VOA标准英语2012--Scientists Recreate Ancient Mating Call from Dinosaur Age

（单词翻译）

Scientists Recreate Ancient Mating Call from Dinosaur¹ Age

It was probably a noisy world, with thousands of other animal sounds, rushing streams and the rustle² of giant ferns and coniferous trees.
Fernando Montealegre studies how insects sing and hear.
When he and his colleagues at the University of Bristol got their first look at a fossilized pair of katydid wings found in China, it was obvious that bug³ was a music maker⁴.
Montealegre says Achaboilus musicus, as the new species was named, already displayed features that modern-day katydids use to make sound.
“One wing in extant species has a file vein⁵, modified with a series of pegs⁶ and the other wing has a scraper. So they open and close the wing and during the closing cycle they produce the sound. The scraper hits the file teeth and generates vibrations⁷.”
Montealegre and colleagues compared the pegs on the vein on the 7-centimeter-long katydid wings’ with those of 59 living bush cricket or katydid species. Unlike insects today that have varied⁸ rhythm and call patterns, Montealegre determined⁹ that A. musicus had a simple, single-frequency pulsing tone.
“It’s a primitive¹⁰ condition, just continuous singing. And in this case, the continuity would be a chirp¹¹ every one second.”
The male’s low six-kilohertz tone was especially adapted to carry over long distances at night.
The mating call rose from the forest floor and captivated females, despite other Jurassic distractions¹². Montealegre says that sound marked a new era in acoustic¹³ evolution.
“Many animals developed these acoustic capabilities¹⁴. And it was a noisy environment and so they needed to produce private channels that they would attain¹⁵ with pure tones and tuning¹⁶ the sender and the receiver at the same respective frequencies for each animal.”
But any predator¹⁷ that could have picked up the sound would have been a problem. Mammals may have fed on them. It wasn’t until 100 million years later that bats appeared. By that time katydids had developed ultrasonic¹⁸ mating calls that their enemies could not hear.
The work is reported this week in the Proceedings¹⁹ of the National Academy of Sciences.