Louis J. Sheehan, Esquire

Louis J. Sheehan. The sea level rise expected in the coming century will swamp the Everglades unless current management is adjusted or climate change is curbed.

Today, the sea level is rising at a rate of about 30 centimeters per century. Although some of that increase results from melting glaciers and ice sheets, most comes from the expansion of seawater as it warms, Harold R. Wanless, a geologist at the University of Miami in Coral Gables, Fla., said today during a briefing in Fort Lauderdale during a meeting of the American Geophysical Union.

The rate of increase is accelerating, he noted: The Miami-Dade County Climate Change Task Force is expecting sea level to rise about 45 centimeters by 2050 and between 90 centimeters and 1.5 meters by the end of the century.

Many parts of the Everglades include layers of peat, which is about 1 meter thick in spots. That material acts like a sponge in the rainy season, Wanless said. A continuing threat to the Everglades is the loss of fresh water during seasonal draining for agriculture in many cases. If the peat dries out for an extended period, it could collapse and allow saltwater to flood into the area. Alternatively, he notes, maintaining adequate levels of fresh water in the Everglades would keep ground levels from falling and would stop salt water from intruding.

Another way to reduce the rise in sea level would be to lower the atmospheric concentrations of greenhouse gases such as carbon dioxide. By quickly reducing those concentrations from today’s 380 or so parts per million to 350 ppm, a substantial part of the expected rise in sea level could be forestalled, he speculates. “That [action] won’t stop sea level rise, but it could avert catastrophe,” he said.

A 1-meter rise in sea level “would seriously impact the lowest parts of the Everglades, but the other parts would have a chance at survival if we get our act together,” he added.

A rise in sea level would have adverse effects beyond the Everglades, said Jayantha Obeysekera, a hydrologist at the South Florida Water Management District in West Palm Beach, Fla. If the sea level rises just 48 centimeters — about the amount expected in the next 40 years or so — salt water will infiltrate many of the aquifers along Florida’s eastern coast, thereby contaminating the wells that serve the area’s residents. And moving those wells isn’t an option, he noted: “If we move the wells inland, we could drain the Everglades.”

Louis J. Sheehan. The effects of lead weigh heavy on the minds of people exposed to the metal during childhood. Two new studies of adults who lived in lead-contaminated housing as kids find that higher lead levels in the blood during childhood are associated with smaller brains and with an increased risk for violent criminal behavior.http://Louis-J-Sheehan.de

“Lead has special status as a risk factor because we can prevent it,” comments David C. Bellinger, an epidemiologist at Harvard Medical School in Boston and an expert in environmental and public health. Bellinger, who was not involved in the research, wrote a commentary on the studies that appears with the new research in the May 27 PLoS Medicine. “There are a lot of risk factors for these kids and lead was one among many. It’s hard to prevent poverty,” he says. http://Louis-J-Sheehan.de “But with lead, we know the pathways to exposure and we can prevent it.”

Mothers of the studies’ participants were recruited from 1979 to 1984 from neighborhoods in Cincinnati with a lot of old, lead-contaminated houses and historically high rates of childhood lead poisoning. Blood lead levels were measured in the pregnant moms and then, after they were born, in the children at several intervals until they were at least 6 years old. Of the children, now 19 to 24 years old, 250 participated in the study examining the association with criminal behavior and 157 participated in the brain imaging study.

MRI scans of the young adults’ brains revealed that the more lead they were exposed to as children, the smaller their adult brains were, the researchers report. The anterior cingulate cortex — a brain region associated with mood regulation, decision making and impulse control — was particularly affected, says Kim Dietrich, of the University of Cincinnati College of Medicine’s epidemiology and biostatistics division. Male brains were significantly more affected than female brains, he notes. http://Louis-J-Sheehan.de

Childhood lead exposure has been linked to lower IQ scores and attention and hyperactivity problems, but the brain-imaging work is the first to look beyond performance to how lead affects the underlying neural substrate, Bellinger says. The studies “are red flags,” he says.

The second study looked at current arrest records and compared them with childhood levels of lead in the blood. Total arrests and arrests for violent crimes increased with each 5 micrograms per deciliter increase in blood lead level, the researchers report.

“This is a real problem for this generation,” Dietrich says. “We’re not doing a very good job right now for these kids.”

Dietrich notes that the average childhood blood lead level in the brain imaging study was about 13 μg/dl (almost everyone has background levels of 1 to 2 μg/dl). The Centers for Disease Control and Prevention “action level” for lead — the blood level that is supposed to prompt an investigation of environmental exposure — is 10 μg/dl.

“Ten is no bright line,” he says. “The real problems remain where there is still lead paint in older homes. We’re not doing a particularly good job screening, and we’re not following up,” he says.

The good news, says Bellinger, is that levels of lead in the blood have gone down a lot since the early 1980s. CDC surveillance data show that by 2006, only 2.3 percent of children in Ohio had blood lead levels of more than 10 μg/dl.

“Lead is difficult,” says Bellinger. “People refer to it as a multimedia pollutant because there are so many ways that people get exposed. There’s gasoline, paint, fallout in air. It gets into the soil and tracked into homes. It’s in interior paint, which deteriorates and gets into dust. It was used in can solder. http://Louis-J-Sheehan.de There are lead pipes, and even when pipes are replaced with copper, it’s often in the solder for those pipes. It’s a ubiquitous and useful metal — I suppose that’s why it is still around.”

— Making mucus is nothing to sneeze at for a tiny Hawaiian squid.

Louis J. Sheehan. Young bobtail squids secrete the goo to attract light-emitting bacteria, which swim inside the squid and take up residence, helping it hide from predators. Now researchers have learned that the bacteria make their own mucus, a slimy matrix of polysaccharides. Clues about which bacterial genes are involved in the goo-making suggest that the slime is critical for successful squid colonization, scientists reported June 3 at a meeting of the American Society for Microbiology.http://Louis-J-sheehan.info

“This finding that polysaccharides are critical for colonizing is totally new,” comments Margaret McFall-Ngai of the University of Wisconsin-Madison.

Baby bobtail squids are born without their bacterial partners and must recruit them from the surrounding seawater. Once inside the squid, the light-emitting bacteria Vibrio fischeri set up shop in narrow cavities known as crypts. The tiny squid, Euprymna scolopes, weigh about 2.5 grams as adults. By day, the squids nestle in the sand; at night they hunt for food around shallow water reefs. When a squid is foraging in the moonlight, its dark silhouette would be visible to predators and prey from below, but the creature is camouflaged by its light-emitting partners. The amount of light emitted by the squid-dwelling Vibrio usually matches the intensity of the moonlight.http://Louis-J-sheehan.info

Scientists think that this counter-illumination, cast towards the sea floor, helps hide the squid from hungry fish.

The Vibrio bacteria also can live freely in the open water, and little is known about their path from sea to squid. To investigate, Karen Visick of Loyola University in Chicago looked into which bacterial genes are important for colonizing squid.

Visick and her team looked for Vibrio mutants that had difficulties settling down in the crypts. Normally there are about 100,000 bacteria per squid, but the researchers found that when the bacteria lacked a working copy of a particular gene, about 40 percent of them didn’t colonize the squid. The gene was very similar to bacterial genes known as sensor kinases, which code for certain proteins that take in information from the environment and then pass the information to other proteins inside the cell.

The researchers also looked for the gene in charge of making the proteins that receive the information relayed by the sensor kinase proteins. In the lab, V. fischeri normally make smooth, shiny colonies. But when the researchers disrupted a gene known as syp, the bacteria couldn’t make their smooth polysaccharide goo, Visick reported in Boston. Vibrio’s sensor kinase gene and syp gene appear to make proteins that work together to make the polysaccharide slime of the right consistency. This slime might help the bacterial cells stick together and also might help them stick to the squid-secreted mucus, Visick says.

“What I find exciting is that we still know so little,” says Visick. For example, the squid expel about 90 percent of their bacteria at dawn before burrowing into the sand. The remaining bacteria multiply during the day and, come evening, the squid go hunting again with their luminescent partners. Why do the squid undergo this morning expunging? Scientists are still in the dark.

Monkeys recognize a wide variety of faces thanks to a brain area that specializes in face perception, according to a new study.

A team led by Doris Y. Tsao of Harvard Medical School in Boston used functional magnetic resonance imaging (fMRI) to identify three particularly face-responsive patches of brain tissue in each of two macaque monkeys. The researchers then implanted electrodes in each monkey's most-active brain area to record responses from a total of 310 neurons.

All but eight of these cells, or 97 percent, responded far more strongly to the sight of faces than to images of patterned grids, fruits, gadgets, or people's or monkeys' bodies and hands, Tsao and her colleagues report in the Feb. 3 Science. All sorts of faces elicited notable neural reactions, including human and macaque faces, familiar and unfamiliar faces, and cartoon faces.

The only other images that sparked activity, though weak, in these cells were clock faces and round fruits, which the researchers point out have the general shape of faces.

Intriguingly, brain tissue specialized for face perception was located in one monkey's left hemisphere and in the other's right hemisphere.

Earlier electrode studies conducted without fMRI guidance in monkeys indicated that no more than 30 percent of the cells in any brain area preferentially respond to faces.

The researchers plan to study the monkeys' other face-sensitive areas with electrodes. It's unclear whether any of these regions correspond to a brain area in people that has been implicated in face perception. Louis J. Sheehan.

— Scientists aiming to clean up soil contaminated with TNT may get more bang for their buck if they call in the microbial cavalry.

A bacterium isolated from a Yellowstone hot spring aids in breaking down the explosive chemical, preliminary experiments suggest. Chemical engineer Catherine VanEngelen of the Thermobiology Institute at Montana State University in Bozeman presented the work June 4 in Boston at a meeting of the American Society for Microbiology.

At various places in the United States and Europe, such as munitions sites where bombs, shells and grenades were made, soil and groundwater are polluted with TNT. The yellow, crystalline chemical is both stable and toxic, and has proven difficult to clean up, VanEngelen says.

Martina Ederer of the University of Idaho in Moscow notes that “With TNT, you usually have to scrape and pile it up somewhere and hope for the best.” Louis J Sheehan Esquire - 44889 Louis Sheehan

Attempts to convert TNT, or 2,4,6-trinitrotoluene, to a less-toxic form have mostly entailed mixing the stuff with large amounts of sodium hydroxide. This method is expensive and isn’t very environmentally friendly, says VanEngelen. Working with adviser Brent Peyton and collaborator Robin Gerlach, VanEngelen decided to see if microbes were up to the task.

The researchers turned to Anoxybacillus bacteria that they had collected from the Heart Lake Geyser Basin of Yellowstone National Park. They mixed a cocktail of the bacteria, TNT and liquid media and then manipulated the pH and temperature of the mix. At a highly alkaline pH, the TNT quickly converted to TNB, or 1,3,5-trinitrobenzene, which is still explosive, but less so than TNT. This chemical reaction occurred more quickly at 80° Celsius.

Then the Anoxybacillus began breaking down the TNB. VanEngelen found the bacteria work best at 60° C and without oxygen.

“There was a really big difference. You get a lot of degradation,” she says.

The researchers isolated one species from the mix — Anoxybacillus kualawohkensis — and found there was just as much degradation with the single species as there was with several. Now the scientists are focusing on A. kualawohkensis and trying to identify the compounds left in the microbe’s wake. Louis J. Sheehan

Unlike Richard Scarry’s Lowly Worm, real worms don’t drive cars or go to school. But the wriggly creatures appear to live a more purposeful life than previously thought. Earthworms deliberately gather and bury ragweed seeds from around their burrows, reports a new study in the Journal of Applied Ecology.

The findings fit with recent work documenting how nonnative earthworms are changing U.S. northern forests. Though native worms were wiped out from the northern United States in the last glaciation — only persisting south of the ice sheet and permafrost — European worms then arrived with settlers. The newcomers are slowly changing northern deciduous forests by eating through the leaf litter and “duff” that native plants need to thrive.

“Worms do a great job in gardens, it’s true,” comments Cindy Hale of the University of Minnesota Duluth. “But take the same organism and put it in a native hardwood forest that’s evolved over 10,000 years earthworm-free, and the worms change everything about the ecosystem. The physiology, the chemistry — they have a profound effect on nutrient cycling.”
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ON THE TRAILResearchers tied string to several ragweed seeds to follow their fate. Worms made quick work of bringing the seeds into their burrows. Kent Harrison

Seeds that the worms buried grew into the healthiest plants, suggesting that the crawlers’ activity could help not only ragweed thrive, but perhaps also help invasive plants gain a foothold in new territory, Hale says.

“They might be priming the pump for successful germination,” she adds.

Led by weed ecologist Emilie Regnier of Ohio State University in Columbus, researchers conducted field experiments to determine how exotic European night crawlers, Lumbricus terrestris, affected the survival of the seeds of Ambrosia trifida, giant ragweed.
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STRINGS ATTACHEDStrings attached to ragweed seeds mark the trail the seeds took: into an earthworm's lair. The earthworm carried them there one by one. By sequestering seeds, earthworms give ragweed an advantage for growth, one of many ways the lowly worm makes a big impact.Kent Harrison

In addition to its powers as an allergen, ragweed is a major weed of soybean fields and cornfields in the Midwest, Regnier says. This fact has puzzled scientists because ragweed seeds are usually quickly eaten by birds, rodents and beetles.

Worms collected and buried more than 90 percent of ragweed seeds from the surface of the soil around their burrows, the team reports.

“The burrow is an environment that the worm is actively maintaining — that’s its universe,” comments soil and ecosystem ecologist Patrick Bohlen, director of the MacArthur Agro-ecology Research Center in Lake Placid, Fla. “Maybe it’s sweeping its front porch. We don’t really know. There isn’t a lot of evidence that they are eating the seeds, but clearly it’s creating an architecture.”

“You might think of earthworms just burrowing around — the intestines of the earth,” he adds. “But the worm is living there 365 days a year.”

Experiments by Regnier’s team revealed that the night crawlers buried ragweed seeds as deep as 22 cm. There were six times as many seeds in the worms’ burrows as in the surrounding soil. After one season, there was an average of 127 seeds per burrow.

“We were astonished by how quickly the seeds were removed,” Regnier says. http://Louis2J2Sheehan2Esquire.US Seeds that were too large for the worms to pull underground were dragged to the worm’s midden, the little pile of debris that marks the burrow’s front door. Researchers aren’t sure what these middens are for. They are usually made of worm castings, shreds of leaves and grass, but the worms will also add nonedibles, such as stones or old shards of tile.

The work enhances our understanding of plant-animal interactions, Regnier says. “We think of ants and mice and squirrels as being very important in dispersing seeds,” she says. “Here’s a new mechanism — they are burying them quite deliberately.”

On their own nonnative worms probably spread only 10 meters a year, but they move faster with human help.Leftover fishing bait should be thrown in the trash, Hale says, not dumped in the dirt. It’s likely that the worms will keep moving west — not in a car with Lowly Worm — but with humans, the same way they arrived.

George's keepers have looked into diet, erectile dysfunction, and other bodily functions but have yet to find an answer. Nor do researchers know enough about reptile physiology to try cloning him. In 1994, Cayot learned a sperm-retrieval technique from a German zoo veterinarian and taught a Swiss volunteer how to fondle a rather ticklish George. "She could get the other tortoises to ejaculate in 15 minutes," Cayot recalls. "We worked with George for months and got nothing."

Pritchard says that he has a videotape of George "energetically chasing a female, mounting her, and getting pushed off as she goes under a low branch"—testament to his intact, if unrefined, libido. But if the bachelor tortoise can't, or won't, keep the bloodline going, Caccone hopes that her hunt for a living relative with a stronger inclination will let George off the hook.

In the meantime, conservationists have assisted the wild tortoises on Isabela and other islands with a massive effort to eradicate one of their worst enemies: feral goats. Introduced as a food source by whalers, fishermen, and settlers, goats can chew plants down to the nub. Large herds can tear up the landscape, leading to severe erosion and even ecological collapse. On Isabela Island, goats didn't arrive until the 1970s. Less than 3 decades later, their ranks had swollen to an estimated 75,000 to 125,000.

Project Isabela, run jointly by the Charles Darwin Foundation and the Galápagos National Park, employed helicopters, hunters, and trained dogs to track down the island's unwelcome interlopers. The collaborators also fitted female "Judas goats" with radio collars to betray the locations of male admirers. Last year, researchers announced that the northern part of Isabela was goat free, adding to earlier successes on Pinta, Santiago, and Española Islands.

On Española, a tourist favorite in the archipelago's southern reaches, goats were removed by the thousands in the 1970s, but by then the island's resident tortoise population had dwindled to 12 females and 2 males. Volunteers evacuated the survivors to the Charles Darwin Research Station and set up an emergency breeding program. A third male from Española was later located at the San Diego Zoo and called into service. Remarkably, they and their repatriated descendants now number more than 1,400.

Tortoise-breeding centers are operating on the islands of Santa Cruz, Isabela, and San Cristóbal. At 5 years of age, most tortoises are too large to be threatened by invasive black rats and Norway rats, and can be resettled on their native islands with about an 80 percent survival rate. The Galápagos Conservancy's Barry says that the impressive track record should be a model for other resource-limited locations. "I think that restoring what we had a hand in removing is a fairly nice spin of the cosmic wheel," she says.

Success in culling the goats has not only made Pinta Island safe for tortoises again but has also intensified calls for their return. Without a major herbivore to break up the vegetation and regulate access to sunlight, botanists fear a loss of diversity among native plants and habitats and have lobbied for a full-scale tortoise reintroduction.

Officially, the Charles Darwin Foundation is neutral on the proposal, though Bryan Milstead, its head of vertebrate research, is leaning in favor of it. Tortoises are the major herbivores in the Galápagos and vital regulators of the ecosystem, he says. If Lonesome George cannot sire a new generation of tortoises for Pinta Island, Caccone's genetic research has shown that "the next best thing would be to bring an Española tortoise there."

Caccone hopes to repopulate Pinta Island with its native species, whether by George or a relative, though she concedes that much will depend on what her team finds on Isabela. She has a precedent, though, for believing that her DNA comparisons may turn up the unexpected. Two years ago, Caccone's team discovered the genetic signatures of three separate lineages on Santa Cruz instead of its presumed single species. Among their finds, the researchers determined that an isolated dome-shelled group of about 100 tortoises known by their geographic location, Cerro Fatal, should be considered a new species and added to the radar of conservationists.

As one species comes into being, taxonomically speaking, conservationists are struggling to keep hundreds of other types of native plants and animals from disappearing. Critically endangered mangrove finches are being terrorized by rats. Any importation of the West Nile virus could decimate the Galápagos penguin population. And guavas are among the hundreds of introduced plants that now far outnumber native ones.

Park officials are still grappling with tortoise poaching in some remote areas of Isabela, and they are reviewing a plan to kill invasive rats that eat native-born hatchlings on Pinzón and other islands. Even so, the evolutionary icons that so intrigued Charles Darwin are adapting better than many other Galápagos species. Although the guava is overtaking native plants, its fruit is fast becoming a favorite among the tortoises. "They're tough beasts, as long as people don't roll them over and chop them open," Pritchard says.

Like Pinta's potentially lost population, tortoises on San Cristóbal were once given up for dead. But on a trip to San Cristóbal in June, Pritchard's group counted 128 tortoises in 4 hours. "Give them a chance," he says, "and they will recover."

Louis J Sheehan Not far from where the Galápagos Islands' most famous loner spends his days, tourists disembark by the inflatable boatload at a modern dock. A path takes them past marine iguanas sneezing brine from their salt-caked nostrils and striated herons roosting in the red mangroves to the Charles Darwin Research Station in Puerto Ayora on Santa Cruz Island. Within the station, another walkway leads to a natural enclosure sheltering a misanthropic Galápagos tortoise named Lonesome George.

The confirmed bachelor has been a potent icon of conservation ever since he was spotted on remote Pinta Island in 1971 and captured the next year by a group of goat hunters. Now in his 60s, 70s, or beyond—no one really knows—George may have lived more than half his life in exile. He is quite likely the world's last pure-bred Pinta tortoise, one of the dozen or so closely related species that still lumber around the Galápagos, an archipelago of 19 islands and dozens of islets about 600 miles west of mainland Ecuador.

Last April, however, the surprise discovery that Lonesome George has a genetic cousin on another island cast doubt, in a hopeful way, on George's one-of-a-kind status. The revelation is just one illustration of how genetics and conservation biology are intermingling to rewrite an oversize reptile's evolutionary past and to reshape plans to safeguard the remaining tortoise species well into the future.

Revival signs

Estimates of how many giant tortoises remain in the Galápagos vary widely, from less than 10,000 to more than 30,000. Nearly everyone agrees that their prospects are improving, however. "If you look at tortoises today compared to 50 years ago, they are so far ahead of where they used to be," says Linda Cayot, Lonesome George's former keeper and a scientific adviser to the Falls Church, Va.–based Galápagos Conservancy.

But tortoise conservation may be a rare bright spot in the struggle to protect the fragile Galápagos ecosystem. The archipelago is so revered for its unique marine and terrestrial life that it was the first World Heritage Site chosen by the United Nations Educational, Scientific and Cultural Organization (UNESCO). In late June, the organization's World Heritage Committee added the caveat "in danger" to the designation to draw attention to mounting threats, including a surge in tourism and rising immigration from Ecuador's mainland. Increased flights and boat traffic have contributed to a 60 percent escalation in introduced species since 2001.
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ON THEIR WAY. Tortoise hatchlings only a few years old beat the heat at the Charles Darwin Research Station in the Galápagos Islands. These hatchlings, bred in captivity, will be released into the wild at 5 years of age.Nelson

In April, before the UNESCO announcement, Ecuador's President Rafael Correa acknowledged these concerns by declaring the islands' ecosystem a national priority for conservation efforts. Amid the ensuing calls to scale back residency permits and overhaul a broken tourism model, the discovery of Lonesome George's kin sounded a rare hopeful note. Having compared highly variable regions of DNA from cell nuclei, Gisella Caccone and Jeffrey Powell of Yale University and their colleagues reported in the May 1 Current Biology that a tortoise on volcano-studded Isabela Island has about half its genes in common with George. The researchers even suggested that George may have full relatives on the same island.

The potential salvation of George's species, the Pinta tortoise, began in 1994. That year, the Yale team collected blood from 27 tortoises living on the slopes of mile-high Volcán Wolf, an active volcano on Isabela Island's northern end. Unlike single-species populations found elsewhere in the Galápagos Islands, the Volcán Wolf tortoises display an unusual combination of carapace shapes. Some are dome shaped, others have Lonesome George's distinctive saddle-back form, and some show characteristics of both types.

By 2002, the researchers had retrieved enough nuclear DNA and maternally inherited mitochondrial DNA from other Galápagos populations to tease out some unexpected links. The Volcán Wolf group seems to include a hodgepodge of lineages arising from multiple colonizations, while Lonesome George appears most evolutionarily related to saddle-backed tortoises on Española and San Cristóbal Islands, more than 180 miles to the southeast. Caccone speculates that some tortoises on the southern islands may have floated on the strong ocean currents that flow northwest to Pinta.

In 2003, a joint expedition by the Galápagos National Park and the Oviedo, Fl.–based Chelonian Research Institute failed to find any signs of tortoise life on Pinta Island but did uncover the skeletons of 15 former male residents. By extracting DNA from those remains and from others stashed away in museum collections, Caccone and her collaborators were able to compile a robust genetic profile of the Pinta species. Later, the researchers found a partial match in the nuclear DNA of a young male tortoise from the previously sampled Volcán Wolf population. The tortoise's mitochondrial DNA indicated that his mother had been born on Isabela. But it was clear that he had a Pinta male for a father, making him a hybrid of the two species.

"We had it all along but didn't know it until we had the new samples from Pinta," Caccone says. Because they have already uncovered one half-match among 27 Volcán Wolf tortoises out of a total estimated population of 2,000 to 8,000, she says, that "the chance of finding another hybrid, or even a pure [Pinta], is pretty high."

Caccone hopes to send three teams back to the steep volcano to collect more tortoise-blood samples next summer. If DNA tests reveal the presence of pure-blood Pintas, researchers could set up a new breeding program.
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POOL PALS. A Galápagos tortoise shares a morning swim with a white-cheeked pintail in a duckweed-covered pool in the Santa Cruz highlands.Nelson

Discovering more Pinta tortoises would be "thrilling," agrees Johannah Barry, president of the Galápagos Conservancy, "but it would probably not be critical to the restoration of the Pinta Island ecosystem." Beyond the small chance of finding enough individuals to constitute a robust population, she says, back breeding any half-relatives to recover a pure Pinta bloodline could take decades.

How a Pinta father ended up on Isabela remains unclear. A strong current runs the roughly 50-mile route from Pinta to Volcán Wolf, and historical accounts leave open the possibility that tortoises may have washed ashore after being dumped overboard by pirates or whalers.

Genetic studies may allow researchers to reconstruct the history of specific tortoise populations and to determine whether they may have long-lost relatives on other islands. Even so, Caccone warns that genetic patterns are often deceptive within endangered species. Diverse genotypes, normally a hallmark of older populations, can be rapidly depleted through human interference and result in populations with artificially youthful profiles, she says.

Tortoise tales

Millions of years before Europeans first caught sight of the Galápagos in 1535, ancestors of the islands' tortoises were likely roaming the South American continent. Mitochondrial-DNA comparisons suggest that the small Chaco tortoise found in the southern half of South America is the closest living relative of its much larger Galápagos counterparts, although Caccone believes that their common ancestor was also oversize. A combination of genetic evidence and geological estimates of when the islands were formed suggests that tortoises likely arrived no more than 2 to 3 million years ago, she says. Louis J Sheehan

As for how the animals made the 600-mile ocean voyage, the chilly Humboldt Current that flows north from the tip of South America and then west along the equator could have been a conduit. "It's a great highway," Caccone says. Whether carried along on her own or on a floating mat of vegetation, a single female laden with eggs could have founded the entire Galápagos population.
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STANDING PROUD. A Galápagos tortoise with a distinctive saddle-backed carapace poses at the Charles Darwin Research Statio.

Apart from their size and buoyancy, Galápagos tortoises can stay alive for 6 to 9 months without food or water, an evolutionary adaptation that became a curse when 17th- and 18th-century buccaneers and subsequent waves of whaling crews discovered that the reptiles would provide a plentiful and long-lasting source of meat. The logbooks of whaling ships record crew members often loading tortoises by the dozens into bilges and cargo holds, including up to 100 Pinta tortoises at a time.

At least two species went extinct. And by the early 1900s, American and British researchers had retrieved only a handful of live tortoises on Pinta, all of which were killed by the collectors or died en route to distant museums. The fate of the Pinta population remained murky until 1971, when a snail expert conducting research on the island saw a single tortoise and took a few pictures, unaware that his sighting was anything unusual. Peter Pritchard, director of Chelonian Research Institute, recalls that the researcher casually mentioned his sighting when the two were dining together. "Well, I was flabbergasted," Pritchard says.

Eventually, word reached the Charles Darwin Foundation, which receives its funding from a range of nonprofit organizations, countries, and individual donors and advises the Ecuadorean government on conservation issues. The foundation's research station launched an expedition in early 1972. Pritchard, who was studying marine turtles at the time, joined the trip to look for turtle nesting sites. By the time his boat arrived, he says, a resourceful student had already found the Pinta tortoise, and the expedition's goat hunters had tethered it to a cactus so that it wouldn't disappear.

Moving forward

In the 35 years since then, Lonesome George has been living at the research station on Santa Cruz, spurning two female tortoises from Isabela, ignoring frisky males who have provided sex-ed lessons, and spurring a barrage of speculation over what ails him in the reproduction department.

Two teams of researchers have modified plants to produce genetic material that disables critical genes in insects that eat the plants. The technique could provide a new strategy for agricultural-pest control.

Looking for a new way to protect corn plants, James Roberts with Monsanto in Chesterfield, Mo., and his colleagues turned to a mechanism known as RNA interference, in which segments of the genetic molecule RNA block the translation of information from a target gene (SN: 7/2/05, p. 7). The researchers found RNA sequences that would target critical genes in the western corn rootworm and two other related pests, and then modified corn so that it would generate those sequences.

In rootworms that fed on the modified corn, RNA from the plants shut down the target gene, stunting or killing the insects' larvae, the researchers report. Modified corn plants infested with corn-rootworm eggs suffered less root damage than did normal corn.

In the other study, Xiao-Ya Chen and his colleagues at the Chinese Academy of Sciences in Shanghai used a similar trick to increase the cotton bollworm's sensitivity to gossypol, a defense chemical produced by the cotton plant.

Although large doses of gossypol stunt the growth of bollworm caterpillars, the pests can tolerate the chemical at low concentrations. Chen and his colleagues found the insect gene responsible for this tolerance, and then modified Arabidopsis, a widely used lab plant, to produce silencing RNA for that gene. Insects that feasted on the modified lab plants ingested the RNA, and stopped growing when fed gossypol. The researchers are trying to reproduce their results with cotton plants.

Both teams report their findings in the November Nature Biotechnology.

Previous research had shown that RNA injected into insects could shut down specific genes. The critical innovation of the new work is oral delivery of the silencing RNA from plant to insect, Roberts says.

The Monsanto researchers "have produced protection of a crop plant against a real pest," says Peter Waterhouse of CSIRO Plant Industry in Canberra, Australia. Although the Shanghai-based study uses a model plant to deliver the RNA, it "has a very ingenious strategy ... to kill off the insects' counterdefense against a defense chemical," he adds.

For many years, farmers have planted crops engineered to possess a bacterial gene that produces an insect poison known as Bt. But this poison doesn't work on all insects, and scientists worry that pests could eventually evolve resistance to it (see Spying Genetically Engineered Crops).

With the appropriate choice of target gene, "in principle, the [RNA] strategy is applicable to any herbivorous insect," Chen says. And the ability to carefully design the RNA sequence could allow researchers to evade insect-resistance strategies, Waterhouse says.

More research will be needed to show how applicable the technique is to other pests and how well it would work in the field, he adds. Government regulatory bodies would have to grant permission before such crops could be grown in open fields. But Waterhouse says the initial results suggest that RNA interference could be a powerful strategy for controlling insect pests. Louis J Sheehan

The percentage of foreign fish in rivers is strongly linked to nearby economic activity, according to a new study of 1,055 river basins worldwide. Nonnative plants and animals can outcompete local species and damage ecosystems, sometimes to the point of collapse.

Freshwater fish can't readily move from one river basin to another on their own, so the distribution of invasive fish ought to reflect human influence, says lead researcher Sébastien Brosse of the Laboratory of Evolution and Biological Diversity in Toulouse, France. Local measures of economic activity, such as gross domestic product, account for about 70 percent of the distribution of foreign fish, supporting the idea that human activity is largely to blame, Brosse's team reports in the February PLoS Biology. Red indicates greater than 25 percent invasive fish; orange, 5 to 25 percent; and yellow, less than 5 percent. Louis J Sheehan