Abstract: Aim To investigate reproductive characteristics in a small population of Psalidodon aff. fasciatus living in isolation in an environment with a unique geological configuration, a doline-shaped depression (known as Furna 2), with a mean diameter of 80 m and water depth of 50 m, a natural heritage of the Vila Velha State Park (VVSP). Methods The fish were collected between February 2019 and January 2020 using nets and pots; standard length and total weight were measured. The gonads were also removed for histological analysis. Estimates were made for the weight-length ratio, the relative condition factor, the sex ratio, and the size at first maturity (L50 and L95) for males and females. Results The five gonadal stages that were characterized (resting, early mature, mature, partially empty, and totally empty) were consistent with what was expected for the species. The results obtained here indicate that these lambaris have an opportunistic (r) life strategy. Compared to previous studies, we discovered that fish of this population start maturing at smaller sizes. Indicating negative allometric growth, the length-weight ratio was WT = 0.0002 * LT2.3039, and the condition index (Kn = 0.95) showed no significant gender differences. When compared to other non-isolated populations of the same species, the population's sex ratio showed an unexpectedly significant male predominance (1M: 0.6 F). Conclusions Our results show an imbalance in the sex ratio, contrary to what would be expected for non-isolated populations. This imbalance may be related to the complete isolation of this environment, suggesting that females may be affected by some evolutionary force, such as inbreeding. However, other factors cannot be ruled out, as the underlying genetic mechanisms remain unknown, and only future investigations can reveal a more complete understanding of reproduction in isolated populations.

Resumo: Objetivo Investigar caracteres reprodutivos em uma pequena população natural de Psalidodon aff. fasciatus que está isolada em um ambiente com rara configuração geológica, uma depressão em forma de dolina (conhecida como Furna 2), com diâmetro médio de 80 m e lâmina d'água de 50 m, patrimônio natural do Parque Estadual de Vila Velha. Métodos Os peixes foram coletados entre fevereiro de 2019 e janeiro de 2020 com redes e covos; foram determinados o comprimento padrão e o peso total, além da remoção das gônadas para análises histológicas. Também, foram estimadas a relação peso-comprimento, o fator de condição relativo, a proporção sexual e o tamanho da primeira maturação (L50 e L95) para machos e fêmeas. Resultados Caracterizamos cinco estádios de desenvolvimento gonadal: repouso, maduro inicial, maduro, parcialmente vazio e totalmente vazio, não diferindo do esperado para a espécie. Os resultados aqui obtidos indicam que esses lambaris possuem estratégia de vida do tipo oportunística (r). Comparado a estudos anteriores, descobrimos que os peixes desta população começam a amadurecer em tamanhos menores. Indicando crescimento alométrico negativo, a relação peso-comprimento foi WT = 0.0002 * LT2.3039, e o fator de condição (Kn = 0.95) não diferiu significativamente entre os sexos. A proporção sexual revelou uma predominância significativa e inesperada de machos (1M: 0,6 F) dentro da população, e também quando comparada com outras populações não isoladas da mesma espécie. Conclusões Nossos resultados revelam um desequilíbrio na proporção sexual, contrastando com o esperado para a espécie em condições de não isolamento. Esse desequilíbrio pode estar relacionado ao isolamento completo desse ambiente, sugerindo que as fêmeas podem estar sendo afetadas por alguma força evolutiva, como a endogamia. No entanto, não podem ser descartados outros fatores, pois, os mecanismos genéticos subjacentes permanecem ainda desconhecidos, somente investigações futuras poderão revelar uma compreensão mais completa da reprodução em populações isoladas.

Abstract The complete mitogenome of four Scleromystax barbatus populations distributed along the species natural range was reconstructed, comprising the first study with this genus and the second with Corydoradinae specimens sampled from their natural environment and deposited in permanent collections. The mitogenome of S. barbatus is a circular molecule of 16,694 base pairs (bp) comprising 37 genes, 22 of which are tRNA, two are rRNA, 13 are protein-coding genes and one control region (D-loop). An 18-nucleotide insertion sequence was found between the ATPase subunit 6 and COIII genes. Most genes are encoded on the heavy strand, while the ND6 and eight tRNAs are found on the light strand. Phylogenetic analyses using other available Callichthyidae mitogenomes confirmed the monophyly of Callichthyinae and Corydoradinae and indicate that S. barbatus populations form a separate and more closely related branch of Corydoras nattereri + Corydoras paleatus.

Resumo O mitogenoma completo de quatro populações de Scleromystax barbatus coletadas ao longo da área de distribuição natural foi reconstruído, compreendendo o primeiro estudo com este gênero e o segundo com espécimes de Corydoradinae amostrados em seu ambiente natural e depositados em coleções permanentes. O mitogenoma de S. barbatus é uma molécula circular de 16.694 pares de bases (pb) compreendendo 37 genes, dos quais 22 são tRNA, dois são rRNA, 13 são genes codificadores de proteínas e uma região controle (D-loop). Uma sequência de inserção de 18 nucleotídeos foi encontrada entre a subunidade 6 da ATPase e os genes COIII. A maioria dos genes é codificada na fita pesada, enquanto o ND6 e oito tRNAs são encontrados na fita leve. Análises filogenéticas usando outros mitogenomas de Callichthyidae disponíveis confirmaram a monofilia de Callichthyinae e Corydoradinae e indicam que as populações de S. barbatus formam um ramo separado e mais intimamente relacionado a Corydoras nattereri + Corydoras paleatus.

Abstract Recently renamed, Psalidodon scabripinnis populations of Serra da Mantiqueira, previously known as Astyanax scabripinnis have been deeply studied in the last years. These populations are small and isolated and occur very close to the watershed between Paraíba do Sul River basin and Upper Paraná River basin, in Serra da Mantiqueira region in the Atlantic Rainforest. These conditions arouse the interest in knowing theor genetic conservation status and how they responded to the separation between the two rivers basins. Therefore, we accessed the genetic diversity of five P. scabripinnis populations of this region with microsatellites and mitochondrial data. The results showed a complex structure pattern that doesn’t match the simple basin separation and a reasonably conservation status when compared with other populations of the same family or with similar natural history.

RESUMO - RACIONAL: O diabetes tipo 2 (DM2) é uma doença de impacto mundial que tem levado ao aumento de comorbidades e mortalidade em vários países. A imunoexpressão dos hormônios incretínicos glp-1 e pyy3-36, pode ser usada como marcador no trato gastrointestinal para analisar a atividade da célula L em resposta ao tratamento do DM2. OBJETIVO: O presente estudo teve como objetivo investigar a presença, localização e secreção de células L no intestino delgado de pacientes submetidos à forma de cirurgia bariátrica denominada gastroenteromentectomia adaptativa com bipartição parcial. MÉTODOS: Ensaios imunohistoquímicos, reação quantitativa em cadeia de polimerase em tempo real (qPCR) e análise de manchas ocidentais foram realizados em amostras de mucosa intestinal de pacientes com diabetes tipo 2 nos períodos pré- e pós-operatório. RESULTADOS: Todos os resultados foram consistentes e indicaram expressão basal e secreção de peptídeos glucagon-1 (GLP-1) e peptídeos YY (PYY3-36) incretinas por células L. Uma maior densidade de células foi demonstrada nas porções mais distais do intestino delgado. Não foi encontrada diferença significativa entre os níveis de expressão GLP-1 e PYY3-36 nos períodos pré-operatório e pós-operatório, provavelmente devido ao estado de jejum prolongado durante o qual as amostras foram coletadas CONCLUSÃO: O maior número de células L em atividade implica melhor sinalização de peptídeo, resposta e funcionamento do sistema neuroendócrino.

ABSTRACT - BACKGROUND: Type 2 diabetes mellitus (T2DM) is a disease of global impact that has led to an increase in comorbidities and mortality in several countries. Immunoexpression of the incretin hormones such as glucagon-like peptide-1 (GLP-1) and peptide YY (3-36) (PYY3-36) can be used as a scorer in the gastrointestinal tract to analyze L-cell activity in response to T2DM treatment. OBJECTIVE: This study aimed to investigate the presence, location, and secretion of L cells in the small intestine of patients undergoing the form of bariatric surgery denominated adaptive gastroenteromentectomy with partial bipartition. METHODS: Immunohistochemical assays, quantitative real-time polymerase chain reaction (qPCR), and Western blot analysis were performed on samples of intestinal mucosa from patients with T2DM in both the preoperative and postoperative periods. RESULTS: All results were consistent and indicated basal expression and secretion of GLP-1 and PYY3-36 incretins by L cells. A greater density of cells was demonstrated in the most distal portions of the small intestine. No significant difference was found between GLP-1 and PYY3-36 expression levels in the preoperative and postoperative periods because of prolonged fasting during which the samples were collected. CONCLUSION: The greater number of L cells in activity implies better peptide signaling, response, and functioning of the neuroendocrine system.

RESUMO RACIONAL: As células L enteroendócrinas podem ser encontradas na extensão de todo trato gastrointestinal e suas incretinas atuam no controle glicêmico e da homeostase metabólica. Estudos mostram que pacientes obesos graves com diabetes mellitus tipo 2 apresentam má sinalização entero-hormonal e baixa resposta da secreção do peptídeo glucagon-1, que poderia ser explicado por uma densidade menor de células L ou uma distribuição mais distal ao longo do intestino delgado. OBJETIVOS: Analisar a diferença da densidade de células L nos segmentos do intestino delgado de pacientes obesos graves submetidos à gastroplastia em Y de Roux, em período pós-operatório tardio, com padronização de alça alimentar e biliopancreática com extensão de 60 cm em ambas. MÉTODOS: Ensaios de análises de imuno-histoquímica foram feitos a partir de biopsias intestinais obtidas em três segmentos: junto à anastomose gastrointestinal (AGI= Ponto A), junto à anastomose entero-enteral (AEE= Ponto B= 60 cm distal à AGI) e 60 cm distalmente à anastomose entero-enteral (Ponto C). Os resultados foram obtidos por meio de imunomarcação do peptídeo glucagon-1 secretado pelas células L. RESULTADOS: Foi observada maior densidade de células L na porção mais distal do intestino delgado (Ponto C) quando comparada às porções mais proximais (Ponto A e B). CONCLUSÕES: Em pacientes no pós-operatório de gastroplastia em Y de Roux, identificou-se concentração maior de células L já na porção a 60 cm distalmente a entero-entero anastomose quando comparada aos segmentos proximais, o que pode explicar diferenças na sensibilização no lúmen intestinal e na resposta entero-hormonal.

ABSTRACT BACKGROUND: Enteroendocrine L cells can be found in the entire gastrointestinal tract and their incretins act on glycemic control and metabolic homeostasis. Patients with severe obesity and type 2 diabetes mellitus may have lower density of L cells in the proximal intestine. AIMS: This study aimed to analyze the density of L cells in the segments of the small intestine in the late postoperative of Roux-en-Y gastric bypass in diabetic patients with standardization of 60 cm in both loops, alimentary and biliopancreatic. METHODS: Immunohistochemistry analysis assays were made from intestinal biopsies in three segments: gastrointestinal anastomosis (GIA= Point A), enteroenteral anastomosis (EEA= Point B= 60 cm distal to the GIA) and 60 cm distal to the enteroenteral anastomosis (Point C). RESULTS: A higher density of L cells immunostaining the glucagon-1 peptide was observed in the distal portion (Point C) when compared to the more proximal portions (Points A and B). CONCLUSIONS: The concentration of L cells is higher 60 cm distal to enteroenteral anastomosis when comparing to proximal segments and may explain the difference in intestinal lumen sensitization and enterohormonal response after Roux-en-Y gastric bypass.

Abstract The aim of this paper was to present the second case of B chromosomes in Auchenipteridae (Trachelyopterus sp.), and to test the hypothesis that the B chromosomes of this species and Parauchenipterus galeatus might have a common origin, since these two species have phylogenetic proximity. Both species have 58 chromosomes in the A complement, heterochromatin preferentially located at terminal region of the most of chromosomes, simple Ag-NORs located at the short arm of a subtelocentric pair, which was confirmed by hybridization with 18S rDNA, two submetacentric pairs carrying 5S rDNA sites, and presence of B chromosomes. The B chromosomes of the two species are small, metacentric, and almost totally heterochromatic, with variation of number intra and interindividual. In addition, for the first time in fish, the telomeric sequence [TTAGGG]n was dispersed along the B chromosomes (both species). The [GATA]n microsatellite were scattered in all chromosomes of the A complement and absent in the B chromosomes, in both species. These aspects confirm the phylogenetic proximity between the genus Parauchenipterus and Trachelyopterus, and they suggest the hypothesis that the B chromosomes of the two species might have common origin, previous to the diversification of these genera.

Abstract Supernumerary, or B, chromosomes are present in several eukaryotes, including characid fish of the genus Psalidodon. Notably, Psalidodon paranae carries the most studied B chromosome variant, a macro-B chromosome. The origin of this element was determined to be an isochromosome; however, data regarding its inheritance remain unavailable due to methodological barriers such as the lack of an efficient, non-invasive, and rapid protocol for identifying B-carrying individuals that would enable the design of efficient crossing experiments. Thus, in this study, we primarily aimed was to develop two non-invasive and fast (approximately 2 h) methods to identify the presence of B chromosomes in live specimens of P. paranae based on satellite DNA (satDNA) sequences known to be present in this element. The methods include fluorescence in situ hybridization in interphase nuclei and relative gene quantification of satDNAs using quantitative polymerase chain reaction. Our results reveal the efficiency of quick-fluorescence in situ hybridization and quantitative polymerase chain reaction for identifying B-carrying individuals using the proposed satDNA sequences and open up new possibilities to study B chromosomes.

Abstract The aims of this study were to evaluate the homology of the ZmMATE1 and ZmMATE2 gene sequences with those deposited in the international banks of sequences and quantify the differential expression of the genes ZmMATE1, ZmMATE2, and ZmNrat1 in germplasms of landrace and hybrid maize under aluminum (Al) stress in minimal solution. Fifty-two hybrids from different companies and 50 landrace varieties were genotyped for the genes ZmMATE1 and ZmMATE2. For studies of gene expression, the tolerant (H 44 and V 18) and the sensitive (H 22 and V 25) genotypes were exposed to minimal solution containing 4 mg L-1 of Al for different periods (0, 1, 3, 6, 9, 12, 24, and 48 h). The results showed greater differential expression in the tolerant V 18 landrace variety of the gene ZmMATE1, indicating that exudation of citrate may be the main mechanism of Al tolerance in this genotype.

Abstract B chromosomes are non-essential additional genomic elements present in several animal and plant species. In fishes, species of the genus Psalidodon (Characiformes, Characidae) harbor great karyotype diversity, and multiple populations carry different types of non-essential B chromosomes. This study analyzed how the dispensable supernumerary B chromosome of Psalidodon paranae behaves during meiosis to overcome checkpoints and express its own meiosis-specific genes. We visualized the synaptonemal complexes of P. paranae individuals with zero, one, or two B chromosomes using immunodetection with anti-medaka SYCP3 antibody and fluorescence in situ hybridization with a (CA)15 microsatellite probe. Our results showed that B chromosomes self-pair in cells containing only one B chromosome. In cells with two identical B chromosomes, these elements remain as separate synaptonemal complexes or close self-paired elements in the nucleus territory. Overall, we reveal that B chromosomes can escape meiotic silencing of unsynapsed chromatin through a self-pairing process, allowing expression of their own genes to facilitate regular meiosis resulting in fertile individuals. This behavior, also seen in other congeneric species, might be related to their maintenance throughout the evolutionary history of Psalidodon.

Abstract Hummingbirds (Trochilidae) are one of the most enigmatic avian groups, and also among the most diverse, with approximately 360 recognized species in 106 genera, of which 43 are monotypic. This fact has generated considerable interest in the evolutionary biology of the hummingbirds, which is reflected in a number of DNA-based studies. However, only a few of them explored chromosomal data. Given this, the present study provides an analysis of the karyotypes of three species of Neotropical hummingbirds, Anthracothorax nigricollis (ANI), Campylopterus largipennis (CLA), and Hylocharis chrysura (HCH), in order to analyze the chromosomal processes associated with the evolution of the Trochilidae. The diploid number of ANI is 2n=80 chromosomes, while CLA and HCH have identical karyotypes, with 2n=78. Chromosome painting with Gallus gallus probes (GGA1-12) shows that the hummingbirds have a karyotype close to the proposed ancestral bird karyotype. Despite this, an informative rearrangement was detected: an in-tandem fusion between GGA7 and GGA9 found in CLA and HCH, but absent in ANI. A comparative analysis with the tree of life of the hummingbirds indicated that this fusion must have arisen following the divergence of a number of hummingbird species.

RESUMO Introdução: A rede de questões fisiológicas envolvidas na cirurgia metabólica é muito complexa. No entanto, a anatomia e fisiologia comparadas podem fornecer boas pistas sobre como o trato digestivo é moldado para alimentos mais ou menos calóricos, para mais ou menos fibras, para abundância e escassez. Objetivo: Selecionar e analisar dados de Ciências Evolucionárias e Anatomia e Fisiologia Comparadas que ajudam na compreensão da cirurgia metabólica. Método: Revisão focada da literatura, selecionando informações desses três campos de conhecimento em bancos de dados da Cochrane Library, Medline e SciELO, artigos e capítulos de livros em inglês e português, entre 1950 e 2019, usando como descritores “GIP, GLP-1, PYY, type 2 diabetes, vertebrates digestive system, hominid evolution, obesity, bariatric surgery”. Resultado: O trato digestivo de animais superiores mostra órgãos altamente especializados para digerir e absorver dietas específicas..A parte proximal, diante da escassez de açúcares, é basicamente dedicada à geração de açúcar a partir de diferentes substratos (gliconeogênese). As tarefas básicas do intestino proximal consistem em fornecer proporcionalmente açúcares livres, insulina e outros combustíveis e gerar elementos anabólicos no sangue, alguns deles obesogênicos. Limitar a ingestão pela saciedade, por diminuir o esvaziamento gástrico e limitar a elevação excessiva dos principais combustíveis (açúcar e gordura) no sangue são principalmente as tarefas metabólicas do intestino distal. Mudança rápida e profunda na composição da dieta humana causa elevação nas atividades endócrinas e metabólicas do intestino proximal e redução no intestino distal. Os modelos mais eficientes de cirurgia metabólica fazem ajustes nesse equilíbrio proximal-distal das atividades metabólicas intestinais. Conclusão: A cirurgia metabólica funciona basicamente fazendo ajustes nas atividades metabólicas do intestino proximal e distal que se assemelham à ação da seleção natural no desenvolvimento dos sistemas digestivos de animais superiores.

ABSTRACT Introduction: The wide net of physiological issues involved in metabolic surgery is extremely complex. Nonetheless, compared anatomy and phisiology can provide good clues of how digestive tracts are shaped for more or less caloric food, for more or less fiber, for abundance and for scarcity. Objective: To review data from Compared Anatomy and Physiology, and in the Evolutionary Sciences that could help in the better comprehension of the metabolic surgery. Method: A focused review of the literature selecting information from these three fields of knowledge in databases: Cochrane Library, Medline and SciELO, articles and book chapters in English and Portuguese, between 1955 and 2019, using the headings “GIP, GLP-1, PYY, type 2 diabetes, vertebrates digestive system, hominid evolution, obesity, bariatric surgery “. Results: The digestive tract of superior animals shows highly specialized organs to digest and absorb specific diets. In spite of the wide variations of digestive systems, some general rules are observed. The proximal part of the digestive tract, facing the scarcity of sugars, is basically dedicated to generate sugar from different substrates (gluconeogenesis). Basic proximal gut tasks are to proportionally input free sugars, insulin, other fuels and to generate anabolic elements to the blood, some of them obesogenic. To limit the ingestion by satiety, by gastric emptying diminution and to limit the excessive elevation of major fuels (sugar and fat) in the blood are mostly the metabolict asks of the distal gut. A rapid and profound change in human diet composition added large amounts of high glycemic index foods. They seem to have caused an enhancement in the endocrine and metabolic activities of the proximal gut and a reduction in these activities of the distal gut. The most efficient models of metabolic surgery indeed make adjustments in this proximal/distal balance in the gut metabolic activities. Conclusion: Metabolic surgery works basically by making adjustments to the proximal and distal gut metabolic activities that resemble the action of natural selection in the development the digestive systems of superior animals.

Abstract Background Among Neotropical fishes, the family Characidae is highly diverse and speciose and its taxonomy is not completely resolved. In Chile, the family is represented by five species, all within the genus Cheirodon , of which C. pisciculus, C. galusdae, C. kiliani , and C. australe are endemic , while C. interruptus is introduced. We compared chromosomal markers in order to appreciate the taxonomy and evolution of these trans-Andean fishes. Results The specimens were photographed in stereomicroscope to observe the ventral protrusive teeth and cusps for morphological analysis and species identification. All of the species analysed had equally diploid chromosome number 2n = 50, with karyotypes dominated by high number of acrocentric chromosomes as compared to those of other members of Cheirodontinae. The distribution of heterochromatin was inconspicuous and was similar in all the species. The number of active NORs (nucleolus organizer regions) was polymorphic, with the greater number of them in C. kiliani and C. galusdae . The location of 5S and 18S rDNA ranged in number and position, showing two sites in different chromosomes. The fluorescent in situ hybridization with telomeric probe did not reveal interstitial sites in all analysed species. Conclusions The comparative analysis of karyotypes and morphological markers revealed a biogeographic pattern of distribution, with the species that occur in the southern region forming one group and those in central and northern Chile forming another.

Objective The aim of this study was to evaluate the genetic expression of adipokines in the adipocytes of monosodium glutamate (MSG)-treated obese rats submitted to physical activity.Materials and methods Obesity was induced by neonatal MSG administration. Exercised rats (MSG and control) were subjected to swim training for 30 min for 10 weeks, whereas their respective controls remained sedentary. Total RNA was obtained from sections of the mesenteric adipose tissue of the rats. mRNA levels of adiponectin (Adipoq), tumor necrosis factor alpha (Tnf), peroxisome proliferator-activated receptor alpha (Ppara), and peroxisome proliferator-activated receptor gamma (Pparg) adipokines were quantified by quantitative Real-Time Polymerase Chain Reaction (qRT-PCR).Results In the exercise-trained control group, the expression of Adipoq increased compared to the sedentary control, which was not observed in the MSG-obese rats. Increased levels of Tnf in MSG-obese rats were not reversed by the swim training. The expression of Ppara was higher in sedentary MSG-obese rats compared to the sedentary control. Swimming increased this adipokine expression in the exercise-trained control rats compared to the sedentary ones. mRNA levels of Pparg were higher in the sedentary MSG-rats compared to the sedentary control; however, the exercise did not influenced its expression in the groups analyzed.Conclusions In conclusion, regular physical activity was not capable to correct the expression of proinflammatory adipokines in MSG-obese rat adipocytes.

Parodontidae fish show few morphological characteristics for the identification of their representatives and chromosomal analyses have provided reliable features for determining the interrelationships in this family. In this study, the chromosomes of Apareiodon hasemani from the São Francisco River basin, Brazil, were analyzed and showed a karyotype with 2n = 54 meta/submetacentric chromosomes, and a ZZ/ZW sex chromosome system. The study revealed active NORs located on pair 11 and additional 18S rDNA sites on pairs 7 and 22. The 5S rDNA locus was found in pair 14. It showed a pericentric inversion regarding the ancestral condition. The satellite DNA pPh2004 was absent in the chromosomes of A. hasemani, a shared condition with most members of Apareiodon. The WAp probe was able to detect the amplification region of the W chromosome, corroborating the common origin of the system within Parodontidae. These chromosomal data corroborate an origin for the ZW system of Parodontidae and aid in the understanding of the differentiation of sex chromosome systems in Neotropical fishes.

Dados cariotípicos são apresentados para quatro espécies da família Pimelodidae. Todas apresentaram o mesmo número diploide, 2n = 56 cromossomos, com diferenças nas fórmulas cariotípicas. As espécies aqui analisadas mostraram pouca quantidade de heterocromatina localizada preferencialmente na região centromérica e telomérica de alguns cromossosmos do complemento cariotípico. As regiões organizadoras de nucléolo (Ag-RONs) e a localização dos genes ribossomais pela hibridização in situ fluorescente (FISH), com sondas 18S e 5S, evidenciaram somente um par cromossômico marcado portador de genes ribossomais, à exceção de Pimelodus britskii que apresentou NORs múltiplas e localização sintênica das sondas 18S e 5S. Eventos não-Robertsonianos, como inversão pericêntrica e duplicação das NORs são requeridos para explicar a diversificação cariotípica em Pseudoplatystoma do rio Paraguai (MS), Pimelodus do rio Iguaçu (PR), Sorubim do rio Paraguai (MS) e Steindachneridion do rio Paraíba do Sul (SP). Os dados obtidos para a macroestrutura cariotípica destas espécies corrobora um padrão conservado observado na família Pimelodidae. Por outro lado, evidências de variações interespecíficas pelos marcadores de citogenética molecular empregados possibilitam inferências citotaxonômicas e diferenciação das espécies aqui analisadas.

Karyotypic data are presented for four species of fish belonging to the Pimelodidae family. These species show a conserved diploid number, 2n = 56 chromosomes, with different karyotypic formulae. The analyzed species showed little amount of heterochromatin located preferentially in the centromeric and telomeric regions of some chromosomes. The nucleolus organizer regions activity (Ag-NORs) and the chromosomal location of ribosomal genes by fluorescent in situ hybridization (FISH), with 18S and 5S probes, showing only one chromosome pair marked bearer of ribosomal genes, the only exception was Pimelodus britskii that presented multiple NORs and syntenic location of the 18S and 5S probes. Non-Robertsonian events, as pericentric inversion and NORs duplication are requested to explain the karyotype diversification in Pseudoplatystoma from the rio Paraguay (MS), Pimelodus from the rio Iguaçu (PR), Sorubim from the rio Paraguay (MS) and Steindachneridion from the rio Paraíba do Sul (SP). The obtained data for the karyotype macrostructure of these species corroborates a conserved pattern observed in Pimelodidae. On the other hand, interspecific variations detected by molecular cytogenetics markers made possible cytotaxonomic inferences and differentiation of the species here analyzed.