Like many species that migrate across a vast ocean, pinpointing all the possible causes of their decline is difficult and figuring out where conservationists might be able to intervene on their behalf is hugely challenging. But a major effort to tag and track leatherbacks that nest on the Pacific coast of Costa Rica has yielded unprecedented insight into their behavior. While most sea turtles, including other populations of leatherbacks, have widely varied dispersal patterns as they fan out across the ocean from the beaches where they nest, the leatherbacks from the beaches at Playa Grande have been found to consistently follow a relatively narrow corridor out into the sea, past the Galapagos Islands and across the equator to an area in the South Pacific where they linger at length. This discovery could be the key to the leatherbacks’ salvation.

“Given that the turtles seem to move in a predictable way from the nesting beach through the equatorial region from roughly February through April, we could potentially suspend fishing in certain areas while the leatherbacks are passing through that part of the eastern Pacific,” said George Shillinger, doctoral candidate in biology at Stanford University’s Hopkins Marine Station.

By taking the new data correlating turtle movements with various environmental features along their route and comparing that with the timing of fishing activity in the different areas the turtles travel through, the researchers can pinpoint the times and places where turtles are at the highest risk-thus providing new opportunities for improved management of the leatherback population.

Shillinger is the first author of a paper published in PLoS Biology and part of a large team of biologists and physical and biological oceanographers from the United States, France and Costa Rica who worked on the multiyear study.

The leatherback tagging study is part of the Tagging of Pacific Predators (TOPP) program, which has tagged other animals including the white shark, bluefin tuna, black-footed albatross and elephant seal. TOPP is part of the Census of Marine Life, a global network of researchers in more than 80 nations engaged in a 10-year scientific initiative to assess and explain the diversity, distribution and abundance of life in the oceans.

Over three field seasons, from 2004 to 2007, Shillinger, co-author Bryan Wallace (Duke University and Conservation International) and a team from Playa Grande National Park outfitted 46 females on the beach with small tags that emitted signals that were picked up by satellites, enabling the team to track the turtles’ location.

Shillinger and his colleagues worked with research oceanographers and co-authors Steve Bograd and Helen Bailey at the National Oceanic and Atmospheric Administration and Daniel Palacios, also at NOAA but from the University of Hawaii. They examined turtle speeds and movements in relation to the distribution and strength of the equatorial current system and found that the turtles increased their speeds as they moved through high-energy areas.

But how much of the turtles’ trajectory was from being pushed around by the currents and how much was the result of their own free will, they couldn’t tell until French oceanographer and co-author Philippe Gaspar analyzed the data using a method he had developed to make that distinction. Once the effect of the currents had been factored out, the turtles were found to be consistently heading in a south-southwesterly direction.

Year after year, the track was remaining the same. Not only were the turtles heading in the same direction, they were actually trying to follow an even narrower path than the raw data showed. As Bograd put it, “They definitely had a place they wanted to go.”

That place is the South Pacific Gyre, a vast region considered a relative desert among the world’s oceans. So why go there if it’s so barren?

“That’s still a big puzzle as to why they choose to go to this region,” Palacios said.

The only data available are satellite images showing the color of the sea. Researchers interpret greener water to be richer in chlorophyll, which is considered the foundation for the ocean food chain. Thus, the relative abundance of chlorophyll is inferred to indicate the relative richness of a fishery. Satellite images show very little green in the South Pacific Gyre.

But, satellites can only penetrate about 25 meters below the surface in the gyre. “Maybe the turtles are targeting something that is deeper in the water column,” Palacios said.

“What are they doing there is a big question,” Shillinger said. “Perhaps the tremendous water clarity may work to the advantage of these leatherbacks because they are visual predators,” he said. “They can spot little specks of white out in the deep blue sea.” Leatherbacks dine exclusively on gelatinous zooplankton, such as jellyfish.

Shillinger also said that there is a substantial longline fishery in that area, for bigeye and yellowfin tuna. “Obviously, the fish are eating something and it’s something we’re not picking up in chlorophyll signatures from satellite imagery,” he said.

Given that leatherbacks have been recorded diving as deeply as 1,280 meters, they have ample choice as far as where in the water column they choose to feed. And considering that they can grow to over 6 feet in length and weigh up to 2,000 pounds, it seems like a safe bet that they’re feeding on something.

The presence of the longline fishery in the South Pacific Gyre may be one of the reasons for the steep decline of the leatherbacks, according to Shillinger. Longliners going after fish such as tuna sometimes hook turtles. This unintentional bycatch can take a heavy toll on a species.

“What often happens with longliners is that it is just inconvenient to hassle with a turtle and they don’t want to lose the hook, either, so what people will do is just cut the flipper off with a machete and just send the turtle away to die,” he said. “A turtle without a front flipper is a dead turtle.”

Shillinger said there may also be another reason for the leatherbacks’ population crash, one not so obvious from their data.

There was one turtle that didn’t follow the migration route to the South Pacific Gyre. Instead, it swam south along the coast of Central America, where it stayed for the entire time the tag was working, 588 days.

“It seems logical that turtles would want to move along the coast, because these are highly productive regions, where they don’t have to work as hard to find food,” Shillinger said. Even though only one of the 46 subjects of the study cruised the coastal areas, he said it might be a rare survivor of a larger population that used to swim in the coastal area, but could have been hit hard by human fishing pressure in the near shore areas. Gillnets and longlines are major threats to turtles in these areas.

Shillinger says they won’t be able to answer that question until they have gathered more data, since very little current data exists about bycatch in these coastal fisheries. As the tags are designed to degrade and fall off, the researchers haven’t been able to capture the turtles’ movements beyond about two years. He suggests that turtles returning to Costa Rica from the South Pacific Gyre may turn out to be using the near shore habitats on their return.

Some progress in helping the leatherback population on the beaches of Playa Grande has already been made. Local villagers used to harvest the turtle eggs quite heavily, but owing to efforts on the part of pioneering leatherback researcher and coauthor Jim Spotila (Drexel University), the Leatherback Trust, and staff and volunteers from the Costa Rican Ministry of Environment and Energy, that practice has been halted locally. People who once collected eggs are now paid to protect them and tourists have been coming to see the turtles. “Turtle tourism has emerged as an alternative economy and now there is a real focus on protecting this beach,” Shillinger said.

But, noting that there is still intense pressure to develop Playa Grande and that some illegal development is ongoing, Shillinger added, “This beach is more or less the last stand for nesting leatherbacks in the eastern Pacific, so if this beach goes, it’s going to be a real blow.”

Shillinger and his colleagues are cautiously optimistic about the impact their new data about the migration routes could have on bolstering the leatherbacks’ survival rate.

“Being able to see these migratory corridors is something we only dreamed of when we started the project,” said co-author Barbara Block, the Charles and Elizabeth Prothro Professor in Marine Sciences at Hopkins Marine Station. Block is one of the researchers on the TOPP team and is Shillinger’s doctoral adviser.

The level of detail the researchers obtained about when the turtles are in a particular area along their route means it could be possible to have a major impact on reducing turtles lost at sea to bycatch just by temporary closures of certain areas. Temporary closures are likely to be much more palatable than long-term ones to the various nations and regulatory agencies that would have to agree on any closures for them to be effective.

And because the turtles’ migration route crosses international boundaries, it is vital to have international cooperation.

“It is still at the early stage globally, putting together large transboundary, transnational plans for protecting highly migratory species like turtles,” Shillinger said. “First and foremost, you need political will and a framework in which to operate.” International conventions have produced agreements on the need to protect many endangered ocean species, and Shillinger said that as constituents become aware of the situation and lobby their politicians, governments slowly begin to take action. But the critical part is having solid science to serve as a basis for developing any agreements.

In his efforts to bring the plight of the leatherback populations in the Pacific Ocean to people’s attention, Shillinger teamed up with Stanford MBA graduate Mark Breier to create and launch the Great Turtle Race, largely facilitated by TOPP and coordinated by the Leatherback Trust. In this educational project, a race among leatherback turtles across the Pacific Ocean is simulated using real data from the tagging project. This year’s race, the second annual, ended in June and for the first time included data from leatherbacks that started from Indonesia, in addition to those starting from the Americas.

“I wouldn’t write these turtles off. If we can inform and change fisheries practices with sound science and policy, then hopefully there will be a chance to conserve turtles and the ecosystems that they occupy,” Shillinger said. “These turtles could be a really awesome flagship for conservation.”

Major funding for this research was from support for the TOPP program (a field program of the Census of Marine Life), UNESCO and the Global Conservation Fund of Conservation International. Additional funding came from Drexel University, Goldring Biology Station, the Leatherback Trust and the supporters of the Great Turtle Race.

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“This discovery is an archaeological sensation,” commented Norbert Müller of the Johannes Gutenberg University Mainz. The research project extended over several weeks before being completed in the middle of May 2008.

Prior to this, the hippodrome had only been known from written sources. Archaeologists had failed to locate its actual site. This is surprising, as German archaeologists have been continuously excavating the site of where the ancient olympiad was held since 1875; this research has become a tradition and innumerable archaeologists, historians, and sports historians from all over the world have been involved in trying to solve this secret for over a hundred years.

Pausanias, a travel writer of the ancient world, described this course for horse races, its starting mechanisms, turning points and altars in much detail in the 2nd century AD: “If you climb over the stand of the stadion along the side where the hellanodikai are seated, you reach a terrain, where the horse races and the starting mechanism for the horses are located. The starting mechanism has the form of the prow of a ship, with the tip pointing to the race-track. Along the side where the prow touches the column of Agnaptos, it is broad. At the farthest tip of the prow there is placed a bronze dolphin on a pole (11) Both sides of the starting mechanism are more than 400 feet long and there are starting gates incorporated in them.

These starting gates are assigned by lot to the competitors in the horse races. A cable is stretched out as starting barrier before the chariots or the ridden horses. An altar of unbaked brick, plastered on the outside, is constructed every Olympiad in the centre of the prow. (12) On the altar there is an eagle with outstretched wings. The race director operates a device inside the altar. When it is put into motion, the eagle flies up, so that it is visible for the spectators, and the dolphin falls to the ground. (13) The first cables to fall down are those on both sides of the column of Agnaptos and the horses in these positions leave first.

They now draw level with those who have drawn the lot for the second place and the starting ropes are lowered here; this procedure continues until all the horses are level in a row at the tip of the prow. At this point the drivers can begin to demonstrate their skills and the speed of their horses. (14) It was Kleoitas who invented the starting device and he was so proud of his invention that his statue in Athens bears the following inscription: “The first inventor of the starting mechanism for horses at Olympia made me: Kleoitas, son of Aristokles.” It is said that a certain Aristeides modified this invention. (15) “The racecourse has one side longer than the other, and on the longer side, which is an earthen bank, there can be found, at the passage through the bank, Taraxippos, the Horse-Frightener.” (Pausanias VI 20.10-15)

Another - previously unheeded - written source from the 11th century AD goes so far as to state the size and dimensions of the enclosure: “The olympiad has a course for horse races that [has a length of] 8 stadia. Each of the long sides is 3 stadia and 1 plethron long, while the width to the starting gates measures 1 stadion and 4 plethra, [a total of] 4800 feet. Near the Taraxippos, behind which - so it is said - there is concealed an ancient hero, the horses run around a turning post; the finishing point of the race, however, is the pillar of Hippodameia. Among the horses, those in the foal category run a distance of 6 stadia, while those in the adult category run 12 stadia; chariots with a pair of foals travel three times around the circuit and those with adult horses eight times; chariots with four foals complete a total of eight circuits, while those with four adult horses complete 12 circuits.” (Tabula Heroniana II, Fol. 27f.)

To date, it had been assumed that nothing of the hippodrome had survived, as the area described by Pausanias to the east of the sanctuary of Olympia has been flooded by the Alfeios River since ancient times and has become covered with silt. In modern plans and descriptions it is usually stated quite simply that “nothing remains of the hippodrome due to flooding in medieval times”.

This served as an additional incentive for the German researchers: Using modern geophysical methods, they systematically searched the area for the first time. The experts Armin Grubert (Mainz) and Christian Hübner (Freiburg), who specialize in the use of geomagnetic and georadar techniques, were able to map soil disturbances such as water courses, ditches, and walls. Conspicuous, rectilinear structures were indeed discovered along a stretch of almost 1200 meters. The researchers believe this to be the racecourse, which ran parallel to the stadium. Structural remains identified as the temple of Demeter that is known to have been sited near the hippodrome were discovered in the northern part of the area investigated in the spring of 2007.

Of particular interest is the fact that at the halfway point of the northern access to the starting-gates - where Pausanias describes entering the hippodrome - there is a circular arrangement with a diameter of about 10 meters, clearly marked in the ancient soil layer, which could be the remains of the sacred structure described here by the ancient writer. The actual starting-gates, with boxes for up to 24 teams of horses, are most probably located under a gigantic pile of earth excavated by the archaeologists investigating the temple area since 1875.

The investigation of the area east of the sanctuary of Olympia, only made possible by the research funds provided by the Institute of Sports Science of the University of Mainz and the International Riding Association, has produced the first concrete indications of the location of the racecourse and its geographical dimensions.. Ten students were on hand to assist the sports historian Professor Norbert Müller, who is an authority on Olympia. “The DAI, with its branch in Athens, has done sports history a great service through its contribution,” said Müller. “The project could become a new attraction for the sports world, similar to the excavation of the ancient Olympic stadium 50 years ago.”

The area east of the sanctuary of Olympia had not been the subject of archaeological investigation before, although the ancient written sources show that this must have been the site of the largest construction, in area terms, built to host competitions. According to Pausanias, the hippodrome lay south of the now researched and reconstructed stadium, and must now be several meters below the current level. It is only here, between the adjoining hills on the other side of the road to Arcadia in the north and the bed of the Alfeios River in the south (which has since been straightened) that the topology is suitable for the accommodation of a racecourse with a length of more than one kilometer.

Nevertheless, the geological and geographical conditions are not favorable. On the one hand, intensive agricultural use has produced stark changes to the historical geography, and, on the other hand, the course of the Alfeios River, which once meandered through the plain, has changed several times over the centuries. The landscape in this area has changed so much that it is nearly impossible to reconstruct its appearance in ancient times. It is known today that the level of the river in medieval times was about 9 meters higher than in ancient times, but that about 7 meters of the deposited material has since been eroded and carried away by the river. This means that the ancient remains to the east of the sanctuary lie about 2 meters below the current level.

The racecourse described in such detail by Pausanias (Book VI 20.10-15) was located at this level. According to this author, the teams lined up in the shape of a prow of a ship in starting-gates in front of a hall; the starting signal was a brass eagle that was raised and lowered by means of a hoisting mechanism, while a dolphin figure moved in front of the drivers. There was space for spectators along a wall on the southern side and along the adjoining hills to the north, but it seems that there were no stone stands similar to those of the great circuses in Rome or Carthage.

Various reconstructions have been based on Pausanias’ description, with the racecourse usually assumed to be twice as wide as the starting-gates. However, it was only after a hand-written medieval document from the 11th century was correctly reinterpreted by J. Ebert in 1989 that the actual appearance and dimensions of the hippodrome became apparent. The complex had a length of 1052 meters and a width of 64 meters, not including the earth walls built for the spectators. The starting-gates stretched the full width of the racecourse.

Modern geomagnetic methods were used by a team of German scientists in April/May 2008 to explore the accessible terrain at the level described above. Two different physics-based techniques were used. Geomagnetic mapping of archaeological structures involves the accurate, high-resolution recording of the tiny magnetic anomalies in the earth’s magnetic field that these cause. Such anomalies are usually caused by the presence of foundations, large stone objects or burnt layers. This technique was used in combination with georadar, a ground penetrating form of radar. In this electromagnetic technique, short impulses that each last only a few nanoseconds are radiated into the ground. These are reflected by the margins of different layers and by objects. A combination of the two methods can be used to detect anomalies and even to determine at what depth they are located in the ground. This makes it possible to determine within which layer (modern, medieval, ancient) the identified anomalies are probably located.

An area of 10.5 hectares was finecombed with geomagnetic mapping techniques, while georadar was used to investigate an area of 3.6 hectares. It was not always possible to penetrate the thick layers of fine sand, while the remains of decades of agriculture in the form of fences, channels and concrete structures also made results difficult to interpret.

Nevertheless, some significant finds were made. It appears that there was never extensive construction on the site. The innumerable channels extending to the northern perimeter of the area once defined the edges of terraces or water drainage conduits. The Alfeios River would have repeatedly flooded the entire area up to the foot of the hills. As the ancient level is approximately 2 meters below the current level, however, any remains will have been protected to some extent. This means that the parallel anomalies (ditches, walls, earthworks) identified along a length of almost 200 meters must represent the remains of the ancient hippodrome.

The hippodrome was thus sited parallel to the stadium and ended where there is a distinctive bend in the modern road at its eastern turning point. Approximately half-way along the northern access route to the starting-gates - where Pausanias entered the hippodrome - a circular stone formation with a diameter of about 10 metres was found in a layer dating from ancient times. Some remains that were most probably once buildings located on a terrace have been discovered near the road on the northern side of the hippodrome. As remains of a temple of Demeter have been discovered by Greek archaeologists in the immediate vicinity underneath the modern road, it now seems likely that this was the location described by Pausanias.

Hence, without any need for excavation, modern geomagnetic techniques have given us the first clear indications of the site of the hippodrome east of the sanctuary of Olympia. This means that archaeological and sports-historical research has come a little closer to solving one of the last great mysteries of Olympia.

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“We have a novel approach to cancer. We know the initiating step,” said Ercole Cavalieri, Ph.D., of the University of Nebraska Medical Center. “We think prevention of cancer can be solved by eliminating this initiating step.”

Eleanor Rogan, Ph.D., a UNMC research collaborator, continued: “We have found the first step that starts a cell down the road to becoming a cancer cell. By preventing this first step from happening, we think we can stop the development of breast or prostate cancer. The combination of an early detection test for cancer risk with administration of preventing agents should enable us to significantly reduce the number of women and men that develop breast or prostate cancer.”

The researchers have discovered that certain estrogen derivatives (metabolites) can react with deoxyribonucleic acid (DNA) to cause damage that may initiate a series of events leading to breast, prostate and other cancers. They found evidence in a simple urine test in humans. Estrogens can initiate cancer when natural mechanisms of protection do not work properly in the body, allowing estrogen metabolites to react with DNA.

“If these protections are insufficient, due to genetic, lifestyle or environmental influences, we think cancer can result,” Dr. Cavalieri said. “Now that we have the basic knowledge about this unifying mechanism of cancer initiation, we have a greater sense of urgency to assess people at risk and, at the same time, begin studies of prevention by using specific natural compounds.”

The findings are published in the December issue of the International Journal of Cancer. Findings were confirmed in a second, larger study and presented at a recent gathering of international scientists and physicians in San Antonio, Texas. The study involves researchers at the University of Nebraska Medical Center, Mayo Clinic and the Italian National Cancer Institute. A majority of the study was funded by the U.S. Army Breast Cancer Research Program Center of Excellence Award. Similar findings were reported and published about prostate cancer in the journal The Prostate in 2006.

The screening test developed by the researchers analyzes estrogen metabolite profiles in humans and can simultaneously associate the profile with risk of getting breast cancer. It involves testing a one-ounce sample of urine using a sophisticated method called tandem mass spectrometry, which analyzes about 40 estrogen-related compounds, including estrogen-DNA adducts formed by a chemical reaction of estrogen metabolites and DNA.

Researchers say the results are exciting because they show women at high risk of breast cancer can be identified by the level of adducts in a urine sample.

Researchers analyzed estrogen-DNA from 46 women with normal risk for breast cancer, 12 women at high risk of developing breast cancer, and 17 women diagnosed with breast cancer. They found women at high risk of breast cancer and the women with breast cancer had significantly higher levels of the estrogen-DNA adducts in their urine samples, while the women with normal risk for breast cancer had low levels.

“This is a very big step because we have a test in humans to determine the risk of getting breast or prostate cancer long before the tumor appears,” Dr. Cavalieri said. “We can use these estrogen-DNA adducts as a measure of cancer risk. In addition, we have begun to establish how effective natural compounds may be at preventing cancer by determining their ability to reduce the levels of these adducts in urine.”

He also said accumulating evidence suggests that specific metabolites of estrogens, if abundantly formed, can become cancer-initiating agents by reacting with DNA and generate mutations leading to cancer. DNA is composed of four bases, called adenine, guanine, cytosine and thymine, the alphabet of genetic information.

Estrogen metabolites react predominantly with the first two DNA bases, adenine and guanine, to form estrogen-DNA adducts, Cavalieri said. The resulting damage generated by the reaction can give rise to mutations that eventually initiate cancer. The important estrogen-DNA adducts spontaneously fall out of the DNA, leaving behind gaps that generate the cancer-initiating mutations.

The estrogen-DNA adducts eventually make their way out of cells and are excreted in urine.

“This finding identifies a new biomarker in the urine which appears to correlate with a women’s risk of developing breast cancer,” according to Kenneth Cowan, M.D., Ph.D., director of the UNMC Eppley Cancer Center. “While these studies need to be confirmed in a prospective study in a larger group of patients, this could become an important screening assay for women and could lead to new therapies to prevent breast cancer.”

Dr. Cavalieri said one of the major obstacles in cancer research is related to the concept that cancer is a problem of 200 diseases, a viewpoint that has impeded researchers from looking at the origin of cancers because the search would be prohibitively complex. And for this reason, he said, the origin of breast, prostate and other human cancers has been virtually unknown.

While the expression of various cancers coincides with the concept of 200 diseases, some scientists believe a common origin is a factor for many prevalent types of cancer. There is widespread agreement in the scientific community that cancer is triggered by genetic mutations in critical genes, he said.

Jose Russo, M.D., senior member from the Fox Chase Cancer Center in Philadelphia, said: “The article is the best example of translational research. They have generated a unified concept of carcinogenesis and obtained a practical marker detectable in the urine of breast cancer patients. This article provides the adequate setting to explore this concept further by laying the basis to prepare a set of prospective clinical trials testing the preventive effects of the agents or mixtures of agents that can intercept the initiation event in breast or other cancers.”

David G. Longfellow, Ph.D., president and chief executive officer of the Toxicology Forum, an international, nonprofit organization devoted to conducting open dialogues among various segments of society concerned with problems in toxicology, said the work represents a paradigm shift in detection of cancer risk in humans and provides the earliest possible rational marker for prevention strategies and regimens.

“This work conveys a very exciting message that breast and prostate cancer risk can be identified years before the development of a tumor and suggests that natural preventive agents may be effectively used to prevent the initiation step in cancer,” Dr. Longfellow said. “Although this is a single manuscript, it is based on an extensive body of work in animal models and humans which consistently supports these findings and is complemented by collaboration with many international cancer scientists.”

Journal article abstract: http://www3.interscience.wiley.com/cgi-bin/abstract/117869053/ABSTRACT.

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