Hearing has evolved independently many times in the animal kingdom and is prominent in various insects and vertebrates for communication and predator detection. Among insects, katydid ears are unique, as they have evolved outer, middle, and inner ear components, analogous in their biophysical principles to the mammalian ear. In new research, paleontologists from the University of Lincoln and elsewhere reconstructed the geometries of the outer ear components and wings of Eomortoniellus handlirschi, an exceptionally well-preserved katydid fossilized in a piece of 44-million-year-old Baltic amber. They found that Eomortoniellus handlirschi was communicating at a peak frequency of 32 kHz and demonstrated that the ear was biophysically tuned to this signal and to providing hearing at higher-frequency ultrasounds (over 80 kHz), likely for enhanced predator detection. The results indicate that the evolution of the unique ear of the katydid, with its broadband ultrasonic sensitivity and analogous biophysical properties to the ears of mammals, emerged in the Eocene epoch.
Around 44 million years ago, an adult male of Eomortoniellus handlirschi became stuck in pine tree resin, which hardened encasing the bug.
The amber specimen was uncovered in 1936 in an area then known as East Prussia, Germany.
CT scans of the insect revealed that the sap had got into the katydid’s ear canal, located on the inside of its legs.
With the sap inside, the delicate structure of the insect’s ear was well-preserved.
“This discovery wouldn’t have been possible without such a well-preserved katydid, which highlights how important museum collections are in discovering specimens like these,” said Dr. Charlie Woodrow, a former Ph.D. student at the University of Lincoln who is now a researcher at Uppsala University.
“This katydid was frozen in time at a crucial moment in the arms race between echolocating predators and insects.”
“Shortly before this animal was fossilized, bats…
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