Abstract Cytogenetic studies in the subfamily Potamotrygoninae have provided valuable insights into the understanding of the evolution and diversification of its species. In the present study, the chromosomal features of seven nominal potamotrygonin species are provided: Plesiotrygon iwamae (2n=74, FN=120), Potamotrygon amazona (2n=66, FN=107), P. constellata (2n=66, FN=110), P. leopoldi (2n=64, FN=102), P. motoro (2n=66, FN=106) from four different localities, and P. orbignyi (2n=66, FN=106), P. scobina (2n=66, FN=104), from Central Amazon. Additionally, we found a new karyomorph in P. wallacei. We considered the localization of Nucleolus Organizer Regions (NORs), as well as the pattern of constitutive heterochromatin, as species-specific characters. We found an XX/XY sex chromosome system in P. orbignyi, and we suggest that P. scobina and P. amazona also possess the same sex chromosome system. Overall, the chromosomal evolution in this group appears to have progressed towards a reduction in diploid number, with a concomitant increase in the number of bi-armed and nucleolar chromosomes.

<p>Os peixes ornamentais da Amazônia são exportados em larga escala para os maiores centros de distribuição e venda de peixes ornamentais do mundo localizados nos EUA, Japão e Alemanha e pelo menos oito espécies destacam-se na aquariofilia. Estas espécies são coletadas no médio e alto rio Negro, no município de Barcelos, no Estado do Amazonas, que responde por cerca de 70% das exportações de peixes ornamentais do Brasil e gera lucros anuais de mais de 6 milhões de dólares. Devido ao intenso comércio de peixes ornamentais na região, importadores de peixes do Amazonas questionaram a sanidade dos animais frente a microrganismos, com destaque para bactérias e vírus causadores de enfermidades. As doenças bacterianas e virais podem ocorrer em todas as espécies de peixes mantidas sob condições de exploração, causando perdas econômicas significativas. Neste trabalho objetivou-se, verificar a ocorrência de bactérias potencialmente patogênicas em peixes ornamentais comercializados e exportados do estado do Amazonas. A caracterização bioquímica de bactérias isoladas em cinco espécies de peixes ornamentais permitiu indicar que os isolados pertencem a espécies de quatro gêneros (<italic>Staphylococcus</italic>, <italic>Nocardia, Acinetobacter</italic>e <italic>Lactococcus</italic>), cujos gêneros bacterianos englobam importantes patógenos causadores de mortalidades em peixes marinhos e de água doce. Embora a biodiversidade Amazônica seja grande, poucos são os trabalhos para investigar essa complexidade, principalmente relacionados à presença de bactérias causadoras de patogenias em peixes ornamentais. Os resultados obtidos demonstram ocorrência de bactérias patogênicas ou com potencial patogênico atuando em diferentes espécies de peixes ornamentais comercializados e exportados do estado do Amazonas.</p>

<p>Ornamental fish in the Amazon are largely exported to the major centers of distribution and sale of ornamental fish in the world, located in the USA, Japan and Germany and at least eight species stand out as major. These species are collected in the medium and upper Rio Negro, in the municipality of Barcelos, in the state of Amazonas, which accounts for about 70% of exports of ornamental fish from Brazil and generating annual revenues of more than 6 million dollars. Because of the intense ornamental fish trade in the region, importers of fish from the Amazon have questioned the sanity of these animals about microorganisms, especially bacteria and viruses that cause disease in these animals. Bacterial and viral diseases can occur in all species of fish maintained under conditions of exploitation causing significant economic losses. Our goal was to verify the occurrence of potentially pathogenic bacteria in ornamental fishes exported from the state of Amazonas. Biochemical characterization of bacterial isolates from five species of ornamental fish allowed the identification of genus (<italic>Staphylococcus</italic>,<italic>Nocardia</italic>, <italic>Acinetobacter</italic> and<italic>Lactococcus</italic>), with important bacterial species causing mortalities in marine and freshwater fish. While Amazon has great biodiversity, there are few studies to investigate this complexity, mainly related to the presence of pathogens causing bacterial diseases on ornamental fish. The results demonstrate the occurrence of pathogenical bacteria or with pathogenic potential in different species of ornamental fish traded from the state of Amazonas.</p>

Karyotypes of six cichlid species of the genus Crenicichla were investigated. The species C. cincta, C. inpa, C. reticulata, C. lugubris, and C. cf. johanna were collected from Amazon basin, and C. britskii was collected from the Paraná-Paraguai basin. All of the analysed species showed 2n = 48 chromosomes; however, C. cincta, C. lugubris, C. cf. johanna, and C. britskii had a karyotype formula of 8M-SM+40ST-A, FN = 56, while C. inpa and C. reticulata exhibited the formula 6M-SM+42ST-A, FN = 54. Analysis of active Ag-NORs revealed two NOR-bearing chromosomes in all species; however, theses cistrons were located on different chromosome pairs and/or in different chromosome locations in each species. This condition bears evolutionary significance, since it is the main chromosome marker of the process of karyotypic evolution among the species of the genus Crenicichla. In general, C-banding revealed a similar constitutive heterochromatin pattern in all species, although it was possible to detect some features that led us to infer that Crenicichla also presents a species-specific heterochromatin pattern.

Comparative cytogenetic analyses of hatchetfishes Carnegiella marthae and Carnegiella strigata (Gasteropelecidae) from the Rio Negro basin were performed using conventional Giemsa staining, silver (Ag) -staining and C-banding. The diploid chromosome numbers of both species equaled 2n = 50 but their karyotypes were distinct. We found evidence for sex chromosomes in C. marthae since karyotype of males presented 20 M + 12 SM + 4 ST + 14 A and ZZ ST chromosomes while the females presented 20 M + 12 SM + 4 ST + 14 A and ZW ST chromosomes of distinct size. Conversely, C. strigata presented 4 M + 4 SM + 2 ST + 40 A chromosomes without sex chromosome heteromorphism. Karyotypes of both species had two NOR-bearing SM chromosomes of distinct size indicating the presence of multiple NOR phenotypes. The sex chromosome pair had specific C-banding pattern allowing identification of both Z and W. This heteromorphic system has previously been described for the gasteropelecids.

Bioensaios sob condições de laboratório foram realizados em larvas de Anopheles darlingi e Culex quinquefasciatus, visando determinar a atividade larvicida de Bacillus sphaericus. Para estimar a toxicidade através da concentração letal mediana (CL50) e a potência das estirpes em relação à estirpe padrão 2362, foi realizada a análise de probit utilizando o programa POLO-PC. Os resultados da CL50 apontaram alta efetividade para as estirpes IB15 (0,040 ppm), IB19 e S1116 (0,048 ppm), IB16 (0,052 ppm) e S265 (0,057 ppm). A estirpe IB15 apresentou potência cerca de 50% maior que a estirpe 2362 nos bioensaios realizados com A. darlingi. Foi observado que as estirpes IB16 e S1116 foram as mais tóxicas para controle de C. quinquefasciatus, mostrando-se cerca de 300-400% mais potente. Os resultados mostram que a avaliação em laboratório é uma importante etapa para selecionar bactérias com ação entomopatogênica a serem usadas na para a produção de biolarvicidas para uso nos criadouros das larvas de mosquitos.

Bioassays under laboratory conditions aiming to determine the larvicidal activity of Bacillus sphaericus were carried out on Anopheles darlingi and Culex quinquefasciatus. In order to estimate the toxicity through median lethal concentration (LC50) and the relative potency of the strains to B. sphaericus standard strain 2362, probit analysis was performed utilizing the POLO-PC program. The findings of LC50 pointed out high effectiveness on strains IB15 (0.040 ppm), IB19 and S1116 (0.048 ppm), IB16 (0.052 ppm) and S265 (0.057 ppm). Strain IB15 presented nearly 50% more potency than strain 2362 in bioassays conducted on A. darlingi. It was observed that IB16 and S1116 strains were the most powerful against C. quinquefasciatus, showing to be about 300-400% stronger than 2362 strain. The results show that laboratory conditioned evaluation can be an important way to select promising bacteria with entomopathogenic action on biolarvicides production for use on mosquitoes breeding sites.

We have analyzed the sequenced genomes of three strains of Mycoplasma hyopneumoniae and one strain of M. synoviae, and have found three and two different transposable element families, respectively in each species. In M. hyopneumoniae, the Insertion Sequences of the IS4 family is represented by ISMHp1, a putatively active element. The IS3 family is represented by several degenerated sequences. A third element called tMH was found, which shows some characteristics reminiscent of retrotransposons. In M. synoviae, three different possibly active IS4 elements are present (ISMHp1-like; ISMs1 and IS1634-like elements). The IS30 family is represented by the degenerated IS1630-like element. The IS1634-like element is shown to be involved in chromosomal rearrangements and horizontal gene transfer (HGT). The ISMHp1-like element is shown to relate to the HGT of a 25-kb region from M. gallisepticum to M. synoviae. The fractions of these genomes that correspond to mobile elements varied from 1.35 to 3.13% in M. hyopneumonia strains and was 2.08% in M. synoviae. Although these species possess reduced genomes, they maintain mobile elements, perhaps as a mechanism for genetic variability production.

This study presents additional genetic data on piranha (Serrasalmus rhombeus Linnaeus, 1766) complex previously diagnosed due to the presence of distinct cytotypes 2n = 58 and 2n = 60. Three esterase-D enzyme loci (Est-D1, Est-D2 and Est-D3) were examined and complemented with chromosomal data from 66 piranha specimens collected from Lake Catalão. For all specimens the Est-D1 and Est-D2 loci were monomorphic. In contrast, the Est-D3 locus was polymorphic with genotypes and alleles being differentially distributed in the previously described cytotypes and served as the basis for detecting a new cytotype (2n = 60 B). In cytotype 2n = 58 the Est-D3 locus was also polymorphic and presented Mendelian allelic segregation with four genotypes (Est-D3(11), Est-D3(12), Est-D3(22) and Est-D3(33)) out of six theoretically possible genotypes, presumably encoded by alleles Est-D3¹ (frequency = 0.237), EsT-D3² (0.710) and Est-D3³ (0.053). A Chi-squared (chi2) test for Hardy-Weinberg equilibrium was applied to the Est-D3 locus and revealed a genetic unbalance in cytotype 2n = 58, indicating the probable existence in the surveyed area of different stocks for that karyotypic structure. A silent null allele (Est-D3(0)) with a high frequency (0.959) occurred exclusively in the 2n = 60 cytotype. On the other hand, the new cytotype 2n = 60 B described here for the first time was monomorphic for the presumably fixed Est-D3³ allele. The data as a whole should contribute to the better understanding the rhombeus complex taxonomic status definition in the Central Amazon.

Descreve-se pela primeira vez o cariótipo de exemplares de S. spilopleura da Amazônia Central. Todos os indivíduos analisados apresentaram número diplóide igual a 60 cromossomos, em conformidade com os dados da espécie obtidos em indivíduos da bacia do Paraná-Paraguai. No entanto, dois citótipos foram encontrados em simpatria na região de confluência dos rios Negro e Solimões, os quais não estão relacionados a heteromorfismo sexual. Além disso, os dois citótipos da Amazônia diferem dos três anteriormente descritos em exemplares do Paraná-Paraguai. A presença de distintos citótipos encontrados em simpatria e alopatria para S. spilopleura nos leva a sugerir que, ou essa espécie apresenta uma ampla heterogeneidade cariotípica ou existe um complexo de espécies cuja morfologia é muito semelhante.

The karyotype of Serrasalmus spilopleura from the Central Amazon is reported here for the first time. All analized individuals showed 60 chromosomes, as observed in previously published karyotypes of this species from the Paraná-Paraguai basin. However, two different cytotypes were found in sites near the confluence of the Negro and Solimões rivers, where the specimens were collected. Such karyotypic differences were not related to sex differentiation. Moreover, the two amazon cytotypes are different from the three cytotypes described in animals from Paraná-Paraguai basin. The different karyotypes detected so far, in both simpatry and allopatry conditions, suggest that S. spilopleura may be either a cytogenetically heterogeneous species or a complex of sibling species.

Foram estudados, pela primeira vez, os cariótipos de duas espécies de sciaenídeos de água doce, pertencentes ao gênero Plagioscion (P. squamosissimus e Plagioscion sp.), através de técnicas de coloração convencional (Giemsa), NOR e banda C. Todos os indivíduos apresentaram 2n = 48, NOR simples e banda C preferencialmente pericentromérica. Porém, a fórmula cariotípica e a localização das NORs permitiram-nos evidenciar diferenças inter- e intra-específicas. Em P. squamosissimus, as NORs estão localizadas em posição proximal nos braços longos do último par do complemento e são heteromórficas em relação ao tamanho das marcações. Aparentemente, esse heteromorfismo de NOR está associado com diferenças populacionais. Por outro lado, Plagioscion sp. apresentou dois citótipos. O citótipo a é caracterizado por 2 cromossomos metacêntricos e 46 acrocêntricos, enquanto o citótipo b é caracterizado por 48 cromossomos acrocêntricos. Em ambos citótipos, as NORs estão localizadas em posição proximal nos braços longos do primeiro par de cromossomos do complemento. Porém, no citótipo a essas marcações localizam-se em um par de cromossomos metacêntricos, enquanto no citótipo b em um acrocêntrico.

Cytogenetic characterization of two freshwater sciaenid species from the genus Plagioscion (P. squamosissimus and Plagioscion sp.) was obtained for the first time. Giemsa staining, Ag-NOR and C-banding revealed that both species presented 2n = 48 chromosomes (almost all acrocentric). Single NORs and heterochromatin were found mainly at the pericentromeric position. Karyotypic formulae and NOR location proved to be valuable in showing both interspecific and intraspecific differences. All chromosomes were acrocentric in P. squamosissimus. NORs were located at proximal positions on the long arms of the last chromosome pair of the complement, and were heteromorphic due to size differences. Such heteromorphic NORs seem to be associated with each population sampled. Plagioscion sp. presented two cytotypes: cytotype a (2M + 46A) and cytotype b (48A). In both cytotypes, NOR-bearing chromosomes were located at the proximal position on the long arms of the first chromosome pair of the complement. However, NOR-bearing chromosomes were metacentric in cytotype a and acrocentric in cytotype b.