very high frequency sounds outside the audible range for humans. Palaeontologists have long wondered about the evolution of sound production in katydid species, but the fossil record for this insect group is sparse. Until now, the oldest fossil was dated at 50 million years old.
Fossilised remains don't come with an audio recording. However, imprints of communication organs can provide clues about an animal's calls. In the Mongolian fossil, the teeth along the stridulatory files were exceptionally well-preserved. This offered a unique opportunity to reconstruct the calling sound of an extinct species.
The fossil also showed that the ancestors of modern katydids had symmetrical wings. Wing symmetry is associated with the production of pure, musical tones, so the team named the extinct species Archaboilus musicus.
Recreation of an ancient love song
Montealegre Zapata and his team examined the number of teeth along the stridulatory file in the fossil and compared them to the sound apparatus of 59 living katydid species. They used statistical models to determine the sound frequency and considered how wing symmetry affects sound radiation in order to predict how the animal was singing.
The scientists determined that A. musicus sang in low-frequency, musical tones at 6.4 kHz. This is effective for long distance communication close to the ground. It is also important for sound transmission in a noisy environment and the Jurassic forest would have been teeming with life, singing insects and the sounds of wind and waterfalls.
These songs would have allowed females to assess the quality and location of the singer and find a suitable mate. The results of this study also indicate that the female ear was already tremendously evolved 165 million years ago to be able to detect the musical tones of the serenading males.
"Scientists suspected that insects such as katydids have been using stridulation to produce musical songs for millions of years and now we have proof for it occurring in the mid-Jurassic," commented John Jennings, an entomologist from the University of Adelaide in South Australia.
Michael Keller, an entomologist also from the University of Adelaide in South Australia described the study as remarkable. "This research has given us a deeper appreciation of the behaviour of these insects in the forests of the Jurassic Period. We can also use these same methods to reconstruct other communication signals when other well-preserved fossils are found."
Katydids are nocturnal insects related to crickets and grasshoppers. They make loud mating calls by rubbing their wings together, in an action called stridulation. Sound is produced when a row of serrated teeth on one wing, called a file, moves across a scraper on the other wing like a guitar pick strumming across strings.
In Ningcheng County, Mongolia, palaeontologists have found a katydid fossil which displayed noise-producing structures along the wings. It is the oldest-known katydid fossil and reveals that these insects were producing musical calls as far back as the Jurassic Period.
"The fossil was so well-preserved that we could see all the tiny details of the stridulatory file. This was a very special formation," said Fernando Montealegre Zapata, entomologist from the University of Bristol in England, and co-author of the paper published today in the Proceedings of the National Academy of Science.
Lack of katydids in fossil record
Most modern-day katydids have asymmetrical wings that help them create very high frequency sounds outside the audible range for humans. Palaeontologists have long wondered about the evolution of sound production in katydid species, but the fossil record for this insect group is sparse. Until now, the oldest fossil was dated at 50 million years old.
Fossilised remains don't come with an audio recording. However, imprints of communication organs can provide clues about an animal's calls. In the Mongolian fossil, the teeth along the stridulatory files were exceptionally well-preserved. This offered a unique opportunity to reconstruct the calling sound of an extinct species.
The fossil also showed that the ancestors of modern katydids had symmetrical wings. Wing symmetry is associated with the production of pure, musical tones, so the team named the extinct species Archaboilus musicus.
Recreation of an ancient love song
Montealegre Zapata and his team examined the number of teeth along the stridulatory file in the fossil and compared them to the sound apparatus of 59 living katydid species. They used statistical models to determine the sound frequency and considered how wing symmetry affects sound radiation in order to predict how the animal was singing.
The scientists determined that A. musicus sang in low-frequency, musical tones at 6.4 kHz. This is effective for long distance communication close to the ground. It is also important for sound transmission in a noisy environment and the Jurassic forest would have been teeming with life, singing insects and the sounds of wind and waterfalls.
These songs would have allowed females to assess the quality and location of the singer and find a suitable mate. The results of this study also indicate that the female ear was already tremendously evolved 165 million years ago to be able to detect the musical tones of the serenading males.
"Scientists suspected that insects such as katydids have been using stridulation to produce musical songs for millions of years and now we have proof for it occurring in the mid-Jurassic," commented John Jennings, an entomologist from the University of Adelaide in South Australia.
Michael Keller, an entomologist also from the University of Adelaide in South Australia described the study as remarkable. "This research has given us a deeper appreciation of the behaviour of these insects in the forests of the Jurassic Period. We can also use these same methods to reconstruct other communication signals when other well-preserved fossils are found."
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