Células do “heart” Bees may mask pesticide effects on insects

Células do “heart” Bees may mask pesticide effects on insects

Elton Alisson | Agency FAPESP 19/05/2015 – The indiscriminate use of pesticides in crops and the disposal of toxicants – such as trace metals in low concentrations – in the soil and air, as well as rivers and lakes, They are seen as some of the factors responsible for the decline of populations and the disappearance of bee species currently observed in different parts of the world.

The real effects of these chemicals on insects, Yet, They are not very well informed, since studies conducted in recent years in Brazil and other countries to diagnose whether exposure of bees to varying concentrations of certain types of pesticides alter the mortality and survival, beyond the behavior and internal organs of the animal - like the brain -, They did not identify significant changes.

"Sometimes, It is not because they are observed changes in mortality and behavior, in addition to specific internal organs that can be impacted by a particular pesticide, that the product is not causing effects on bees ", said Fabio Camargo Abdalla, professor in the Department of Biology at the Federal University of São Carlos (UFSCar), at Agency FAPESP.

The researcher and student Caio Eduardo da Costa Domingues - who holds a master's degree in the Graduate Program in Biotechnology and Environmental Monitoring at UFSCar in Sorocaba with Bag FAPESP - identified that bees of the genusBombus - popularly known as bumblebees or mamamgabas - have an integrated cellular system capable of “compensating” for the effects of toxicants and, to fight them, "Mask" their real impact until a certain concentration and exposure time.

The discovery - research result "Cadmium Action and the original Roundup® on internal organs of Bombus morio and Bombus atratus (Hymenoptera: Bombini), supported by FAPESP - was reported in an article published in the journal PloS One.

The results will be presented at the next Latin American Congress of Environmental Toxicology and Chemistry Society (Setec, its acronym in English), expected to occur between days 7 is 10 of September, em Buenos Aires, na Argentina.

"The effects of exposure of bees to a given xenobiotic [synthetic chemicals that do not occur naturally in the environment, as pesticides and trace metals] can be compensated for this integrated cellular system, Call hepatonefrocítico ", said Abdalla.

According to the researcher, hepatonefrocítico the system identified by microcospia the carpenter bees is composed of cells that make up the so-called insect fat body - that have homologous function to the liver, human -, plus pericardial cells and cells of the immune system (Hemocyte) do animal.

This set of cells and tissues is located and willing, no accident, layered in a contractile region (myogenic) around the dorsal vessel (the heart) Bees - a blind bottom tube extending into the abdomen and opens the insect's head start - and it works, in a coordinated manner, as a filter for blood (hemolinfa) Bees.

When bees are exposed to xenobiotics, the fat body cells are the first to be activated and represent the first barrier against chemical aggression.

If the body's fat cells can not stop the "attack" of the chemical and are affected or destroyed, pericardial cells are called.

However, cellular immune response occurs throughout the process of "combat", revealed by morphology and blood cell counts throughout the period of exposure to pesticides and trace metals.

Toxic substances neutralized by pericardial cells are released back into the hemolymph and can be filtered by tubule Malpighian - insect excretory organ.

Immune cells Bees, in turn, participate during the entire process, He explained Abdalla.

"This association of cells, along with the tubule Malpighian, bees operates in a manner analogous to the kidney and liver of humans and represent the front line of the insect to compensate for the deleterious effects of exposure to chemicals ", said.

Potential biomarker

In order to evaluate what the compensation limit of the effects of toxicants by hepatonefrocítico system of bees, the researchers performed experiments that exposed carpenter bees (Praetorian morio) the cadmium doses considered safe for Class I and II waters by the National Environmental Council (CONAMA), besides sublethal doses of Thiamethoxam - the pesticides most commonly used in Brazil - and glyphosate for varying periods.

The results of the cellular response analysis of the insects - performed by the system hepatonefrocítico cell count in the hemolymph - revealed that exposure for two days to one part per billion (ppb) Cadmium, diluted in 2 milliliters (ml) of water, It caused the cell death of the fat body and an intense activity of pericardial cells, causing the system to collapse and destruction of the dorsal vessel of animals.

“We are observing that this also occurs with different species of bees that not only Praetorian morio, as also Praetorian atratus, Apis mellifera is on Xylocopa suspect, that shares the same niche with Bombus, with the difference that it is a solitary bee, and not social ', He explained.

"That is why, hepatonefrocítico this system can be used as a biomarker to assess the morphological level of environmental stress on bees ", indicated.

According to researcher, Simple activation of the cells that make up this system by the bees when exposed to a particular type of xenobiotic is already an indication of the detrimental effect of the chemical substance, once the insect would be deviating metabolically energy that could be used for other functions, as the collection activity, to do all this physiological system work.

"This could harm a colony extrapolated this energy diversion effect for all kinds of foraging bees exposed in the field", said Abdalla.

The system can also predict hepatonefrocítico, quite accurately, which insect organs can be affected by a particular toxicant agent to assess what types of cells are being more damaged in the system, since they have different functions associated with other organs, He pointed out the researcher.

Beyond detoxification and filtration, the hepatonefrocítico system cells are involved in ovarian development, forming and maintaining cuticle that covers the body of the bee (cuticulogênese), with regulating hormones from the brain of insects glands, He explained.

"This system could be used as a checkpoint. By studying the conventional methods the effect of a given insecticide neonitocinoide - which is extremely harmful to the nervous system cells of bees - in the insect, morphological changes that can not be perceived in the brain or mortality and survival of the animal. But you can check if that detoxification and filtering system is activated ", pointed.

The researchers plan future analysis by gas chromatography techniques and mass cells of the fat body spectrometry and pericardial comprising the hepatonefrocítico system of bees to study the dynamics of metabolism of xenobiotics by insects.

In the example of what happens in the human liver, I agrochemicals, for example, They are "broken" by the metabolic system of bees into smaller molecules, calls seconds metabolites.

In certain cases, those seconds metabolites are much more potent and harmful to the insect's body than the original agrochemical molecule, said Adballa.

"It happens to the Thiamethoxam, which is an agrochemical intensively studied in our laboratory and, when ingested, potential toxicant can increase up to 300 more times ", said.

O artigo “Hepato-nephrocitic system: a novel model of biomarkers for analysis of the ecology of stress in environmental biomonitoring” (doi: 10.1371/journal.pone.0132349), from Abdalla and Domingues, can be read in the magazine PLoS One in www.plosone.org/article/related/info:doi/10.1371/journal.pone.0132349.