University of São Paulo: Guards form “sanitary barrier” and prevent jataí bees with fungus from entering nests

The jataí bee ( Tetragonisca angustula ) is a stingless, docile and easy-to-handle species, but curiously has a sophisticated recognition system, to the point of aggressively preventing the entry into the nest of companions exposed to fungi that can contaminate the colony. . The discovery took place in research carried out by the Luiz de Queiroz Higher School of Agriculture (Esalq) at USP, described in an article published in the scientific journal Chemosphere . The researchers found that jataí guards, which control access to the nests, recognize chemical changes in the bodies of bees that have had contact in the field with the fungus Beauveria bassiana , used as a biopesticide, preventing its entry.

Jataí has ​​a wide distribution in Latin America, especially in Brazil. “It is an important pollinator bee, not only of agricultural crops, but also of several species of wild plants”, points out researcher Denise Alves, who is carrying out post-doctoral studies at Esalq, one of the authors of the article. “In addition to the ecological role, due to pollination, there are many jataí breeders, largely due to the honey produced, which makes the species of high socioeconomic importance in Brazil.”

“Stingless bees, a group with more than 250 species in Brazil, represent a resource of increasing use for pollination of crops in tropical regions. Annually, agricultural pollination contributes with an estimated economic value of 12 billion dollars in the country”, highlights the researcher. “As bees forage for food in the field, they are exposed to pesticides applied to agricultural crops, whether chemical or biological, and we still know very little about their effects on these insects.”

The researchers carried out experiments that involved behavioral observations and chemical analyses, focusing on the recognition of nestmates by jataí guards. “The guards are 30% larger bees and have longer antennae than the other workers”, reports Denise. “It is already known that guards control the entry of forage bees, that is, those that go to the field, preventing the entry of those that do not belong to the nest.”

The study showed that the fungus Beauveria bassiana modifies the chemical profile of the cuticle that covers the bodies of bees. “The guards have a kind of ‘mold’ for the odors of their companions in their nest and, when there is any change in the chemical composition of the cuticle of these bees, they detect this difference and prevent their entry”, emphasizes the researcher. “Thus, the guards act as a ‘sanitary barrier’, preventing bees with spores of the fungus from entering their nests and that fungus from spreading and infecting the other bees.”

“Although contaminated bees no longer enter the nest, it is better to lose some mates than to risk an outbreak caused by the fungus in the colonies”, says Denise. “Until now, there have been no studies on the behavior of stingless bees against fungi used as biopesticides in agriculture, but only assessments that consider the mortality rate of these bees.”

The researcher says that a similar study was carried out in Italy, but analyzing stinging bees ( Apis mellifera ). “The research showed that, in this case, the guards of this species accept bees exposed to the fungus, which increases the chances of transmission of the pathogen between colonies”, she points out. “In jataí, considering that guards are larger and have longer antennae, our hypothesis was that they would be able to detect and recognize contaminated nestmates, unlike what happened in Apis mellifera. ”

According to Denise, due to the increasing use of biopesticides in agricultural crops, ecotoxicological assessments of these products must go beyond mortality rates. “It is also necessary to evaluate their effects on the behavioral and physiological characteristics of bees, which are nature’s main pollinators, and stingless bees are suitable for this evaluation due to the diversity of species and their increasingly frequent use in crop pollination. ” The research was carried out during Felipe Chagas Rocha Almeida’s master’s degree, supervised by Professor José Maurício Simões Bento, from the Chemical Ecology and Insect Behavior Laboratory of the Department of Entomology and Acarology at Esalq.

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