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Tag Archive for: integrated pest management

What a mosquito’s immune system can tell us about fighting malaria

What a mosquito’s immune system can tell us about fighting malaria

Immune cells in a malaria-transmitting mosquito sense the invading parasites and deploy an army of tiny messengers in response. These couriers help turn on a mosquito’s defenses, killing off the parasites, a new study suggests.

This more detailed understanding of the mosquito immune system, published January 20 in Science Immunology, might help scientists design new ways to combat malaria, which infects more than 200 million people per year.

“If we understand how the mosquito reduces the parasite to begin with, we hope we can boost these mechanisms to completely eliminate these parasites [in mosquitoes],” says Kristin Michel, an insect immunologist at Kansas State University in Manhattan who wasn’t part of the study.

Different parasites in the Plasmodium genus cause malaria. The disease is spread by certain Anopheles mosquitoes. These mosquitoes have natural defenses against Plasmodium that keep them from being overrun with the parasites when feeding on an infected person’s blood. But malaria transmission still occurs, because some Plasmodium species are particularly skilled at evading mosquito immune systems.

Previous research has shown that hemocytes, the insect equivalent of white blood cells, help mosquitoes fight off pathogens. Carolina Barillas-Mury and her colleagues at the National Institute of Allergy and Infectious Diseases in Rockville, Md., injected Anopheles gambiae mosquitoes — a primary spreader of malaria in sub-Saharan Africa — with a dye that stained their hemocytes. Those mosquitoes snacked on mice infected with a rodent version of malaria. Then the scientists watched the dyed hemocytes’ response.
Parasite’s problem

Sensing the presence of a malaria-causing parasite, mosquito immune cells (teal) kill themselves and release microvesicles (red) that activate cellular machinery that fights off the parasites, a new study finds.

Hemocytes that detected certain chemical fingerprints left by the parasites began to self-destruct. These dying hemocytes released plumes of tiny vesicles that then activated the mosquito’s defenses against the parasite, the researchers found. The vesicles triggered a protein called TEP1 to take down the parasite. Scientists already knew that TEP1 is an important part of mosquitoes’ immune response against Plasmodium parasites, but it wasn’t clear how the protein was called into action. Without the vesicles, TEP1 didn’t target the parasites.

Barillas-Mury and colleagues don’t know exactly what the microvesicles contain. But she suspects they carry messenger molecules that jump-start TEP1 and other proteins involved in this immune response.

This type of response “is a very powerful defense system because it can make holes in the parasite and kill it,” says Barillas-Mury. “You want it to be active, but in the right place and at the right time.” Plasmodium parasites set up shop in different places in the mosquito gut depending on their life stage. Microvesicles, much smaller than the hemocytes, can more easily move through different gut compartments to trigger a localized immune response right where the parasite is.

The researchers eventually hope to use their understanding of the mosquito immune response to develop new ways to stop malaria. They’re interested in creating a vaccine that prevents mosquitoes that bite an infected person from passing along the parasite. Such a vaccine could be used in combination with others under development that would prevent people infected with the parasite from becoming sick, Barillas-Mury says.

Source: Sciencenews.org

Ants communicate by mouth-to-mouth fluid exchange

Ants communicate by mouth-to-mouth fluid exchange

The study from the University of Lausanne, Switzerland, suggests Florida carpenter ants can collectively influence their communities by shifting the cocktail of proteins, hormones and other small molecules that they pass mouth-to-mouth to one another and their young through a process called trophallaxis.

“Food is passed to every adult and developing ant by trophallaxis. This creates a network of interactions linking every member of the colony,” says senior author Laurent Keller, Professor in the Department of Ecology and Evolution.

“A lot of researchers consider trophallaxis only as a means of food-sharing,” adds Professor Richard Benton of the Center for Integrative Genomics, also a senior author of the study. “But trophallaxis occurs in other contexts, such as when an ant is reunited with a nest-mate after isolation. We therefore wanted to see if the fluid exchanged by trophallaxis contains molecules that allow ants to pass other chemical messages to each other, and not just food.”

To answer this question, the team, led by first author and postdoctoral researcher Dr Adria LeBoeuf, analysed fluid from pairs of ants engaged in trophallaxis. Surprisingly, they identified a large number of proteins that appear to be involved in regulating the growth of ants, along with high levels of juvenile hormone, an important regulator of insect development, reproduction, and behaviour.

To see what effect this hormone has on the growth of larvae fed by trophallaxis, the scientists added it to the food of larvae-rearing ants and discovered that the hormone made it twice as likely that the larvae would survive to reach adulthood.

“This indicates that juvenile hormone and other molecules transferred mouth-to-mouth over this social network could be used by the ants to collectively decide how their colony develops,” says LeBoeuf. “So, when the ants feed their larvae, they aren’t just feeding them food, they are casting quantitative ballots for their colony, administering different amounts of growth-promoting components to influence the next generation.

“The effects of juvenile hormone that we see are consistent with previous studies in other ants and in bees where larvae treated with an analogue of this hormone tend to develop into larger workers and even queens.”

Along with growth proteins and juvenile hormone, the team also identified small molecules and chemical signals in the carpenter ants’ trophallactic liquid that help them recognize their nest-mates. They demonstrated for the first time the presence of chemical cues in the fluid that are known to be important in providing ants with a colony-specific odour that allows them to distinguish family from non-family members.

“Overall, we show that liquid transmitted among ants contains much more than food and digestive enzymes,” adds LeBoeuf. “Our findings suggest that trophallaxis underlies a private communication channel that ants use to direct the development of their young, similar to milk in mammals.”

“More generally, this opens the possibility that the oral exchange of fluids, such as saliva, in other animals might also serve previously unsuspected roles.”

Source : ScienceDaily

Common insecticides are riskier than thought to predatory insects

Common insecticides are riskier than thought to predatory insects

Neonicotinoids — the most widely used class of insecticides — significantly reduce populations of predatory insects when used as seed coatings, according to researchers at Penn State. The team’s research challenges the previously held belief that neonicotinoid seed coatings have little to no effect on predatory insect populations. In fact, the work suggests that neonicotinoids reduce populations of insect predators as much as broadcast applications of commonly used pyrethroid insecticides.

“Predatory insects contribute billions of dollars a year to agriculture through the elimination of crop pest insects,” said Margaret Douglas, postdoctoral researcher in entomology, Penn State. “We have found that neonicotinoid seed coatings reduce populations of these natural enemies 10 to 20 percent.”

According to John Tooker, associate professor of entomology, Penn State, the use of neonicotinoids has risen dramatically in recent years, especially for large-acreage crop species like corn, soybeans and cotton. The insecticide is most often applied to seeds as a prophylactic coating. When the seeds are planted, the insecticide enters the soil where some of it is taken up by plant roots. The chemical then runs systemically through the plant, protecting young seedlings from insect pests.

“Applying insecticides to seeds rather than broadcasting them across a field was thought to reduce unwanted effects on natural enemies,” said Douglas. “But we found that seeds treated with neonicotinoid insecticides reduced populations of natural enemies by 10 to 20 percent in North American and European farming systems. Surprisingly, this effect was about the same as that associated with broadcast applications of pyrethroids.”

The team’s research appeared in the online journal PeerJ.

The team used a statistical method, called meta-analysis, to combine the results of more than 1,000 observations from 20 field studies across North America and Europe that tested the effects of seed-applied neonicotinoids on predatory insects. “Unfortunately, the available literature is difficult to interpret,” said Tooker. “Some studies show little influence of neonicotinoids presented as seed treatments on arthropod predators that are common in crop fields, whereas others show a strong influence of these seed treatments. By using a meta-analysis approach, we were able to combine the results of many studies to quantitatively reveal the overall influence of neonicotinoids on predator populations.”

Not only did the researchers find that neonicotinoid seed coatings significantly reduced natural enemy populations, they also found that the insecticide acted more strongly on insect predators than on spiders. In other words, spiders appeared to be less susceptible to neonicotinoids than insects, which is consistent with previous research.

“This result suggests that neonicotinoids are reducing populations of natural enemies at least partly through their toxic effects rather than simply by reducing the availability of their crop pest foods,” said Douglas. “After all, insects are more susceptible to these toxins than spiders, whereas the two groups should be similarly affected by a lack of food.” The researchers note that their results may help farmers and pest management professionals better weigh the costs and benefits of neonicotinoid seed treatments versus alternatives.

“Several governments have restricted the use of neonicotinoids out of concern for their possible effects on pollinators,” said Douglas. “But this raises the questions, ‘What will farmers do without these products? If they switch to broadcast applications of pyrethroids, will those products be better or worse for predatory insects?’ While our results do not speak to the pollinator issue, they do suggest that predatory insects are affected similarly by seed-applied neonicotinoids and broadcast pyrethroids.”

The answer to the problem, noted Tooker, lies in the application of integrated pest management (IPM), a strategy that uses a combination of techniques — which may or may not include the targeted use of insecticides — to control pests, rather than universally deploying prophylactic tactics like insecticidal seed coatings.

“Substantial research exists supporting the value of IPM for pest control,” he said. “It is the best chance we have of conserving beneficial insect species while maintaining productivity in our agricultural systems.”

Source: Science Daily

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