Posts tagged Duke University
CU Boulder study: fossils show evolution of bug hearing
Jan 3rd
FROM COLORADO HINT AT ORIGIN OF INSECT HEARING
How did insects get their hearing? A new study of 50-million-year-old cricket and katydid fossils sporting some of the best preserved fossil insect ears described to date are helping to trace the evolution of the insect ear, says a new study involving the University of Colorado Boulder and the University of Illinois at Chicago.
According to University of Colorado Museum of Natural History paleontologist Dena Smith and University of Illinois Professor Roy Plotnick, who collaborated on the new study at the National Evolutionary Synthesis Center, or NESCent, in Durham, N.C., insects hear with help from some very unusual ears.
Grasshoppers have ears on their abdomens. Lacewings have ears on their wings. The ears of the tachinid fly are tucked under the chin. “Insects have ears on pretty much every part of their body except on their head proper,” Plotnick said.
Insects have evolved ears at least 17 times in different lineages, said Smith, also an assistant professor in CU-Boulder’s geological sciences department. Smith and Plotnick are trying to figure out when different insects got their ears, and whether predators may have played a role.
Modern insects use their ears to tune in to each other’s chirps, trills and peeps. Think of the chorus of crickets, or the love songs of cicadas. But many species can also pick up sounds beyond the range of human hearing, such as the high-pitched sonar of night-hunting bats, according to Smith and Plotnick.
Crickets, moths and other flying insects have ultrasound-sensitive hearing and can hear bats coming, diving or swerving in midflight to avoid being eaten. Insects that evolved such supersensitive hearing would have had a crucial survival advantage, the researchers said.
“The big evolutionary trigger for the appearance of hearing in many insects is thought to be the appearance of bats,” Plotnick said. “Prior to the evolution of bats we would expect to find ears in relatively few insects, but after that we should see ears in more insect groups,” he explained.
Did insect ears get an upgrade when bats came to be? Before this study the fossil evidence for insect hearing was too poorly preserved or scantily described to know for sure, according to the researchers.
To find out, Plotnick and Smith turned to remarkably well-preserved fossils from a series of lake deposits in Wyoming, Utah and Colorado known as the Green River Formation, where some of the earliest bats are found.
Roughly 50 million years ago, fine-grained sediment covered and buried the animals that lived there and managed to preserve them in exquisite detail. “You can see every tiny feature down to the veins in their wings and the hairs on their legs,” said Smith, who has been studying Green River fossils for more than 15 years.
For this study, the researchers examined fossils from a Green River site in Colorado, focusing on crickets and katydids, which have ears on their front legs, just below their knees.
The team scoured more than 500 museum drawers of Green River fossils for crickets and katydids with intact front legs, looking for evidence of ears. “You can just make them out with the naked eye,” Plotnick said. “They look like the eye of a needle.”
In crickets and katydids living today, the ear is a tiny oval cavity with a thin membrane stretched over it that vibrates in response to sound, much like our own eardrum.
The fossil ears measured half a millimeter in length, and were virtually identical in size, shape and position to their modern counterparts. The findings suggest that this group of insects evolved their supersensitive ultrasonic hearing long before bat predators came to be, the researchers say. “Their bat-detecting abilities may have simply become apparent later,” Smith said. “The next step is to look for ears in other insect groups.”
The study appears in this month’s issue of the Journal of Paleontology. NESCent is a nonprofit science center dedicated to cross-disciplinary research in evolution and is jointly operated by Duke University, the University of North Carolina at Chapel Hill and North Carolina State University, with funding from the National Science Foundation.
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CU-BOULDER PART OF INTERNATIONAL TEAM TO DISCOVER NEUTRINOS CAN CHANGE ‘FLAVORS’
Jun 15th
An international research team led by Japan and including the University of Colorado Boulder may have taken a significant step in discovering why matter trumped antimatter at the time of the Big Bang, helping to create virtually all of the galaxies and stars in the universe.
The experiment, known as the Tokai to Kamioka experiment, or T2K, included shooting a beam of neutrinos underground from the Japan Proton Accelerator Research Complex, or J-PARC, on the country’s east coast to a detector near Japan’s west coast, a distance of about 185 miles. Elementary particles that are fundamental building blocks of nature, neutrinos generally travel at the speed of light and can pass through ordinary matter, like Earth’s crust, with ease. Neutrinos come in three types: muon, electron and tau.
The T2K team discovered that muon neutrinos can spontaneously change their “flavor” to electron neutrinos, a finding that may help explain why the universe is made up mostly of matter rather than antimatter, said CU-Boulder Assistant Professor Alysia Marino of the physics department, who is part of a university contingent that participated in the experiment. Scientists had previously measured the change of muon neutrinos to tau neutrinos and electron neutrinos to muon neutrinos or tau neutrinos, she said.
The shift of muon neutrinos to electron neutrinos detected in the new experiment is a new type of neutron oscillation that opens the way for new studies of a matter-antimatter symmetry called charge-parity, or CP violation, said Marino. “This CP violation phenomenon has not yet been observed in a neutrino, but may be the reason that our universe today is made up mostly of matter and not antimatter,” she said.
Scientists believe matter and antimatter were present in nearly equal proportions at the onset of the Big Bang. Since matter and antimatter particles cancel each other out, it has been proposed that there must have been CP violation in the early universe that produced slightly more matter than antimatter, which accounts for all the stars, galaxies, planets and life present today.
The T2K project is a collaboration of roughly 500 scientists from 12 nations. Other participating U.S. institutions include Boston University, Brookhaven National Laboratory, the University of California-Irvine, Colorado State University, Duke University, Louisiana State University, Stony Brook University, the University of Pittsburgh, the University of Rochester and the University of Washington. The United States contingent is funded by the U.S. Department of Energy.
The CU-Boulder group includes Marino, physics Associate Professor Eric D. Zimmerman, postdoctoral researchers Stephen Coleman and Robert Johnson, graduate students Andrew Missert and Tianlu Yuan, and former undergraduates Christopher Vanek, Bryan Kaufman, Eric Hansen, Zhon Butcher and Joshua Spitz.
The CU-Boulder team designed and built one of three magnetic horns used to generate neutrino beams. The horns are large aluminum conductors that use very high electrical currents to produce a magnetic field. The magnetic field focuses on short-lived neutrino-producing particles called pions and kaons, enhancing the intensity of the neutrino beam, said Zimmerman.
The CU-Boulder researchers also developed a device to monitor the position of the proton beam that creates the neutrinos. In addition, they contributed to the installation and operation of a T2K detector at the J-PARC site 60 miles northeast of Tokyo that measures the neutrinos right after they are produced, Marino said.
Zimmerman said more data will be required to confirm the new results. The J-PARC accelerator is being repaired following damage from the earthquake that hit Japan on March 11. The accelerator and experiment are expected to be operational again by the end of the year, said Zimmerman.