The bladderwort: No ruthless microbe killer A carnivorous water plant with tiny

traplike bladders dotting its leaves may not deserve its reputation as a relentless predator, says a Florida scientist.

A survey of bladderwort plants in the Everglades found far more bladders har- boring living organisms than dead ones, re- ports Jennifer H. Richards of Florida Inter- national university in Miami. Although the plant does kill insect larvae, it offers a safe home for smaller organisms, which may pay rent in nutrients. The bladderwort, or Uhicularia purpurea, “is not like a bear trap,” she says, but more like a terrarium.

A mature bladder has a built-in trap door that operates on a hair trigger. When the plant pumps some water out of the bladder, the door can snap inward if an insect larva or even a bit of debris brush- es it. The ensuing inward rush of water draws anything nearby into the bladder. A few keen-hearing naturalists have re- ported tiny pops from door openings.

Earlier work in other laboratories had shown that the bladders absorb nutri- ents from their catch. To study feeding in the wild, Richards monitored and sam- pled plants from several Everglades loca- tions. The species ranges from the t rop ics to Canada.

With a microscope, Richards catego- rized contents of about 1,400 pinhead- size bladders. Immature bladders were

empty, but virtually all the mature ones held photosynthetic microbes, such as algae. Microscopic animals called rotifers showed up in 20 percent of the bladders. All the tiny occupants seemed alive and well, Richards reports in the January AMEFUCAN JOURNAL OF BOTANY.

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Floating in water, bladderworts grow filaments that support tiny bladders (lower arrow), about 370 bladders per whorl. Flower stems reach above the water to bloom (upper arrow).

In contrast, the insect larvae and other larger creatures found in 6 percent of the bladders were dead. Richards says that although the bladders do absorb nutri- ents from prey, it’s unlikely that the rare prey could repay more than a whisker of the resources that the plant invests in its bladders. On average, the plants dedi- cate about a quarter of their biomass to

Conductors single out sour side notes Experienced classical-music conduc-

tors wield their batons like master an- glers, pulling musical keepers out of an orchestra’s pool of instrumentalists. This impressive feat-which occurs on- ly after many practice sessions leading up to a concert-requires maestros to monitor both the orchestra’s overall performance and the contributions of specific violinists, oboists, trumpeters, and so on.

Skilled conductors sort through the symphonic cacophony by homing in on subtle changes in sounds originating from precise locations to the side as well as in front of them, a new study finds. Measurements of the brain’s elec- trical activity indicate that conductors allocate just as much attention to pe- ripheral sounds as to centrally located sounds, a team of neuropsychologists reports in the Feb. 1 NATURE.

Neither nonmusicians nor classical pianists possess this acoustic side-scan- ning ability, underscoring its key role in orchestra conducting, say Thomas F. Munte of the University of Magdeburg in Germany and his colleagues.

“Our findings provide [an] example of how extensive training can shape cogni- tive processes and their neural under-

FEBRUARY 3,2001

pinnings,” the scientists conclude. Munte’s team studied three groups:

classical-music conductors who had an average of 19 years of conducting experience, classical pianists who had played professionally for an average of 16 years, and people who had no musi- cal training of any kind. Each group con- sisted of six men and one woman.

Each participant sat in a chair facing a set of three loudspeakers. Another set of three speakers stood on the person’s far right. Both arrays of speakers simultane- ously delivered bursts of electronic noise that fell within a narrow range of acoustic frequencies. At random times, a single central or peripheral speaker emitted a burst outside of the usual frequency range.

All three groups showed about the same accuracy in noting the deviant sounds from the central speakers. How- ever, conductors made markedly fewer errors than the other groups in identify- ing the deviant peripheral sounds, the researchers say.

Electrical activity in the conductors’ brains-measured by electrodes placed on the scalp during testing-exhibited a pattern associated with heightened at- tention when they heard either central

SCIENCE NEWS, VOL. 159

bladders, Richards calculates. The bladder tenants might offer the

plant valuable carbon dioxide, Richards speculates. In other aquatic plants, she says, a shortage of carbon dioxide limits growth. She speculates that the bladders’ microinhabitants collectively boost the plant’s supply. She suspects that minia- ture ecosystems inside the bladders also yield other nutrients the plant can absorb.

Robert Ulanowicz of the Chesapeake Biological Laboratory in Solomons, Md., has made computer models of bladder- wort growth. He questions Richards’ idea of a mutualism between the plant and its bladder dwellers. “It remains unclear how the captured organisms would benefit,” he says.

The new paper reminds Thomas Miller of Florida State University in Tallahassee of his own work on Sarracenia purpurea, a carnivorous plant with pitcher-shaped leaves. Despite their reputation as omniv- orous death traps, these plants don’t se- crete any flesh-eating enzymes within their traps, Miller notes. In fact, several insect larvae survive only inside the pitchers. The plant, in turn, absorbs nu- trients shed by the larvae.

Richards now chuckles that she herself once sensationalized the lifestyle of Uhic- ularia, the genus that includes 42 percent of the world’s carnivorous plants. “I was a believer,” she deadpans, recalling her ear- ly plan to analyze the bloodthirsty preda- tor. “Then, I studied it.” 4. Milius

or peripheral sound deviations. The other two groups showed attention-re- lated brain activity only when they heard deviant central sounds.

Conductors who had as little as 6 years of experience on the podium lo- cated deviant peripheral sounds as well as their colleagues who had brandished their batons for nearly 30 years, Munte notes. “I suspect that conductors ac- quire the ability to localize peripheral sounds within the first few years of pro- fessional experience,” he says.

Robert J. Zatorre, a neuroscientist at Montreal Neurological Hospital who studies music perception, is intrigued by the new results. “Conductors are re- sponsible for fine-tuning the way in which each member of an orchestra plays a musical composition,” Zatorre holds. “The ability to identify the source of peripheral sounds is crucial for conductors.”

Music schools typically attempt to teach aspiring conductors to pinpoint errors by having musicians intention- ally play a wrong note from various sec- tions of the orchestra, Zatorre adds. Fledgling conductors who are initially able to identify the source of peripheral sounds with at least fair accuracy may benefit the most from further experi- ence, he suggests. -B. Bower

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