By Pam Eastlick
Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.
Greetings everyone and welcome to the last column of the year. I thought today we’d take a little trip through the animal file and see what we can find about the critters that share our world with us.
One critter I can definitely do without is the mosquito. Besides the fact that the mosquito is annoying and painful, it’s also a notorious spreader of disease. Quite frankly, I personally think we’d be better off without them. Here’s a sad little tale of economics and pests.
TAKING OUT THE STING
After searching for more than 50 years, scientists finally have discovered a number of new mosquito repellents that beat DEET, the gold standard for warding off the pesky insects. They sound like a dream come true. They repel mosquitoes for up to three times longer than DEET, the active ingredient in many of today’s insect repellents. They don’t have the unpleasant odor of DEET. And they don’t cause DEET’s sticky-skin sensation. But there’s a mosquito in the ointment: The odds appear to be stacked against any of the new repellents ever finding a place on store shelves.
Ulrich Bernier, Ph.D., the lead researcher for the repellent study, said that costly, time-consuming pre-market testing and approval is a hurdle that will delay the availability of the repellents, which were discovered last year.
Making the repellents commercially available takes significant investment in both money and time. The cost may be several hundred thousand dollars. Once it’s determined that the repellent works then there’s also a toxicological hazard evaluation involving numerous toxicological tests."
If the repellents continue to work well when tested in the laboratory on human skin, and if they pass the battery of toxicological tests, they still face a series of tests to prove their effectiveness against mosquitoes.
Bernier and his team discovered the repellents with what they say is the first successful application of a computer model using the molecular structures of more than 30,000 chemical compounds tested as repellents over the last 60 years. Using 11 known compounds, they synthesized 23 new ones. Of those, 10 gave about 40 days protection, compared to 17.5 days for DEET, when a soaked cloth was worn by a human volunteer. When applied to the skin, however, DEET lasts about five hours.
Bernier routinely participates in repellency studies, which involve about 500 mosquitoes trying to land on his arm and bite through a repellent-soaked cloth. If the mosquitoes don’t land, the researchers know the repellent is working. If they walk around on the cloth-covered-arm, they’re on the verge of being repelled. If they bite…then it’s on to the next repellent.
To search for the best repellents, the team devised software that recognized structural features of a chemical that would make it effective in keeping the bugs away. They trained it by feeding it the molecular structures of 150 known repellents. Based on this information, the program learned to identify the chemical traits of a good repellent without the chemists even having to know what those traits were. For example, the team checked out 2,000 variants of a compound found in black pepper that repels insects.
I hope that they get some funding to market these new repellants soon. I’d sure buy them!
Mosquitoes stay away from repellent-soaked cloth on the arm of researcher Ulrich Bernier. (Credit: Greg Allen, U.S. Department of Agriculture, Agricultural Research Service)
And now we move on to a tale of another of the least-loved animals on the planet.
YOU THINK WE’VE GOT PROBLEMS??
I’m having a little mini-invasion at my house. I’m surrounded by forest and a large family of brown tree snakes seems to have decided to call my house and my dog food theirs. We whip them around a mop handle and dump them in the freezer. No more blood, no more machete nicks on my stuff. It’s a humane way to die, not that I really care because brown tree snakes are aggressive and I’ve been bitten several times.
Brown tree snakes can get quite large, but they don’t hold a candle to the subjects of this story. The southern United States is being invaded by some of the biggest snakes on the planet.
A new report by the U.S. Geological Survey (USGS) tells all about the risks of nine non-native snake species including boa constrictors, anacondas and pythons. Two of the species have been documented as reproducing in the wild in South Florida where the Burmese python population is already reported to be in the tens of thousands.
Although the giant snakes don’t pose a great threat to humans, adults of the largest pythons have been known to attack and kill people in their native habitats. The snake most often associated with attacks on humans is the reticulated python, a native of Southeast Asia.
Although many of the giant snakes snake species may be confined to the deep South, others like Burmese pythons, northern and southern African pythons, boa constrictors and yellow anacondas put larger portions of the U.S. mainland at risk.
The USGS scientists who authored the report point out that native U.S. birds, mammals, and reptiles have never had to deal with huge predatory snakes before. Individuals of the largest three species reach lengths of more than 20 feet and upwards of 200 pounds. The reticulated python is the world’s longest snake, and the green anaconda is the heaviest snake. Both species have been found in the wild in South Florida, although breeding populations are not yet confirmed for either.
Breeding populations have been confirmed in South Florida for Burmese pythons and the boa constrictor, and there is strong evidence that the northern African python may have a breeding population in the wild as well.
Unfortunately these snakes mature early, produce large numbers of offspring, travel long distances, and have broad diets that allow them to eat most native birds and mammals. In addition, most of these snakes can inhabit a variety of habitats and are quite tolerant of urban or suburban areas. Boa constrictors and northern African pythons, for example, already live wild in the Miami metropolitan area.
The report notes that there are no controls adequate for eradicating an established population of giant snakes once they have spread over a large area. Making the task of eradication more difficult is that in the wild these snakes are extremely difficult to find since their camouflaged coloration enables them to blend in well with their surroundings.
Dr. Gordon Rodda, a herpetologist who lived on Guam, mentions us in the report. “We have a cautionary tale with the American island of Guam and the brown tree snake,” he says. “Within 40 years of its arrival, this invasive snake has decimated the island’s native wildlife: 10 of Guam’s 12 native forest birds, one of its two bat species, and about half of its native lizards are gone. The python introduction to Florida is so recent that the tally of ecological damage cannot yet be made.”
USGS researchers used the best available science to predict areas of the country most at risk of invasion by these giant snakes. Based on climate alone, many of the species would be limited to the warmest areas of the United States, including parts of Florida, extreme south Texas, Hawai
i, and America’s tropical islands, such as Puerto Rico, Guam, and other Pacific islands. For a few species, however, larger areas of the continental United States appear to exhibit suitable climatic conditions. For example, much of the southern U.S. climatic conditions are similar to those experienced by the Burmese python in its native range.
The Fish and Wildlife Service and the National Park Service will use the report to help them figure out what to do about the problem and how to prevent further colonization.
Researchers implant a radio transmitter in a 16-foot, 155-pound female Burmese python at the South Florida Research Center, Everglades National Park. Radio-tracking builds understanding of where pythons spend their time and therefore where they can be controlled in practice. Photo courtesy of Lori Oberhofer, National Park Service. (Credit: U.S. Geological Survey)
I once had a very good friend in Pete, the reticulated python. Despite her name, she was a female and she was a mascot for one of the units at U-tapao Air Base in Thailand. She had been captured on the flightline about five years before I got there and at that time, she was three feet long and weighed 30 pounds.
To keep Pete fed, the Thais who ran the café where she was housed ran a lottery. They put a chicken in the cage with Pete once a week and for a quarter, you could put in your guess of the day and time that Pete ate the chicken. The person who came the closest got the money, less the amount to buy the next week’s chicken.
Reticulated pythons don’t eat that often in the wild and when I left Thailand, Pete was 33 feet long and weighed 300 pounds. Most times, when I came to call, she would rear up her head until it was on the level of mine and we would chat. I never decided if she was just curious about the white lady, or viewed me as lunch. She was an impressive animal, but not one I’d want to meet in my back yard!
By Pam Eastlick
Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond. Visit our website at www.thedeepradioshow.com
As many of you know, in addition to writing The Deep column I’m also the Star Lady. And in my capacity as Planetarium Director, I’d like to invite you to the UOG Planetarium this Thursday, Friday or Saturday for the Planetarium show “Winter Skies” which tells you all about the things you can find in Guam’s lovely dry-season skies. The doors open at 6:00 p.m. and the show starts at 6:30 p.m.
After “Winter Skies” we’ll have “Quality Time with the Star Lady” where I answer your space-related questions until it gets dark enough that we can go outside and try to find some the sky objects in the real sky (I call it “The BIG Planetarium!). So join us this weekend for “Winter Skies” and remember the show is FREE!
As we all struggle to get back into the daily grind after the holidays, I thought I’d share some news items about Mother Earth: specifically about her geology.
FLIPPING POLES
One of the things you learn when you study space and the Earth is that while we humans live our lives in minutes, days and years, the average human life span is not even a blink of the eye in recorded time (see my article Time Is (As) Money.) When I talk about a ‘recent event’, I’m probably talking about last year or perhaps something that happened in the 1990’s. When a geologist talks about something that happened recently, the event could have occurred a hundred thousand year ago.
Last week, I talked about a research team that was examining the Mid-Atlantic Ridge. The first cores drilled there pointed the way to one of the most dramatic discoveries of the 20th century. The Mid-Atlantic Ridge is a long chain of volcanoes that are constantly active. The molten rock flows down the mountainside and eventually hardens. This astounding flow is pushing the Americas away from Europe and Africa and eventually, the Atlantic will be wider than the Pacific.
Earth has a large magnetic field, which is generated by a big core of molten iron at the Earth’s center. When the scientists examined their cores from the Mid-Atlantic Ridge, they discovered something really interesting. The rocks contained iron, just as they expected, but some of the magnetized rock didn’t point north; it pointed south. When they mapped the pole reversals with their distance from the spreading center (the active volcanoes) they constructed a map of pole reversals frozen in the rock layers.
Earth’s poles have ‘flipped’ at least 400 times over the last 180 million years. The time intervals between the ‘flips’ vary wildly from 50,000 years to 40 million years. The ‘average’ interval is about 500,000 years.
The most recent reversal occurred about 780,000 years ago. This is longer than ‘average’ (but nowhere near 40 million years) and scientists have found some clues that we may indeed be at the beginning of another pole reversal.
Scientists have recently discovered a shallow core field in the Earth’s magnetism. They believe the shallow core field may play a role in determining whether the main field polarity flips while weakened or whether it recovers its strength without reversing. Current evidence suggests we are now approaching one of these transitional states because the main magnetic field is relatively weak and rapidly decreasing, he says. While the last polarity reversal occurred several hundred thousand years ago, the next might come within only a few thousand years.
Right now, historic records show that the strength of the magnetic field is declining very rapidly. Anomalous magnetic ‘poles’ have formed in widely separated spots from Brazil to Siberia. We all know that a compass doesn’t point to due north, it points to ‘magnetic north’. And the pole wanders. In the 1700’s, it was in southern Canada. It’s now in northern Canada and is drifting towards Siberia at an accelerating rate. The pole was moving about 6 miles per year at the beginning of the 20th century, but the drift rate was 25 miles a year in 2003. It is also unknown if the drift will continue to accelerate.
The researchers say that if current trends continue, in 1,500 years Earth’s magnetic field will be as weak as it’s ever been and the poles will probably reverse. We certainly won’t see reversal, and neither will our grandchildren. Fifteen hundred years is a very long time for humans, but the blink of an eye for geologic history.
FINDING THE HOT SPOTS
Of course, the Mid-Atlantic Ridge isn’t the only spot for undersea volcanoes. There are other ‘hot spots’ where a plume erupts from the mantle and causes a chain of volcanoes as the sea floor drifts above it. The most famous example of this is the Hawaiian Islands. The island chain extends over thousands of miles including eroded seamounts that are below the surface of the water. The Hawaiian chain even records a right angle turn in the spreading direction millions of years ago. But Hawaii isn’t the only island chain created by a hot spot. New research shows that the Samoan Islands were created in the same way.
A new study that determines Samoa is indeed on the path of a geologic “hotspot” trail is adding fuel to a vigorous scientific debate over the origins of volcano chains – especially in the Pacific Ocean. Some scientist think they are created by hot spots, others advocate the idea that the world’s 50,000 seamounts – most of which have never been explored – may have been formed due to plate tectonic forces that locally have put the Pacific plate under stress and extension. Oregon State University marine geologist Anthony Koppers says there’s room for both theories.
“There are areas, including Samoa, where a clear linear age progression of the islands or seamounts indicates a hotspot trail, and there are areas where alternative theories make more sense,” Koppers said. “The whole debate underscores the need for more research, because these are fundamental questions about the processes that formed, and continue to form, the Earth’s crust.”
Samoa has been an enigma among scientists because the ages determined from sampled lava don’t seem to line up in a linear fashion with the movement of plates. Some scientists took that to indicate that the creation of the islands was related to magma seeping up through cracks in the seafloor in stressed fracture zones.
In their study, funded by the National Science Foundation, Koppers’ team found that previous age determination studies of the Samoan islands focused on land that had risen above sea level and was much “younger” geologically than older rocks at the base of the seamounts.
Samoa is close to the Tonga Trench, Koppers said, where the Pacific plate submerges beneath another tectonic plate and bends sharply. “The resulting stress on the plate complicates the volcanic processes,” he said.
“As we get better data sets, we’ll gain a clearer understanding of the processes that are shaping the planet,” Koppers said. “Until those models are refined, we’ll have to collect data and evaluate each seamount trail on a case-by-case basis.”
A narrow strait (just left of center) separates the two triangle-shaped islands of Ofu (left) and Olosega (right) in eastern Samoa. The islands are formed by two eroded, coalescing basaltic shield volcanoes. (Credit: Peter Craig, 1995 / U.S. National Park Service)
T
HE BIG ONE
One thing that can happen when undersea volcanoes erupt is a tsunami. We all remember the incredible devastation all along the Indian Ocean coastline only four years ago. A line of massive boulders on the western shore of the island of Tonga may be evidence of a volcano-triggered tsunami that makes the Boxing Day tsunami look puny. These seven coral boulders are up to 30 feet high and weigh up to 3.5 million pounds and they’re located 300 to 1,300 feet from the coast. The house-sized boulders were likely flung ashore by a wave rivaling the tsunami generated by the 1883 eruption of Krakatoa in Indonesia, which is estimated to have been 115 feet high.
These giant coral rocks did not form at their present location on Tongatapu, Tonga’s main island. Because the island is flat, the boulders could not have rolled downhill from elsewhere. The boulders are made of the same reef material found just offshore, which is quite distinct from the island’s volcanic soil. In fact, satellite photos show a clear break in the reef opposite one of the biggest boulders. And some of the boulders’ coral animals are oriented upside down or sideways instead of toward the sun, as they are on the reef.
The boulders are such an unusual part of the Tongan landscape that tales of their origins appear in local folklore. According to one legend, the god Maui hurled the boulders ashore in an attempt to kill a giant man-eating fowl.
Of course, we’re luck here on Guam. A tsunami is an ocean-deep wave that must enter shallow water to have the run-up necessary to cause massive on-shore destruction. If you’ve ever looked at a topographic map of the water around Guam, you’ll realize that there is NO shallow water to act as a run-up for a tsunami. We have lots of things to worry about here, but tsunamis aren’t one of them.
Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about tsunamis on Guam and many other topics. Enjoy!
