Bacteria may help frogs attract mates — ScienceDaily

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Brazilian scientists have discovered that the strong odors released by some amphibious species are produced by bacteria, and attracting spouses is one of their purposes. The bacteria in question are a noteworthy example of symbiosis as they contribute to the mating process of animals. An article describing the discovery of this role in microbes isolated from frog skin has been published in the journal Proceedings of the National Academy of Sciences (PNAS) .

"Frogs emit a pungent odor. Sometimes a particular species can be recognized by its odor, but until now, the function of this scent is unknown. It is usually considered a scent, meaning a Chemical warning signs, for example, repel predators in the case of skunks [ Mephitis mephitis ] in mammals," said Célio Haddad, professor at the Rio Claro Institute of Biological Sciences (IBRC-UNESP) at São Paulo State University, Brazil. . The co-author of this article.

According to Haddad, he is also a subsidiary of the Jaboticabal University Aquaculture Center (CAUNESP). This assumption is considered reasonable because many amphibians, especially when toxic, are brightly colored, which can be used as a visual alert. Frighten predators. “We think the smell may play a similar role in anurans [Frog and 蟾蜍],” he said.

This new study was based on a postdoctoral study by Argentine biologist Andrés Eduardo Brunetti, supervised by Professor Norberto Peporine Lopes. The study was conducted by the Ribeirão Preto Pharmaceutical College (FCFRP-USP) at the University of São Paulo and was supported by FAPESP.

"The importance and originality of Brunetti's research is that it shows for the first time that the odors emitted by heterosexual frogs are significantly different," Haddad said. “There is no other study on anurans that has described this behavior. The results show that this odor allows the male and female of the same species to recognize each other to achieve mating purposes.”

The study was also supported by the FAPESP Biodiversity Characterization, Conservation, Restoration and Sustainable Use Research Program (BIOTA-FAPESP) and the University of São Paulo (USP), the National Council for Scientific and Technological Development (CNPq). Coordination with higher education personnel in Brazil (CAPES).

"In anurans, you often see different species sharing lakes or swamps. In these places, there are 30 male frogs per female of the same species. The question is how females identify males of their own species. Many belong to several Men of all species are speaking at the same time," Brunetti said.

"As we all know, the function of anuran males is to attract women, and each species has a special song. Our research shows that the odor seems to play a similar role, acting as an olfactory signal, enabling women to recognize them. The male of his own species."

Biologists are also unaware of the difference in odor between male and female frogs. Brunetti found this difference in his research, the main purpose of which is to understand the chemical composition of the volatile constituents of various frog skins.

His work assumes that smell is a chemical warning sign that helps to defeat predators. To test this hypothesis, Brunetti conducted field investigations in several locations in São Paulo and Rio de Janeiro, collecting specimens of tree frogs Boana prasina .

"It is very difficult to collect females in the wild. Initially, we managed to collect only males. When we noticed that their odors seem to have gender differences, I once again entered the wild, with the specific purpose of capturing females. For comparison," he said .

"In the study of volatile compounds in two other frog species during the Ph.D. study at the Argentine Natural Science Museum in Buenos Aires, I found these secretions from 35 to 42 in 9 different chemical classes. Compound composition. Then we realized that some compounds have specific compound characteristics produced by bacteria."

Brunetti came to Brazil to investigate whether the selected tree frogs had skin bacteria that produced the characteristic odor of each species, and if so, which compounds they produced. His laboratory research was conducted in two ways: analyzing the volatile compounds released by the skin of these frogs and identifying the bacteria on the skin.

Brunetti and colleagues used gas chromatography and mass spectrometry to analyze the diversity of volatile constituents secreted by B skin. Prasina . They found that adult males and females secrete 60-80 compounds, including alcohols, aldehydes, olefins, ethers, ketones, methoxypyrazines, terpenes and thioethers.

Male and female compounds are identical, but the researchers were surprised to find significant differences in levels of methoxypyrazine, terpene and thioether.

"These three components are responsible for the differences between men and women. Thiol and methoxypyrazine are usually produced by microorganisms," Brunetti said.

They decided to determine in B whether microorganisms are the source of these compounds. Prasina . To this end, they isolated, cultured and identified the bacteria associated with the skin of these frogs and analyzed their volatile constituents.

No less than 128 different components were detected. Analysis of each component revealed that the four methoxypyrazines present in males and females were produced by a single bacterium Pseudomonas .

in B. Brunetti found that prasina women suffer from methoxypyrazine levels much higher than men. Two of the four types of methoxypyrazine were measured at higher levels in women, while two higher levels were found in males.

symbiotic relationship

About Pseudomonas sp. The interesting thing about is that these bacteria live on the skin of males and females, where they metabolize the same volatile compounds at different concentrations depending on the sex of the host. ," Brunetti said.

He added that the levels of methoxypyrazine measured in these frogs indicate a complex metabolic interaction mechanism that creates a different environment on the skin of men and women, favoring the characteristic methoxy groups of each sex. Synthesis of pyrazine.

"These frogs and bacteria have a symbiotic relationship. In exchange for the services provided by bacteria, sex differentiation through odors, frogs provide an environment – their own skin – bacteria can multiply on them," he explained.

The function of this gender difference in methoxypyrazine levels is unclear. “However, we believe that the difference in odor helps the male frog of the species identify females of the same species where other frog species inhabit,” Brunetti said.

"We know that many auras use visual communication [ Bright Skin ] to repel predators and voice exchanges [ vocalization ] to appeal to female partners. Perhaps B. Prasina uses a form of olfactory communication to achieve the same purpose."

Brunetti will try to confirm this hypothesis in future research. If it is correct, it will have a major impact. “Currently, only one anuran in Madagascar communicates through scent. In amphibians, baboons, they are ancient distant relatives, and this form of communication is known to be used,” Haddad said.

"If B.prasina uses scent as a form of communication, it is likely that other species also use olfactory communication because each species has a unique scent. Brunetti's discovery, if confirmed , opened up a new field of reptilian research, and now will focus on the olfactory communication between the anus, not just visual and acoustic communication."

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