Dynamics of major environmental disasters involving fire in the Brazilian Pantanal.

The 2020 environmental catastrophe in Pantanal has highlighted the fragility of environmental policies and practices for managing and fighting fires in this biome. Therefore, it is essential to know the causes and circumstances that potentiate these fires. This study aimed to: (I) assess the relationship between fire foci and carbon absorption (GPP), precipitation, and carbon dioxide (CO2) flux; (ii) analyze vegetation recovery using the differenced normalized burn ratio (ΔNBR) in Brazilian Pantanal between 2001 and 2022; and (iii) identify priority areas, where the highest intensities of fire foci have occurred, in order to guide public policies in Brazil to maintain local conservation. To this purpose, fire foci were detected using data from the MODIS MOD14/MYD14 algorithm, annual precipitation with CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data), and CO2 flux using the MODIS/MODO9A1 product, and Gross Primary Production (GPP) with the MODIS/MOD17A2 product. The severity of the burned area was also assessed using the ΔNBR index and the risk areas were determined using the averages of these images. During the time series studied, a total of 300,127 fire foci were detected throughout the Pantanal, where 2020 had the highest number of foci and the lowest accumulated precipitation. The years with the highest precipitation were 2014 and 2018. The year 2018 was also the second year with the highest GPP value. The Pettit test showed a trend for 2008 and 2011 as the points of change in the CO2 flux and GPP variables. Principal component analysis clustered fire foci and precipitation on opposite sides, as well as GPP and CO2 flux, while ΔNBR clustered HS, MHS and MLS classes with the years 2020, 2019, 2002 and 2021. There was a high negative correlation between fire foci × rainfall and GPP × CO2 flux. The years with the largest areas of High severity (HS), Moderate-high severity (MHS) and Moderate-low severity (MLS) classes were 2020 and 2019, respectively. The most vulnerable areas for severe fires were the municipalities of Cáceres, Poconé, and Corumbá. The major fire catastrophe in 2020 is correlated with the low precipitation in 2019, the high precipitation in 2018, and the increased GPP, as well government policies unfavorable to the environment.

Effect of land uses and land cover on soil attributes in the southern Brazilian Amazon.

The growth of the world population has led to the expansion of agricultural areas to produce food that meets world demand, making it necessary to increase productivity and maintain environmental sustainability in these areas. Seeking sustainable food production, the agricultural use of soil must be assessed in view of optimal use or land as natural resource, as well as minimize the effects of global warming related to land use and land cover (LULC). We hypothesize that different LULC affects Amazonian soil attributes. In this study, the effect of different LULC in the southern Brazilian Amazon, namely, native forest, pasture, and rice and soybean crops, on the spatial variability of soil fertility and texture was assessed, seeking to obtain information that will guide farmers in the near future to better exploit their areas and contribute to a more sustainable agriculture. Descriptive statistical analysis was performed for the pH, H + Al, Al, Ca, Mg, P, K, Cu, Fe, Mn, Zn, V, m, organic matter, clay, silt, and sand values from soil samples under different LULC. To verify the data normality, the Shapiro-Wilk test at 5% significance was performed. Outlier analysis using boxplot graphics, principal component analysis (PCA), and cluster analysis was performed. Data were submitted to geostatistical analysis to verify the spatial dependence degree of the variables through semivariograms for interpolated kriging maps. Except for silt, all variables were well represented in the factor map. PCA revealed that the data variability can be explained mainly by pH, V, Ca, K, and Zn values, which are inversely proportional to m, P, and sand. Through geostatistical analysis, spatial dependence ranging from moderate to strong was observed, generating reliability in the prediction of most attributes in pasture, rice, and soybean areas. Yet, a spatial dependence ranging from moderate to strong was found, generating reliability in the prediction of most attributes in pasture, rice, and soybean areas. Our findings reveal a lower fertility and higher acidity in forest areas, whereas crop areas presented the opposite result.

Twenty-year impact of fire foci and its relationship with climate variables in Brazilian regions.

In recent years, Brazil has become a major global contributor to the occurrence of national fires and greenhouse gas emissions. Therefore, this study aimed to evaluate the fire foci data of the past 20 years to determine their relationship with climatic variables in various Brazilian regions. The variables evaluated included fire foci, land surface temperature, rainfall, and standardized precipitation index, which were obtained via remote sensing from 2000 to 2019. The data were subjected to trend analyses (Mann-Kendall and Pettitt tests) and a multivariate analysis of canonical variables for evaluation. The results showed that the Midwest and North regions had the highest occurrence of fire foci throughout the study period, and that the North region had the highest accumulated annual rainfall. Thus, these regions require specific public policies to prevent future fires. Overall, the Midwest, Southeast, and South regions exhibit significant increasing fire foci tendencies. Our results reveal that this trend is related to the El Niño-Southern Oscillation (ENSO) phenomena, which alter climatic variables such as precipitation, land surface temperature, and the standardized precipitation index. Finally, the sugarcane growing area had a significant linear relationship with fire foci in the Southeast region, especially in the state of São Paulo, the major national sugarcane producer.

Advance of soy commodity in the southern Amazonia with deforestation via PRODES and ImazonGeo: a moratorium-based approach.

The guidance on decision-making regarding deforestation in Amazonia has been efficient as a result of monitoring programs using remote sensing techniques. Thus, the objective of this study was to identify the expansion of soybean farming in disagreement with the Soy Moratorium (SoyM) in the Amazonia biome of Mato Grosso from 2008 to 2019. Deforestation data provided by two Amazonia monitoring programs were used: PRODES (Program for Calculating Deforestation in Amazonia) and ImazonGeo (Geoinformation Program on Amazonia). For the identification of soybean areas, the Perpendicular Crop Enhancement Index (PCEI) spectral model was calculated using a cloud platform. To verify areas (polygons) of largest converted forest-soybean occurrences, the Kernel Density (KD) estimator was applied. Mann-Kendall and Pettitt tests were used to identify trends over the time series. Our findings reveal that 1,387,288 ha were deforested from August 2008 to October 2019 according to PRODES data, of which 108,411 ha (7.81%) were converted into soybean. The ImazonGeo data showed 729,204 hectares deforested and 46,182 hectares (6.33%) converted into soybean areas. Based on the deforestation polygons of the two databases, the KD estimator indicated that the municipalities of Feliz Natal, Tabaporã, Nova Ubiratã, and União do Sul presented higher occurrences of soybean fields in disagreement with the SoyM. The results indicate that the PRODES system presents higher data variability and means statistically superior to ImazonGeo.

Application of remote sensing in environmental impact assessment: a case study of dam rupture in Brumadinho, Minas Gerais, Brazil.

The collapse of mining tailing dams in Brumadinho, Minas Gerais, Brazil, that occurred in 2019 was one of the worst environmental and social disasters witnessed in the country. In this sense, monitoring any impacted areas both before and after the disaster is crucial to understand the actual scenario and problems of disaster management and environmental impact assessment. In order to find answers to that problem, the aim of this study was to identify and analyze the spatiality of the impacted area by rupture of the tailing dam of the Córrego do Feijão mine in Brumadinho, Minas Gerais, by using orbital remote sensing. Land use and land occupation, phytoplankton chlorophyll-a, water turbidity, total suspended solids on water, and carbon sequestration efficiency by vegetation (CO2Flux) were estimated by orbital imagery from the Landsat-8/OLI and MSI/Sentinel-2 sensors in order to assess the environmental impacts generated by the disaster. Data were extracted from spectral models in which the variables that best demonstrated the land use variation over the years were sought. Mean comparison by t-test was performed to compare the time series analyzed, that is, before and after the disaster. Through the analysis of water quality, it was observed that the environmental impact was calamitous to natural resources, especially water from Córrego do Feijão.

Persistent fire foci in all biomes undermine the Paris Agreement in Brazil.

Brazil is one of the world's biggest emitters of greenhouse gases (GHGs). Fire foci across the country contributes to these emissions and compromises emission reduction targets pledged by Brazil under the Paris Agreement. In this paper, we quantify fire foci, burned areas, and carbon emissions in all Brazilian biomes (i.e., Amazon, Cerrado, Caatinga, Atlantic Forest, Pantanal and Pampa). We analyzed these variables using cluster analysis and non-parametric statistics to predict carbon and CO2 emissions for the next decade. Our results showed no increase in the number of fire foci and carbon emissions for the evaluated time series, whereby the highest emissions occur and will persist in the Amazon and Cerrado biomes. The Atlantic Forest, Pantanal, Caatinga and Pampa biomes had low emissions compared to the Amazon and Cerrado. Based on 2030 projections, the sum of emissions from fire foci in the six Brazilian biomes will exceed 5.7 Gt CO2, compromising the national GHG reduction targets. To reduce GHG emissions, Brazil will need to control deforestation induced by the expansion of the agricultural frontier in the Amazon and Cerrado biomes. This can only be achieved through significant political effort involving the government, entrepreneurs and society as a collective.

Major range extensions for three species of porcupines (Rodentia: Erethizontidae: Coendou) from the Brazilian Amazon / Extensão de distribuição de três espécies de porcos-espinhos, gênero Coendou (Rodentia: Erethizontidae) da Amazônia brasileira

Abstract: We report range extensions for three species of Amazonian erethizontids, Coendou bicolor, C. ichillus, and C. nycthemera. We record C. ichillus for the first time in Brazil, from Rio Japurá, state of Amazonas. We record C. bicolor for the first time in the state of Amazonas, which represents a range extension of approximately 905 km. We also extend the occurrence of C. nycthemera 620 km to the south into Mato Grosso state. All records are based on museum specimens, highlighting the importance of scientific collections as biodiversity databases and emphasizing the lack of research on Amazonian porcupines.

Resumo: Aqui nós relatamos ampliação de distribuição de três espécies de eretizontídeos amazônicos: Coendou bicolor, C. ichillus e C. nycthemera. Nós registramos pela primeira vez C. ichillus no Brasil, no Rio Japurá, estado do Amazonas. Registramos C. bicolor pela primeira vez no estado Amazonas, o que representa uma ampliação de distribuição de aproximadamente 905 km. Também estendemos a ocorrência de C. nycthemera 620 km ao sul, no estado de Mato Grosso. Todos os registros são baseados em espécimes de museu, enfatizando a importância das coleções científicas como bancos de dados da biodiversidade e a destacando ausência de pesquisas para porcos-espinhos amazônicos.

New records of three Neotropical arboreal ant species of Camponotus, subgenus Dendromyrmex (Hymenoptera: Formicidae) for the southern Amazon, including biological information / Novos registros de três espécies neotropicais de formigas arborícolas de Camponotus, subgênero Dendromyrmex (Hymenoptera: Formicidae) para a Amazônia meridional, incluindo dados de história natural

Camponotus (Formicinae) is the most specious and abundant genus of the family Formicidae. The genus is represented by ants that both forage and nest in the most diverse terrestrial and arboreal environments. Among the arboreal species of Camponotus are those of the subgenus Dendromyrmex. We recorded, for the first time, evidence of Camponotus chartifex (Smith, 1860) in the state of Mato Grosso, Brazil, and expanded the distributions of Camponotus nidulans (Smith, 1860) and Camponotus apicalis (Mann, 1916). We include information on the biology of the species and a discussion on the sampling of arboreal and winged ants. (AU)

Camponotus é um dos gêneros mais especiosos e abundantes da subfamília Formicidae. O gênero é representado por formigas que se alimentam e nidificam nos mais diversos habitats de ambientes terrestres e arbóreos. Entre as espécies arborícolas de Camponotus, estão as do subgênero Dendromyrmex. Registramos, pela primeira vez, Camponotus chartifex (Smith, 1860) para o estado de Mato Grosso, Brasil, e expandimos a distribuição de Camponotus nidulans (Smith, 1860) e Camponotus apicalis (Mann, 1916), incluindo informações biológicas sobre as espécies e uma discussão sobre a amostragem de formigas arborícolas e aladas.(AU)

Morfologia da traqueia e lobação pulmonar de Leopardus pardalis (jaguatirica) / Morphology of the trachea and lung lobation of Leopardus pardalis (ocelot)

A espécie Leopardus pardalis, conhecida popularmente como jaguatirica, é um felino de médio porte com ampla distribuição em território nacional e está incluída na lista de espécies da fauna brasileira ameaçadas de extinção. Este estudo teve como objetivo caracterizar os aspectos macroscópicos e microscópico da traqueia e lobos pulmonares em L. pardalis. As análises foram feitas utilizando cinco exemplares de jaguatirica, sendo dois machos e três fêmeas, adultos, três desses exemplares foram a óbito por atropelamento em rodovias próximas ao município de Alta Floresta, e dois doados após a morte pelo IBAMA ao o Laboratório de Zoologia e Morfologia Animal. Nos espécimes a traqueia era um tubo flexível formado por pares de arcos cartilaginosos, apresentando epitélio pseudo-estratificado não ciliado no seu revestimento interno, e outros estruturas básicas deste órgão. O pulmão se mostrou como um órgão constituído por lobos separados por fissuras com um parênquima usual aos demais mamíferos descritos. No que diz respeito às caraterísticas anatômicas da traqueia e pulmão se mostraram semelhantes à de outros mamíferos, já nos aspectos microscópicos da traqueia apresentou certas peculiaridades diferindo dos demais trabalhos encontrados. No que tange o aspecto do parênquima pulmonar as características histológicas não variaram com as que estão descritas.(AU)

The species Leopardus pardalis, popularly known as ocelot, is a medium sized cat with wide distribution in the national territory and is included in the list of species of Brazilian fauna threatened with extinction. This study aimed to characterize the macroscopic and microscopic aspects of the trachea and lung lobes in L. pardalis. Analyses were performed using five copies of ocelot, two males and three females, adults, three of these specimens died from being run over on highways nearby the municipality of Alta Floresta, and two donated after death by IBAMA to the Laboratory of Zoology and Animal Morphology. In the trachea specimens was a flexible tube formed by pairs of cartilaginous arches, with pseudo-stratified epithelium ciliated not in its inner lining, and other basic structures of this body. Lung proved as a body made up of lobes separated by cracks with a usual parenchyma to the other described mammals. With respect to the anatomic features of the trachea and lung were similar to other mammals, as in the microscopic aspects of the trachea showed certain peculiarities found differing from the other jobs. Regarding the appearance of the lung parenchyma histological characteristics did not differ with those described.(AU)

Morfologia das glândulas salivares de glironia venusta Thomas, 1912 (didelphimorphia) / Morphology of salivary glands of the glironia venusta Thomas, 1912 (didelphimorphia)

O objetivo deste trabalho foi descrever a morfologia das glândulas salivares de Glironia venusta. Foi utilizado um exemplar coletado no resgate de fauna da Usina Hidroeletrica Teles Pires. Este foi fixado com solução de formaldeído a 10%. Para a análise macroscópica, as glândulas foram dissecadas e fotografadas in situ e para a microscopia foram retirados fragmentos das glândulas. Estes foram desidratados em concentrações crescentes de álcool, diafanizados em xilol, inclusos em parafina e corados com HE. G. venusta apresentou as glândulas mandibulares, parótidas, sublinguais, labiais e zigomáticas. As mandibulares se mostraram como estruturas alongadas, constituídas por lobos não septados e localizadas na porção anterior da região cervical. De formato triangular, a parótida estava localizada na depressão do masseter, ventral à cartilagem auricular. As sublinguais encontravam-se ventrais ao ramo da mandíbula, caudais ao digástrico. Foi observado na porção dorsoposterior à comissura labial, dorsal ao músculo orbicular da boca, as glândulas labiais, que apresentaram formato de "U". Já as glândulas zigomáticas acompanhavam a forma da porção anterior do arco zigomático, na margem infraorbital. As glândulas mandibulares e sublinguais apresentaram ácinos do tipo mucosos, com alguns ácinos serosos. A parótida era constituída por ácinos puramente serosos. Na glândula labial foi observado ácinos do tipo mistos ou seromucosos. Para a glândula zigomática não foi possível a realização da análise microscópica devido problemas de procedimento histológico. As características das glândulas salivares observadas em G. venusta se assemelham a de outros mamíferos onívoros, entretanto, apresentaram pequenas diferenças no que se refere à sua localização e forma.

The aim of this study was to describe the morphology of the salivary glands of Glironia venusta. A sample of G. venusta was collected in fauna rescue of hidroelectric usine of Teles Pires was used. This exemplar was fixed with formaldehyde solution 10%. For macroscopic analysis, the glands were dissected and photographed in situ and for the microscopy fragments of the glands were removed, that were dehydrated in increasing alcohol concentrations, diaphanizated in xylene, included in paraffin and stained with hematoxylin and eosin. G. venusta presented the mandibular, parotid, sublingual, labial and zygomatic glands. The mandible is shown as elongated structures, composed of non-septated lobes and located in the anterior cervical region. With a triangular format, the parotid was located in the depression of the masseter, ventral an auricular cartilage. The sublingual were located ventral to the mandible, caudal to the digastric muscle. In the posterior dorsal portion, until the labial commissure, dorsal to the orbicularis muscle of mouth was observed the labial glands, which showed a "U" shape. The zygomatic glands was accompanied the shape of the anterior portion of the zygomatic arch at the infraorbital margin. The mandibulars and sublinguals glands showed acini of mucous type, with some serous acini. The parotid one was made up purely by serous acini. In the labial gland was observed acini of mixed types mixed or seromucosous. Related the zygomatic gland was not possible to perform the microscopic analysis because of histological proceeding problems. Characteristics of the salivary glands observed in G. venusta resemble other omnivores mammals, but showed small differences as regards their location and shape.

Anatomia da cavidade bucofaringeana de Sorubim trigonocephalus (Siluriformes, Osteichthyes) / Anatomy of the buccopharyngea cavity of Sorubim trigonocephalus (Siluriformes, Osteichthyes)

Sorubim trigonocephalus Miranda et Ribeiro, 1920 conhecido popularmente como chinelo, é uma espécie migratória, de importância econômica. Bastante apreciado na gastronomia por apresentar sabor agradável e sem ossos intermusculares (espinhos). Os exemplares foram coletados em um trecho no Rio Teles Pires, localizado no município de Alta Floresta/MT. Anestesiados e sacrificados em solução aquosa de benzocaína, fixados com solução de formoldeído a 10%, transferidos para o Laboratório de Anatomia Animal/Unemat para descrição das características da cavidade bucofaringeana. Esta espécie apresentou uma pré-maxila bem desenvolvida e cabeça achatada dorsoventralmente, boca localizada na porção ventral média da cabeça, com fenda bucal ampla. Os lábios superiores apresentaram pigmentação cinza escuro com pequenas áreas claras, sendo mais largos que os inferiores e não apresentaram pigmentação. Foram identificadas quatro regiões dentígeras na porção anterior da cavidade bucal e duas na região da faringe, todas com dentes viliformes. A porção posterior da cavidade bucal era limitada lateralmente por quatro pares de arcos branquiais que decresciam em tamanho do primeiro ao último par, crânio-caudal, formados por dois ramos: o superior, mais curto, e o inferior, mais longo. A cavidade bucofaringeana de S. trigonocephalus se mostrou semelhante à de outros teleósteos descritos na literatura, estando adaptado ao hábito alimentar com dieta carnívoro-ictiofágica e diferindo apenas pela ausência de língua estrutural com pré maxila bem desenvolvida apresentando dentes viliformes.

Sorubim trigonocephalus Miranda et Ribeiro, 1920 is popularly known as slipper, migratory specie of economic importance. It is much appreciated in gastronomy because it has good flavor and no intermuscular bones (spines). Specimens were collected on a stretch of the Teles Pires river, located in Alta Floresta/MT, anesthetized and euthanized in aqueous solution of benzocaine, fixed with 10% formaldehyde and transferred to the Laboratory of Animal Anatomy of Unemat to be analyzed and described the characteristics of the buccopharyngeal cavity. With a premaxilla well developed and head dorsoventrally flattened, S. trigonocephalus show out located on the ventral portion of the head mouth wide slit. The upper lip pigmentation had dark gray with small light areas, wider than the and without pigmentation. Was identified four dentigerous regions in in the anterior oral cavity and two in the pharynx region, both with viniliform tooth. The posterior portion of the oral cavity was bounded laterally by four pairs of gill arches that decreased in size from first to last pair, formed by two branches: the higher, shorter, and the lower, longer. The buccopharyngea cavity of S. trigonocephalus showed similar to other teleosts described in the literature, and is adapted to eating habits with diet ictiophagic carnivore and differing only by the absence of a structural tongue and pre maxilla well developed showing viniliform tooth.

Estrutura morfológica do fígado de tambaqui Colossoma macropomum (Cuvier, 1818) / Morphological structure of the liver in tambaqui, Colossoma macropomum (Cuvier, 1818)

Este trabalho teve como objetivo descrever macro e microscopicamente o fígado do Tambaqui Colossoma macropomum, Teleósteo de água doce da Família Characidae, de grande interesse econômico da bacia Amazônica. Foram utilizados seis (6) exemplares jovens com idade entre seis meses e um ano, oriundos da Chácara Esteio, Alta Floresta, MT, que desenvolve principalmente a prática da piscicultura. O órgão foi fotodocumentado in situ e descrito macroscopicamente, em seguida procedeu-se a retirada de fragmentos deste, que foram processados pelas técnicas histológicas rotineiras para inclusão em parafina e coloração de HE. O fígado localizou-se ventral à bexiga natatória e craniodorsalmente ao estômago, apresentou coloração amarronzada a vermelho, constituído por três lobos hepáticos, o lobo lateral direito, o lobo lateral esquerdo e o lobo ventral. Microscopicamente, o parênquima era constituído por hepatócitos com formato que variou do arredondado irregular hexagonal ao redondo com núcleo grande e central, arranjados em cordões lineares limitados por sinusóides que irradiam para veias centrais, e com ausência de lóbulos hepáticos. As veias centrais estavam distribuídas pelo parênquima, enquanto que o espaço porta, na maioria das vezes, era constituído apenas por uma veia hepática e o ducto biliar, em outros locais foi observado, uma artéria e um ducto. Não foi observada a formação de tríades portais. Foram frequentemente observados melano macrófagos centrais dispersos pelo parênquima. O estudo morfofuncional do Aparelho Digestório de peixes da bacia Amazônica, se faz pertinente com vistas ao conhecimento do aproveitamento de ganho de peso e produção em alta escala para consumo humano e preservação da espécie, além da importância de estarem sendo utilizados como bioindicadores atualmente.

This research aimed to describe the macroscopic and microscopic liver of tambaqui, Colossoma macropomum, Teleost freshwater Family Characidae, of great economic interest for the Amazon basin. We used six juveniles aged between six month and one year, from the small holding Esteio, Alta Floresta/MT, that develops mainly fish farming. The body was photographed in situ, described macroscopically, and fragments were removed and processed by routine histological techniques through paraffin embedding and HE staining. The liver, located ventrally to the swim bladder and craniodorsally to the stomach, is brownish red and consisted of three lobes, the right lateral, the left lateral and the ventral lobe. Microscopically, the parenchyma consists of hepatocytes varying from irregular rounded hexagonal to round forms with a large and central nucleus, and arranged in linear strings limited by sinusoids and radiating to central veins, but with absence of liver lobules. The central veins are distributed throughout the parenchyma, while the portal space consists in most cases only of a hepatic vein and bile duct; elsewhere exist artery and duct. Formation of portal triads was not founde. Melano macrophages were frequently seen dispersed throughout the central parenchyma. The morphofunctional study of the digestive system of fishes of the Amazon basin is important to obtain knowledge about their weight gain, large scale production for human consumption and preservation of the species, and has also its importance for being used as bioindicators today.

Histologia e ultraestrutura do rim e rim cefálico do pacu / Histology and ultrastructure of kidney and cephalic kidney in Pacu

O pacu, Piaractus mesopotamicus, é um teleósteo da Família Characidae, intensivamente cultivado no Brasil devido sua rusticidade, crescimento rápido e fácil adaptação. O conhecimento morfológico dos sistemas corpóreos, incluído órgãos linfóide, se faz necessário, para uma melhor produção no cultivo de peixes, fornecendo subsídios na manutenção dos estoques. O objetivo deste estudo foi descrever morfologicamente o rim e rim cefálico de Piaractus mesopotamicus, analisando os perfis celulares de cada órgão com o uso de microscopia de luz e microscopia eletrônica de transmissão. O resultado da análise macroscópica mostrou que a localização do rim e rim cefálico são as mesmas encontradas na maioria dos teleósteos. O rim apresentou uma forma em "H", onde a região média se expandia sobre a bexiga natatória. O rim cefálico se apresentou como uma dilatação na região cranial do rim, mostrando-se bem visível. Na microscopia eletrônica de transmissão também foram observadas similaridades ultraestruturais com outros teleósteos. Observando nossos resultados concluímos que histologicamente e ultraestruturalmente, os órgãos linfóides rim e rim cefálico de Piaractus mesopotamicus são similares aos de outros teleósteos.

The Pacu, Piaractus mesopotamicus, is a teleostei of the Characidae family, intensively cultivated in Brazil due to its rusticity, fast growth and easy adaptation. Morphological knowledge of the body systems including the lymphoid organs is necessary to improve fish production and supply subsidies for the maintenance of stocks. This study aimed to describe morphologically kidney and head kidney of Piaractus mesopotamicus, analyzing the cellular profile of each organ with the use of light microscopy and electronic transmission microscopy. The result of the macroscopic analysis showed that the localization of the kidney and head kidney is the same as found in the majority of the teleostei. The kidney presented a form in "H", where the medium region is expanded on the natatorium bladder. The head kidney presented a dilatation in the cranial region of the kidney. In the transmission electronic microscopy we found ultrastructural similarities with other teleostei fish. It can be concluded that the lymphoid organs (kidney and head kidney) of Piaractus mesopotamicus are histologically and ultra-structurally similar to the other teleostei.