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B IOPHYSICS

Monitoring bees

Microsensors help scientists understand the behavior of Apis mellifera exposed to pesticides and climate change

Drone of an Africanized Apis mellifera with microsensor attached to its thorax

VALE/CSIRODrone of an Africanized Apis mellifera with microsensor attached to its thoraxVALE/CSIRO

The bee population is experiencing a significant decline in several countries, including Brazil. In August 2013, TIME Magazine ran a cover story on the threat posed by the disappearance of honeybees, entitled “A world without bees: The price we’ll pay if we don’t figure out what’s killing the honeybee.” The disappearance of these honey producers is worrisome not only for its threat to the existence of that product, but also because bees have drawn particular attention to the key role they play in food production. And with good reason. Honeybees are responsible for pollinating 70% of all plants consumed on Earth, because they transport pollen from one flower to another, fertilizing them in the process. Some crops, such as almonds produced and exported around the world by the United States, rely exclusively on these insects for pollination and fruit production. Apples, melons and Brazil nuts, to cite just a few examples, are also dependent on pollinators.

Among the probable causes for the bees’ disappearance are the chemical compounds present in neonicotinoids, a class of pesticides widely used throughout the world. In addition to pesticides, other factors such as climate change involving a greater number of extreme events, infestation by a mite that feeds on the hemolymph of bees (which corresponds to blood in invertebrates), monocultures such as corn and wheat that provide little pollen, and even techniques for increasing honey production, may be responsible for the phenomenon known as colony collapse disorder (CDC), which causes the insects to become spatially disoriented and die outside the hive. The disorder has already caused the death of 35% of bees raised in captivity in the United States.

Abelhas_IMG_20121219_111600-2VALE/CSIROSeeking answers to help combat the problem, the Vale Technology Institute (ITV) in Belém, in the state of Pará, has collaborated with the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia to develop microsensors—tiny squares measuring 2.5 millimeters on a side and weighing 5.4 milligrams—that are attached to the thorax of Africanized Apis mellifera bees (stinging bees that are a hybrid of European and African varieties), to analyze their behavior under the effect of pesticides and climatic events. One part of the experiment is being conducted in Australia, and the other part in Brazil.

In the Australian state of Tasmania, an island south of the continent of Oceania, a comparative study will be carried out using 10,000 bees to analyze how they react when exposed to pesticides. For this purpose, two hives were placed in contact with contaminated pollen, and two others were not. “If there is any noticeable change in the behavior of the insects exposed to the pesticide, such as inability to fly back to the hive, disorientation or even early death, the product will become the main suspect for colony collapse disorder,” says physicist Paulo de Souza, coordinator of the research and a visiting professor at ITV. The project was begun in September 2013 and is expected to conclude in April 2015; the findings are to be released in the second half of that year. “The main reason for choosing Tasmania is that it has a distinct environment where there is no pollution, and half the territory consists of forests,” says Souza, who is also a professor at the University of Tasmania.

Size of microsensor compared to R$1 coin

WILLIAN ABREU/VALESize of microsensor compared to R$1 coinWILLIAN ABREU/VALE

Australian honeybees weigh about 105 milligrams, so the sensor represents about 5% of their weight. Bees of the same species in Brazil weigh about 70 milligrams, which led the researchers to conduct tests in wind tunnels to determine whether the sensor could affect their ability to fly. “We studied the wing beats and body angle of bees with and without the sensor, and confirmed that there was no change in their ability to fly,” Souza says.

The part of the experiment being conducted in Brazil is focusing initially on monitoring 400 bees for three months to assess the extent to which climate change—particularly changes in rainfall patterns in Amazonia—affect the insects. “We don’t know how they will behave with the projected increase in temperature and the climate change expected to be triggered by global warming,” Souza says. The studies are being conducted at an apiary in the municipality of Santa Bárbara do Pará, near Belém.

“Each sensor has an engraved code that serves as an identifier for every bee,” Souza says. The sensor will enable the scientists to analyze details about every individual in the hive. Once this phase of the research is completed, a second study will begin, this time with native stingless bees from Pará, which appear to be more severely affected by climate change than European bees. Although they do not produce honey in great quantity, they are excellent pollinators. Since the bees have a relatively short life cycle—about two months—several generations can be monitored.

Physicist Paulo de Souza checks a hive in Pará

VALE/CSIROPhysicist Paulo de Souza checks a hive in ParáVALE/CSIRO

The sensors being tested in the field belong to a first generation developed by ITV and CSIRO—and others are in the pipeline. “One innovation we’ve come up with is that we’ve been able to achieve a communication distance of up to 30 centimeters,” the researcher notes. This was done by improving the quality of the chip’s antenna, which enabled it to communicate over longer distances. “CSIRO developed a wi-fi system and did the antenna modification.” During his doctoral studies, Souza worked with a research group whose focus was to build sensors for space missions, like those installed on the mechanical arm of the rover Opportunity sent to Mars in 2004. That geological exploration mission to the Red Planet is still ongoing as it searches for past signs of water.

The microsensor consists of a chip that holds 500 Kb of memory—enough to keep second-by-second data for nearly a week, an antenna and a battery. The information on the bees’ movement captured by the chip is relayed to antennas set up around the hive and at feeding stations, and then transferred to a control center. Using the data collected in the field, the researchers construct a three-dimensional model of the insects’ movement, enabling them to see whether the bees are acting normally, or if they are disoriented for some reason and unable to return to their original location.

Each antenna costs about $300, which makes the technique more practicable compared to similar devices costing around $10,000. “The chip itself, which runs about $.30, is much cheaper than the ones on the market, which sell for $6.” The physicist points out that from the outset they have looked for a manufacturing process that will facilitate industrial-scale production at the lowest possible cost.

The next generation of chips, which is in the final development stage, will be able to manage and store their own energy and also capture the temperature, humidity and amount of solar radiation in the environment. And the plans don’t end there. “Within four years we want to develop a chip the size of a grain of sand to monitor mosquitoes that transmit dengue and malaria,” Souza says. Among the various strategies studied for implementing this tiny device, the most promising, in his opinion, is jet-spraying it onto the insects.  

070-073_Abelhas _221Another goal of the project is to expand the sensors’ radius of operation. “We want to increase it to hundreds of meters to explore this technology platform in other future applications, such as aircraft fuselages, clothing for workers in high-risk areas and eyeglasses that monitor ultraviolet exposure,” he notes. The two institutions have allocated $25 million over a five-year period for the project, which will involve 23 researchers from several fields of knowledge.

Pesticides and bees
Bee behavior is also the focus of several studies being conducted by a group of 20 researchers under the coordination of Professor Osmar Malaspina of the Institute of Biosciences at São Paulo State University (Unesp) in Rio Claro. Malaspina’s colleagues in the research group are Professors Roberta Nocelli and Elaine Cristina da Silva Zacarin, both from the Federal University of São Carlos (UFSCar), and Professor Stephan Malfitano de Carvalho of the Federal University of Uberlândia (UFU).

“We are the first research group in Brazil to study the relationship between pesticides and bees,” Malaspina comments. He has done research on the topic since his master’s program in the 1970s, but it was not until 2000 that he actively pursued the subject again as a result of beekeepers’ claims that they were losing bees following aerial insecticide spraying, mainly to combat sugarcane pests. “The reports of losses started coming in after new products were introduced on the market,” he explains.

According to Malaspina, 20,000 bee colonies were lost in the state of São Paulo between 2008 and 2010; 100,000 in the state of Santa Catarina in 2011 alone; and estimates point to annual losses of 40% of the hives in the states of Rio Grande do Sul and Minas Gerais. Each colony or hive contains 50,000 individuals on average. “The information on the losses was reported by beekeepers, but we don’t know the cause of death, because bees can die from a number of factors other than insecticides, such as disease, handling, extreme drought, and other variables.” In some cases, such as that of a beekeeper in the municipality of Boa Esperança do Sul, in São Paulo State, a cause-and-effect relationship has been proven. “On a Tuesday in 2008 he had 400 hives, on Wednesday there was aerial spraying nearby, and on Thursday, the very next day, all the bees were dead,” says Malaspina. The results of an analysis indicated a neonicotinoid insecticide as the cause of the deaths.

One of his group’s studies to evaluate the effect of pesticides on bee organs is being carried out in the laboratory and in incubators that simulate hive conditions. Results of tests performed by the researchers indicate that the pesticides affect the bees’ digestive system and brain. In the more serious cases they are unable to feed, and die of starvation. Other experiments are being conducted to determine how these insects are affected when they do manage to survive poisoning. This knowledge is important for protecting the enormous variety of bees currently found in Brazil, which number about 2,000 described species.

In addition to concern over beekeepers’ losses, there is a risk to crops that rely on bees for pollination. Passion fruit, for example, is only produced if it is visited by bumblebees. This is also true in the case of eggplant, sweet pepper and other plant species whose closed flowers require specific pollinators.

Projects
1.
Interaction between pesticides and Nosema infection in Africanized Apis mellifera: biological effects and detection of cellular biomarkers (nº 2013/09419-4); Grant mechanism Regular Line of Research Project Award; Principal investigator Elaine Cristina da Silva Zacarin (UFSCar); Investment R$199,981.70 (FAPESP).
2. Evaluation of the adverse effects of exposure to pesticides and pathogens in bees: study of cellular biomarkers in target organs (nº 2008/51473-8); Grant mechanism Regular Line of Research Project Award; Principal investigator Elaine Cristina da Silva Zacarin (UFSCar); Investment R$99,150.00 (FAPESP).

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