Insecticides Lead to Starvation of Aquatic Organisms
Neonicotinoid insecticides have adverse effects not only on bees but also on freshwater invertebrates. Exposure to low but constant concentrations of these substances -- which are highly soluble in water -- has lethal effects on these aquatic organisms.
At the end of April, the EU imposed a 2-year ban on the use of neurotoxic agents belonging to the neonicotinoid group. In Switzerland, the Federal Office for Agriculture (FOAG) has followed suit, suspending the authorizations of three insecticides used on oilseed rape and maize fields. These measures have been taken in response to evidence that neonicotinoids are toxic to honeybees and are contributing to the decline of bee colonies.
An Eawag study published today in the journal PLOS ONE (Public Library of Science) now shows that at least one of the insecticides in this class also has toxic effects on freshwater invertebrates. In this study, native freshwater shrimps (gammarids) were exposed to pulsed high and to constant low concentrations of imidacloprid. Peak concentrations typically occur when rain falls on farmland during or shortly after the application of insecticides; these soluble but persistent substances can then enter surface waters via runoff. Interestingly, pulses lasting no more than a day proved less harmful to the organisms than concentrations that were much lower but persisted for several days or weeks. While organisms transferred to clean water after pulsed exposure recovered relatively rapidly, constant exposure led to starvation after 2 to 3 weeks. This was because the organisms' mobility and feeding behaviour was impaired by the neurotoxin.
The slow starvation effect observed under constant exposure to low levels of neonicotinoids is not detected by conventional toxicity tests, as they are not carried out over a period of several weeks. In addition, the study indicated that seasonal and environmental factors can be crucial: the results of the experiments are significantly affected by organisms' initial fitness and lipid reserves. To eliminate these effects and to identify processes other than starvation that influence survival rates in aquatic organisms, the research team has also developed a mathematical model which makes it possible to predict harmful concentrations and exposure times.
Brain Rewires Itself After Damage or Injury, Life Scientists Discover
When the brain's primary "learning center" is damaged, complex new neural circuits arise to compensate for the lost function, say life scientists from UCLA and Australia who have pinpointed the regions of the brain involved in creating those alternate pathways -- often far from the damaged site.
The research, conducted by UCLA's Michael Fanselow and Moriel Zelikowsky in collaboration with Bryce Vissel, a group leader of the neuroscience research program at Sydney's Garvan Institute of Medical Research, appears this week in the early online edition of the Proceedings of the National Academy of Sciences.
The researchers found that parts of the prefrontal cortex take over when the hippocampus, the brain's key center of learning and memory formation, is disabled. Their breakthrough discovery, the first demonstration of such neural-circuit plasticity, could potentially help scientists develop new treatments for Alzheimer's disease, stroke and other conditions involving damage to the brain.
For the study, Fanselow and Zelikowsky conducted laboratory experiments with rats showing that the rodents were able to learn new tasks even after damage to the hippocampus. While the rats needed more training than they would have normally, they nonetheless learned from their experiences -- a surprising finding.
"I expect that the brain probably has to be trained through experience," said Fanselow, a professor of psychology and member of the UCLA Brain Research Institute, who was the study's senior author. "In this case, we gave animals a problem to solve."
After discovering the rats could, in fact, learn to solve problems, Zelikowsky, a graduate student in Fanselow's laboratory, traveled to Australia, where she worked with Vissel to analyze the anatomy of the changes that had taken place in the rats' brains. Their analysis identified significant functional changes in two specific regions of the prefrontal cortex.
"Interestingly, previous studies had shown that these prefrontal cortex regions also light up in the brains of Alzheimer's patients, suggesting that similar compensatory circuits develop in people," Vissel said. "While it's probable that the brains of Alzheimer's sufferers are already compensating for damage, this discovery has significant potential for extending that compensation and improving the lives of many."
The hippocampus, a seahorse-shaped structure where memories are formed in the brain, plays critical roles in processing, storing and recalling information. The hippocampus is highly susceptible to damage through stroke or lack of oxygen and is critically inolved in Alzheimer's disease, Fanselow said.
"Until now, we've been trying to figure out how to stimulate repair within the hippocampus," he said. "Now we can see other structures stepping in and whole new brain circuits coming into being."
Zelikowsky said she found it interesting that sub-regions in the prefrontal cortex compensated in different ways, with one sub-region -- the infralimbic cortex -- silencing its activity and another sub-region -- the prelimbic cortex -- increasing its activity.
"If we're going to harness this kind of plasticity to help stroke victims or people with Alzheimer's," she said, "we first have to understand exactly how to differentially enhance and silence function, either behaviorally or pharmacologically. It's clearly important not to enhance all areas. The brain works by silencing and activating different populations of neurons. To form memories, you have to filter out what's important and what's not."
Complex behavior always involves multiple parts of the brain communicating with one another, with one region's message affecting how another region will respond, Fanselow noted. These molecular changes produce our memories, feelings and actions.
"The brain is heavily interconnected -- you can get from any neuron in the brain to any other neuron via about six synaptic connections," he said. "So there are many alternate pathways the brain can use, but it normally doesn't use them unless it's forced to. Once we understand how the brain makes these decisions, then we're in a position to encourage pathways to take over when they need to, especially in the case of brain damage.
"Behavior creates molecular changes in the brain; if we know the molecular changes we want to bring about, then we can try to facilitate those changes to occur through behavior and drug therapy," he added. I think that's the best alternative we have. Future treatments are not going to be all behavioral or all pharmacological, but a combination of both."
A new Red List for ecosystems
UNSW scientists have led the development of a new Red List system for identifying ecosystems at high risk of degradation, similar to the influential Red List for the world`s threatened species.
The team carrying out the research was convened by the International Union for Conservation of Nature and led by Professor David Keith, of the University of New South Wales and the NSW Office of Environment.
The study, which illustrates how the framework for risk assessment applies to 20 ecosystems around the world, including eight in Australia, is published in the Public Library of Science journal, PLoS ONE.
Professor Keith, of UNSW`s Australian Wetlands, Rivers and Landscapes Centre, AWRLC, said that ecosystems around the globe are facing unprecedented threats. This affects biodiversity and - increasingly - the services that living organisms provide to people, including clean water, and agricultural and fisheries production.
This is one of the world`s most significant conservation challenges and we really need a better system for understanding the risks to the world's ecosystems, so that we can make more informed decisions about sustainable environmental management.
Now, for the first time, we have a consistent method for identifying the most threatened ecosystems across land, freshwater and ocean environments, said Professor Keith.
One of the authors, Professor Richard Kingsford, Director of the AWRLC said: “The most encouraging thing about this initiative is that it focuses attention on the habitats of our biodiversity. We can see it applying to the hundreds, or even thousands, of species that might live in an ecosystem”.
The method evaluates multiple symptoms of risk produced by different processes of ecosystem degradation.
"Changes in the distribution of an ecosystem, its physical environment and its component species can each tell us something different about the severity of risks, and these symptoms can now be assessed in standard ways across different types of ecosystems," said Professor Keith.
The new system is flexible, enabling it to handle a range of different sources of information, depending on the specific processes driving degradation of each ecosystem.
The PLoS study illustrates the implementation of the framework using 20 case studies encompassing rainforests, wetlands, coral reefs and other major global ecosystems.
“This is a major breakthrough for the challenge of managing ecosystems more sustainably. We will be able to apply it across global, national and state boundaries for consistent state of environment reporting,” said Dr Emily Nicholson, of the Centre of Excellence in Environmental Decisions at the University of Melbourne, a co-author of the study.
Dr Jon Paul Rodriguez, at Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Venezuela, joint leader of the project for IUCN, organised an extensive international consultation process to build a strong conceptual framework for risk assessment that is well grounded in the practicalities of different ecosystems around the world.
He said the framework was a critical step towards the development of a world view of our environment and all its ecosystems, which IUCN is aiming to complete by 2025.
Influenza in Africa Should Not Be Ignored, Researchers Urge
Influenza is circulating in Africa, but virtually no information or attention is evident, says a new essay in PLoS Medicine. Maria Yazdanbakhsh and Peter Kremsner argue that the lack of adequate surveillance means that the burden of influenza in Africa is incorrectly believed to be negligible. But sporadic reports from various regions in Africa indicate that influenza is circulating and may be regularly causing epidemics
Whereas in temperate areas influenza activity displays a seasonal pattern with marked peaks in the winter, influenza is present all year round throughout the tropics. The authors say that the well-established surveillance network WHO Flu Net in place in Europe and North America, provides continuous data on influenza burden and the spread of viral types and subtypes. Recent threats of pandemic influenza have prompted similar active monitoring in parts of Southeast Asia and Latin America. But the prevalence and incidence of influenza in most tropical countries especially in Africa are largely unknown, say the authors, and improved surveillance is needed.
For example, the authors state, the WHO H1N1 swine flu update of May 2009 contained reports of infected patients in many countries, but none in Africa, whereas two reports in October 2009 confirmed swine flu cases from South Africa and Kenya. This indicates that "that the virus was circulating in Africa, but because of the lack of a rigorous surveillance system, it was not reported as readily."
'Land Grabs' For Rice Production Due To Supply Threats
Recent interest in “land grabs” or the international acquisition of land to produce rice is sparked by a looming threat of inadequate rice supplies.
To put it simply, there is not enough rice to feed the world,” says Dr. Robert Zeigler, director general of the International Rice Research Institute (IRRI).
“To meet the need and keep rice prices around US$300 a ton – which allows poor rice farmers to make some profit yet keeps rice affordable for poor rice consumers – we need to produce an additional 8–10 million tons of rice more than in the previous year for the next twenty years.”
Many countries do not have the capacity to grow enough rice on their own land to meet existing or anticipated demand. To meet their needs governments or the private sector import rice and some are exploring ways to invest in rice production or rice-growing land in other countries.
IRRI is not involved in any projects on land acquisition for rice production, nor does it provide advice on land acquisition, but it does find ways to help increase the overall rice supply – with a mandate to help poor rice farmers and consumers and improve environmental health.