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Published: Monday, 10/6/2003

Grasshopper hears on its stomach

You might say the bladder grasshopper is all ears.

You also might say it helps explain how complex organs like ears and eyes evolved in tiny steps from earlier, unrelated structures.

Moira Van Staaden, a professor at Bowling Green State University, was studying the southern African bladder grasshopper with the Latin name of Bullacris membracioides. It's an impressive animal. Although a mere two inches long, its calls are nearly as noisy as a jackhammer, and audible more than a mile away.

It's also primitive. Genetic studies show it emerged during the Jurassic period, which began 206 million years ago.

Oddly enough, this grasshopper seemed to have no ears. Most insects use a membrane called a tympanum to translate sound waves into nerve impulses. The bladder grasshopper is tympanum-free.

Instead, Dr. Van Staaden was surprised to discover the animal has six pairs of unusual hearing organs along its abdomen. She published her findings this month in The Journal of Comparative Neurology.

These “ears” are actually slightly modified versions of something called a stretch receptor, a tiny organ that normally monitors the movement of body parts in relation to one another.

“People who have a problem with evolution think you cannot get a complex organ from simple precursors,'' Dr. Van Staaden said. This is an example of how such changes occur.

Crayfish, it turns out, can teach one of life's important lessons: Pick your fights.

Paul A. Moore, a researcher from Bowling Green State University, decided to watch two species of crayfish in their native habitats. So for the last seven years, he's grabbed his scuba gear and watched the crayfish action on the bottom of Douglas and Burt lakes near the tip of the Michigan mitten.

Dr. Moore wanted to compare lake-bottom behavior to what he sees in his laboratory, where crayfish engage in ferocious battles that last 10 to 15 minutes.

It turns out, wild crayfish are neither so dogged nor so violent. In the lake, their battles ended in seconds, and seldom involved more than muscle flexing.

Fights turn more violent, moving to boxing, and finally to grabbing, only when the crustaceans fought over something of great value, Dr. Moore reported in a recent issue of the Biological Bulletin. In the wild, fights for shelter can last as long as 15 seconds. Fights for readily available food are over in two seconds.

All this was good news for lab crayfish. Redesigned crayfish tanks now include hiding places. This way, animals can pick their fights the way they do in the wild.

If you're foolhardy enough to talk on the phone while you drive, you're also less likely to wear a seatbelt, two new studies of Michigan drivers reveal.

David W. Eby, a senior associate research scientist at the University of Michigan, conducted two studies that found seatbelt use lower among cell phone talkers. One study of 12,000 drivers observed at a variety of intersections showed that 76 percent of cell phone users buckled up, while 83 percent of non-talkers were wearing seatbelts. The results are published in the current issue of Accident Analysis & Prevention.

A second study of 23,000 drivers, soon to appear in the journal Transportation Research Record, found that while 81 percent of the phone-free drivers buckled up, only 70 percent of cell phone users did.

The study only covered people using handheld cell phones, Dr. Eby said, since it's difficult to determine in a curbside inspection which drivers are using hands-free phones, and which are talking to themselves, or singing along with the radio.

“Unsafe driving behaviors, risky driving behaviors, occur in constellations. If a person does one thing that's unsafe, they're likely to do a bunch of things that are unsafe,'' Dr. Eby said.



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