Scent Lures Mosquitoes

No More Big Stink: Scent Lures Mosquitoes, But Humans Can't Smell It

Mosquito traps that reek like latrines may be no more. A University of California, Davis research team led by chemical ecologist Walter Leal has discovered a low-cost, easy-to-prepare attractant that lures blood-fed mosquitoes without making humans hold their noses.

The synthetic mixture, containing compounds trimethylamine and nonanal in low doses, is just as enticing to Culex mosquitoes as the current attractants, Leal said, but this one is odorless to humans.

The research, published in the current edition of the Public Library of Science Journal or PLoS One, could play a key role in surveillance and control programs for Culex species, which transmit such diseases as West Nile virus, encephalitis and lymphatic filariasis.

Oviposition or gravid female traps draw blood-fed mosquitoes ready to lay their eggs, but the chemical- and water-infused traps just plain stink, Leal said. The smell is highly offensive to those monitoring the traps and to people living near them.

That prompted the UC Davis researchers to launch a multidisciplinary approach to find more user-friendly, chemically based lures for gravid Culex mosquitoes.

Their extensive field research in Recife, Brazil, a region known for its high populations of Culex quiquefasciatus, showed that a combination of trimethylamine and nonanal “is equivalent to the currently used infusion-based lure,” Leal said, “and superior in that the offensive smell of infusions was eliminated.”

The Leal lab searches for attractants in two ways. The first is the conventional chemical ecology approach or finding smells that attract mosquitoes. The second, or what Leal has coined “reverse chemical ecology,” involves studying olfaction after identifying attractants.

Mosquito populations are typically monitored with two traps: the conventional carbon dioxide traps and the gravid female trap. Mosquitoes captured in the carbon dioxide traps are less likely to be infected than those in the gravid traps.

“The gravid traps are more important for surveillance,” Leal said, “as they capture mosquitoes that have had a blood meal and thus, more opportunity to become infected.”

By monitoring gravid traps containing West Nile virus-infected mosquitoes, mosquito and vector control districts and health officials can determine when it is time to spray.

Leal said that another advantage of the gravid traps is that with the capture of one female mosquito, that eliminates not only her, but hundreds of her would-be offspring. “Each female mosquito has the potential to produce about 200 eggs, and she can have as many as five cycles. So when we capture a gravid mosquito, that can remove as many as 500 females.”

UC Davis research entomologist William Reisen said sampling Culex species in urban environments can be challenging, but the gravid trap work is crucial.

Because the Southern house mosquito, Culex quinquefasciatus, feeds on the blood of a wide variety of hosts, the West Nile virus can move rapidly through bird and human populations, according to Reisen.

“Sampling the species in urban environments has been a challenge until studies on its oviposition cues allowed the development of gravid female traps that collect mostly females that previously have blood-fed and, therefore, had a chance to become infected,” Reisen.

Leal said the compounds used in the research are “simple and inexpensive” and would be of great benefit “to not only us, but third-world countries where Culex quinquefasciatus is a problem.”

The researchers began preliminary field tests in Davis and Sacramento but when aerial sprays mitigated the levels of West Nile virus-infested mosquitoes, they set up traps in Recife, Brazil, a city endemic for lymphatic filariasis.

Scientists involved in the study with Leal were UC Davis researchers Wei Xi, Yuko Ishida, Zain Syed, Nicolas Latte, Angela Chen and Tania Morgan; Anthony Cornel, associate professor of entomology at UC Davis and director of the Mosquito Control Research Laboratory, based at the Kearney Agricultural Center, Parlier; and Rosângela M. R. Barbosa and André Furtado of the Department of Entomology, Centro de Pesquisas Ageu Magalhaes-Fiocruz, Recife, Brazil.

Monkey Population - Cambodia

Unexpected Large Monkey Population Discovered In Cambodia: Tens Of Thousands Of Threatened Primate


A Wildlife Conservation Society report reveals surprisingly large populations of two globally threatened primates in a protected area in Cambodia.

The report counted 42,000 black-shanked douc langurs along with 2,500 yellow-cheeked crested gibbons in Cambodia's Seima Biodiversity Conservation Area, an estimate that represents the largest known populations for both species in the world.

WCS scientists conducted the surveys with the Royal Government of Cambodia's Ministry of Agriculture, Forestry and Fisheries across an area of 300 square miles (789 square kilometers) within a wider landscape of 1,150 square miles (3,000 square kilometers), which is about the size of Yosemite National Park. The scientists believe total populations within the wider landscape may be considerably greater.

The WCS scientists who worked on the census include Tom Clements, Nut Meng Hor, Men Soriyun, Edward Pollard, Hannah O'Kelly, and Samantha Strindberg.

The data were first presented at the International Primatological Society Congress held recently in Edinburgh, Scotland. WCS also announced at the IPS Congress the discovery of 125,000 western lowland gorillas in northern Republic of Congo, where conservation work has been ongoing since the early 1990s.

"Whether it's protecting gorillas in the Republic of Congo or monkeys and gibbons in Cambodia, conservation can and does work when you have government commitment and scientific knowledge on the ground ," said Dr. John G. Robinson, Executive Vice President for Conservation and Science for the Wildlife Conservation Society. "Now we must put into place the management to truly protect these populations and apply the approach to other regions where primates are in trouble."

The two primate species are found in much lower numbers at other sites in Cambodia and in Vietnam. Prior to the recent discovery in the Seima Biodiversity Conservation Area, the largest known populations were believed to be in adjacent Vietnam, where black-shanked douc langurs and yellow-cheeked crested gibbons hover at 600 and 200 respectively. The total population of the two species remains unknown.

The recent census in Cambodia took place in a former logging area where the two monkeys were once extensively hunted. Then in 2002, the Minister of Agriculture, Forestry and Fisheries declared the region a conservation area and began working with WCS on site management and landscape-level planning for conservation and local development.

According to WCS, a combination of factors account for such high numbers of primates: successful long-term management of the conservation area; cessation of logging activities; a nation-wide gun confiscation program implemented in the 1990s; and habitat where there is plenty of food. The report says that the two primate populations started to recover in 2002 when the joint program between WCS and the Royal Government began and have remained stable since 2005.

The news on primates is not all good. In Cambodia, WCS researchers are concerned that looming threats could jeopardize recent successes.

"Despite this good news in Cambodia, the area still remains at risk from conversion to agro-industrial plantations for crops, including biofuels, and commercial mining," said Tom Clements, the lead author of the WCS report. "WCS is therefore committed to continuing to work with the Cambodian Government to ensure that these globally important primate populations will continue to remain secure."

WCS has worked with the Royal Government of Cambodia since 1999, helping to establish the Seima Biodiversity Conservation Area, and developing landscape-level conservation programs in the Northern Plains and Tonle Sap Great Lake.

WCS work in Cambodia has been supported by U.S. Fish and Wildlife Service's Great Apes Conservation Fund, MacArthur Foundation, Liz Claiborne Art Ortenberg Foundation, ADB Greater Mekong Subregion Core Environment Program, and the Danish Government's Danida program.

Bacteria Power

Bacteria Power: Future For Clean Energy Lies In 'Big Bang' Of Evolution


Amid mounting agreement that future clean, "carbon-neutral", energy will rely on efficient conversion of the sun's light energy into fuels and electric power, attention is focusing on one of the most ancient groups of organism, the cyanobacteria.

Dramatic progress has been made over the last decade understanding the fundamental reaction of photosynthesis that evolved in cyanobacteria 3.7 billion years ago, which for the first time used water molecules as a source of electrons to transport energy derived from sunlight, while converting carbon dioxide into oxygen.

The light harvesting systems gave the bacteria their blue ("cyano") colour, and paved the way for plants to evolve by "kidnapping" bacteria to provide their photosynthetic engines, and for animals by liberating oxygen for them to breathe, by splitting water molecules. For humans now there is the tantalising possibility of tweaking the photosynthetic reactions of cyanobacteria to produce fuels we want such as hydrogen, alcohols or even hydrocarbons, rather than carbohydrates.

Progress at the research level has been rapid, boosting prospects of harnessing photosynthesis not just for energy but also for manufacturing valuable compounds for the chemical and biotechnology industries. Such research is running on two tracks, one aimed at genetically engineering real plants and cyanobacteria to yield the products we want, and the other to mimic their processes in artificial photosynthetic systems built with human-made components. Both approaches hold great promise and will be pursued in parallel, as was discussed at a recent workshop focusing on the photosynthetic reaction centres of cyanobacteria, organised by the European Science Foundation (ESF).

A key point noted by Eva Mari Aro, the vice-chair of the ESF conference, was that there is now universal agreement over the ability of photosynthesis to provide large amounts of clean energy in future. While the sustainable options currently pursued such as wind and tidal power will meet some requirements, they will not be able to replace fossil fuels as sources of solid energy for driving engines, nor are they likely to be capable on their own of generating enough electricity for the whole planet.

Meanwhile the current generation of biofuel producing crops generally convert less than 1% of the solar energy they receive to biomass, which means they would displace too much agricultural land used for food production to be viable on a large scale. There is the potential to develop dedicated systems, whether based on cyanobacteria, plants, or artificial components, capable of much higher efficiencies, reaching 10% efficiency of solar energy conversion. This would enable enough energy and fuel to be produced for a large part of the planet's needs without causing significant loss of space for food production.

As Aro pointed out, photosynthesis evolved by cyanobacteria produced all our fossil fuels in the first place. However the rapid consumption of these fossil fuels since the industrial revolution would if continued return atmospheric carbon dioxide towards the levels at the time cyanobacteria evolved, also heating the planet up to the much higher temperatures that prevailed then.

The objective now is to exploit the same reactions so that the remaining fossil fuels can be left in the ground. Among promising contenders discussed at the ESF conference was the idea of an artificial leaf that would simulate not just photosynthesis itself but also the ability of plants to regenerate themselves. This could be important, since the reactions of photosynthesis are destructive, dismantling the protein complexes where they take place, which therefore need regular reconstruction. Under a microscope, chloroplasts, the sub-cellular units where photosynthesis take place, resemble a permanent construction site, and even artificial systems would probably need some form of regenerative capability.

A future aim therefore is to build an artificial leaf-like system comprised of self-assembling nanodevices that are capable of regenerating themselves – just as in real plants or cyanobacteria. "Fundamental breakthroughs in these directions are expected on a time scale of 10 to 20 years and are recognized by the international science community as major milestones on the road to a renewable fuel," said Aro.

Such breakthroughs depend on further progress in understanding the precise structure and mechanisms of photosynthesis, in particular the protein complex known as photosystem II, which breaks down the hydrogen atoms of water into their constituent protons and electrons to carry the energy derived from sunlight onto photosystem I, leading to production of carbohydrates and ultimately also the proteins and fats required by all organisms.

The conference "Molecular Bioenergetics of Cyanobacteria: Towards Systems Biology Level of Understanding" was held on the Costa Brava, Spain during spring 2008.

Mystery Of Young Stars Near Black Holes Solved

Mystery Of Young Stars Near Black Holes Solved

The mystery of how young stars can form within the deep gravity of black holes has been solved by a team of astrophysicists at the Universities of St Andrews and Edinburgh.

The team made the discovery after developing computer simulations of giant clouds of gas being sucked into black holes. The new research may help scientists gain better understanding of the origin of stars and supermassive black holes in our Galaxy and the Universe. The new discovery is published in the journal Science August 22, 2008.

Until now, scientists have puzzled over how stars could form around a black hole, since molecular clouds - the normal birth places of stars - would be ripped apart by the black hole's immense gravitational pull.

However, the new study by Professor Ian Bonnell (St Andrews) and Dr Ken Rice (Edinburgh) found that stars appear to form from an elliptical-shaped disc, the remnant of a giant gas cloud torn apart as it encounters a black hole.

The discovery of hundreds of young stars, of high masses and making oval-shaped orbits around a black hole three million times more massive than the sun, and at the centre of our Galaxy, is described as one of the most exciting recent discoveries in astrophysics.

Prof Bonnell comments "These simulations show that young stars can form in the neighbourhood of supermassive black holes as long as there is a reasonable supply of massive clouds of gas from further out in the Galaxy.

The simulations, performed on the Scottish Universities Physics Alliance (SUPA) SGI Altix supercomputer - taking over a year of computer time - followed the evolution of two separate giant gas clouds up to 100,000 times the mass of the sun, as they fell towards the supermassive black hole.

The simulations show how the clouds are pulled apart by the immense gravitational pull of the black hole. The disrupted clouds form into spiral patterns as they orbit the black hole; the spiral patterns remove motion energy from gas that passes close to the black hole and transfers it to gas that passes further out. This allows part of the cloud to be captured by the black hole while the rest escapes. In these conditions, only high mass stars are able to form and these stars inherit the eccentric orbits from the disc. These results match the two primary properties of the young stars in the centre of our Galaxy: their high mass and their eccentric orbits around the supermassive black hole.

Dr Rice comments " The crucial element was the modelling of the heating and cooling of the gas as this tells us how much mass is needed for part of the gas to have enough gravity to overcome its own gas pressure, and thus form a star. The heating is caused by the extreme compression of the cloud as it is squashed and pulled apart by the black hole. This is balanced by the cooling which requires detailed knowledge of how quickly the radiation can escape the cloud. "

Professor Bonnell concluded, “That the stars currently present around the Galaxy's supermassive black hole have relatively short lifetimes of ~10 million years, suggests that this process is likely to be repetitive. Such a steady supply of stars into the vicinity of the black hole, and a diet of gas directly accreted by the black hole, may help us understand the origin of supermassive black holes in our and other galaxies in the Universe."