Discovery of microworms in the Brazilian Federal District is the result of the first study on the diversity of this group of invertebrate fauna in the biome. Result shows that Cerrado biome is as rich in this type of fauna as the Amazon or the Atlantic Foresta. Smaller than earthworms, Enchytraeidae are also good indicators of soil quality and biodiversity. A research carried out in the Brazilian Federal District and Goiás state soils the reveals that the Cerrado biome is home to 20 potential new species and a new Enchytraeidae genus (Oligochaeta, Annelida), also known as microworms. They are organisms that occur in almost all soils in the world. The publication of these species and genus still depends on confirmation of some characteristics and more detailed analysis. The specimens were collected in natural vegetation and in agricultural areas. They belong to six different genera. This is the first quantitative and qualitative survey of the Enchytraeidae population in the Cerrado carried out with standardized methodology. It was also supported by the Research Support Foundation of the Federal District (FAP-DF). The surveys showed that the Cerrado is as rich in these organisms as forests in other Brazilian biomes with milder temperatures and higher rainfall. Embrapa Cerrados (DF) researcher, Cintia Niva, coordinator of the study, says the results are surprising: “The general idea was that there were few microworms in the Cerrado due to the prolonged drought period, since these invertebrates require moist soils to survive. However, the data obtained show that here we have a population as abundant and rich as that of the Atlantic Forest and that of the Amazon. Its population is made up of several possibly endemic species restricted to the Cerrado”. Microworms Enchytraeidae are close relatives of the well-known earthworms, but with a much smaller size and practically no pigmentation. Their internal organs can be seen when observed under a microscope. In the Cerrado, most of them are up to 1 cm long and 2 mm in body diameter. In the Atlantic Forest, specimens of up to 4 cm in length have already been found. It is important to study microworms due to the functions they play in the ecosystem. They contribute to the decomposition of organic matter, nutrient cycling, soil formation and the food chain. There are 710 species worldwide. Only 62 terrestrial or semi-aquatic species are known up to now in Latin America (47 of these exist in Brazil). The researcher says that there is a hypothesis that considers South America as the center of origin of microworms, which raises the expectation of a high diversity in that continent as more areas are studied. The data will serve as a basis for the use of this group of organisms as indicators of diversity conservation and soil quality as habitat in the Cerrado in different production systems. “There is still a lack of metrics that can assist in the diagnosis of soil quality, especially based on biodiversity. For this reason, the work with bioindicators is important to estimate the environment sustainability”, Niva explains. Demands of the United Nations (UN) Agenda 2030 Agenda for Sustainable Development include the need for sustainable production systems, protection of life on land and actions to combat climate change. In this scenario, productive systems must promote the reduction of biodiversity loss and guarantee the provision of ecosystem services. “For this to happen, it is essential to know the biodiversity that there is in the soil in order to develop useful tools for monitoring and add value to production systems”, the researcher adds. Indicators of soil quality The beings that inhabit the soil are responsible for keeping it in good functioning. However, they are not always given due attention. One may wonder why not study only earthworms as a reference for soil health. “Despite the fact that Enchytraeidae and earthworms contribute to the same ecosystem services, such as nutrient cycling and soil structure, they do it differently due to their body size and their position in the food chain,” Cintia Niva replies. Enchytraeidae also have different susceptibilities to soil quality and habitat, which is why they often occur in places where earthworms are not abundant. Therefore, the ecological relevance, its wide geographical distribution and sensitivity to changes in the environment make microworms potential candidates for systems monitoring. Native vegetation versus production areas The samples were collected from 2016 to 2018 in an area of natural vegetation in the National Park of Brasilia, the Botanical Garden of Brasilia and the Cerradão area at Embrapa Cerrados. In cultivated areas, they collected samples of soil from the following agrosystems: integrated crop-livestock-forestry system (ILPF); integrated crop-livestock system (ILP); silvopastoral system; eucalyptus crop; pastures and agroecological system. In general, it can be noticed that the density and quantity of microworms is higher in native vegetation soils, due to the greater availability and quality of organic material and the lower degree of anthropic activity in the soil. High densities are also found in cultivated areas, but with less species diversity. More than 85% of the Enchytraeidae found in cultivated areas belong to the genus Enchytraeus. "Previous research characterizes these species as r-strategists, that is, they reproduce quickly and adapt easily to altered environments, which explains their predominance in agricultural areas", Niva justifies. Agricultural activity modifies soil conditions as a habitat. It reduces the population of genera and species prevalent in areas of native vegetation, which are apparently more sensitive, as Guaranidrilus (the most abundant genus in natural areas). These conditions favor the increase in less sensitive populations, or more tolerant ones, and with ease of adaptation and reproduction. Appropriate methodology For this research, the collection and extraction of Enchytraeidae was carried out in accordance with the international protocol ISO 23611-3, the same as adopted in pioneering studies in the Amazon and the Atlantic Forest. The samples, soil columns with standardized size, were kept refrigerated. After the organisms were extracted using specific equipment, they were separated and analyzed in up to 2 days, since the taxonomic characteristics are more visible, under an optical microscope, in alive individuals. Subsequently, the specimens were fixed in liquid preservative. The taxonomer Rüdiger Maria Schmelz, from the University of Coruña (UDC), Spain, carries out the determination and confirmation of the species. In Brazil, there is no specialized taxonomist in this group. Several studies of the edaphic fauna carried out with other methods have demonstrated the presence of microworms in several both natural and cultivated ecosystems in South America, sometimes with significant population densities. These studies, however, did not determine their diversity, which makes it difficult to compare data and assess more accurately the efficiency of Enchytraeidae as bioindicators. The initial hypothesis was that there would be fewer microworms in tropical regions than in temperate ones. “Studies in the mixed Ombrophilous Forest in the state of Paraná report an average density of 12 thousand individuals per square meter and in the Amazon, less than 5 thousand. Contrary to the initial hypothesis, the research indicated that the density in the Cerrado biome is 13 thousand, on average, in the rainy season and, in some situations, we even found 30 thousand”, the researcher celebrates. Regardless of this, there was a great population decline up to 5 cm deep in periods of soil drought. “Probably, the survival of these beings during the drought period depends on some strategy that still needs to be investigated, such as quiescence [period of dormancy or hibernation] or migration to deeper layers of soil”, she supposes. According to Niva, moisture is an important factor for Enchytraeidae, as they breathe through the skin. The researcher reports that she observed a sharp decrease in the population in 2016, probably due to the extreme and prolonged drought that occurred that year. In regions with temperate climate, microworms are already used to assess the biological quality of soil in different systems, impacts related to deforestation, global warming, among others. The researcher says that they are also good laboratory-test organisms in and field tests to indicate the degree of soil contamination in relation to the toxicity of chemicals, heavy metals, petroleum products and even industrial and domestic waste. “At Embrapa, we have already tested the effect of soils with ash, rock powders and pesticides using Enchytraeidae in the laboratory. The expectation is that the Enchytraeidae may be used as bioindicators in the Cerrado biome”, Cintia Niva concludes