RESUMO
The subfamily Triatominae (Hemiptera, Reduviidae) includes 150 species of blood-sucking insects, vectors of Chagas disease or American trypanosomiasis. Karyotypic information reveals a striking stability in the number of autosomes. However, this group shows substantial variability in genome size, the amount and distribution of C-heterochromatin, and the chromosome positions of 45S rDNA clusters. Here, we analysed the karyotypes of 41 species from six different genera with C-fluorescence banding in order to evaluate the base-pair richness of heterochromatic regions. Our results show a high heterogeneity in the fluorescent staining of the heterochromatin in both autosomes and sex chromosomes, never reported before within an insect subfamily with holocentric chromosomes. This technique allows a clear discrimination of the heterochromatic regions classified as similar by C-banding, constituting a new chromosome marker with taxonomic and evolutionary significance. The diverse fluorescent patterns are likely due to the amplification of different repeated sequences, reflecting an unusual dynamic rearrangement in the genomes of this subfamily. Further, we discuss the evolution of these repeated sequences in both autosomes and sex chromosomes in species of Triatominae.
Assuntos
Animais , Cromossomos de Insetos/genética , Heterocromatina/genética , Insetos Vetores/genética , Triatominae/genética , Evolução Biológica , Doença de Chagas/transmissão , DNA Ribossômico/genética , Cariotipagem , RNA Ribossômico/genética , Triatominae/classificaçãoRESUMO
Os triatomíneos pertencem à ordem Hemiptera, subordem Heteroptera, família Reduviidae e subfamília Triatominae. Todas as 148 espécies são hematófagas estritas e potenciais vetoras do protozoário Trypanosoma cruzi, agente etiológico da doença de Chagas. Algumas espécies são extremamente semelhantes do ponto de vista morfológico, o que pode dificultar o trabalho dos programas de controle de vetores. Triatoma guazu e T. williami são consideradas como espécies irmãs e não podem ser diferenciadas por diferentes abordagens, como análises morfométricas, isoenzimáticas e cromossômicas. Assim, o presente trabalho analisou as células haplóides durante a espermiogênese, com o objetivo de auxiliar na diferenciação desses vetores. A análise das espermátides de T. guazu e T. williami permitiu diferenciá-los, pois T. williami apresentou apenas um filamento heteropicnótico nas espermátides iniciais que foi parcialmente mantido durante o alongamento celular e T. guazu apresentou dois filamentos heteropicnóticos periféricos que se uniram durante o alongamento celular, dando origem a uma espermátide alongada totalmente heteropicnótica. Assim, ressaltando a importância dessa ferramenta na diferenciação de espécies relacionadas. No entanto, sugerimos que cruzamentos híbridos experimentais devem ser realizados entre esses triatomíneos, com o intuito de confirmar o status específico desses insetos vetores da doença de Chagas.(AU)
Triatomines belong to the Hemiptera order, Heteroptera suborder, Reduviidae family and Triatominae subfamily. All the 148 species are haematophagous strict and potential vectors of the protozoan Trypanosoma cruzi, etiologic agent of Chagas disease. Some species are very similar from a point of view morphological, what can difficult the work of vector control programs. Triatoma guazu and T. williami are considered sister species and cannot be differentiated by many approaches such as morphological, isoenzyme and chromosome analysis. Thus, the present study examined the haploid cells during spermiogenesis, aiming to assist the differentiation of these vectors. The analysis of spermatids of T. guazu and T. williami allowed to differentiate them because T. williami presented only one heteropyknotic filament in the early spermatids which was partially maintained during cell elongation and T. guazu presented two peripheral heteropycnotic filaments that have joined during cell elongation, leading to a elongated spermatid fully heteropycnotic. Thus highlighting the importance of this tool in the differentiation of related species. However, we suggest that experimental hybrid crosses should be made between these triatomines, in order to confirm the specific status of these insect vectors of Chagas disease.(AU)
Assuntos
Animais , Espermatogênese/genética , Doença de Chagas , Citogenética/métodos , Insetos Vetores , Triatoma/classificação , Triatominae/genéticaRESUMO
A pseudogene, designated as "ps(5.8S+ITS-2)", paralogous to the 5.8S gene and internal transcribed spacer (ITS)-2 of the nuclear ribosomal DNA (rDNA), has been recently found in many triatomine species distributed throughout North America, Central America and northern South America. Among characteristics used as criteria for pseudogene verification, secondary structures and free energy are highlighted, showing a lower fit between minimum free energy, partition function and centroid structures, although in given cases the fit only appeared to be slightly lower. The unique characteristics of "ps(5.8S+ITS-2)" as a processed or retrotransposed pseudogenic unit of the ghost type are reviewed, with emphasis on its potential functionality compared to the functionality of genes and spacers of the normal rDNA operon. Besides the technical problem of the risk for erroneous sequence results, the usefulness of "ps(5.8S+ITS-2)" for specimen classification, phylogenetic analyses and systematic/taxonomic studies should be highlighted, based on consistence and retention index values, which in pseudogenic sequence trees were higher than in functional sequence trees. Additionally, intraindividual, interpopulational and interspecific differences in pseudogene amount and the fact that it is a pseudogene in the nuclear rDNA suggests a potential relationships with fitness, behaviour and adaptability of triatomine vectors and consequently its potential utility in Chagas disease epidemiology and control.
Assuntos
Animais , DNA Espaçador Ribossômico/genética , Insetos Vetores/genética , Pseudogenes , Triatominae/genética , Doença de Chagas/transmissão , Genes de Insetos/genética , Insetos Vetores/classificação , Filogenia , Alinhamento de Sequência , Análise de Sequência de DNA , Triatominae/classificaçãoRESUMO
A doença de Chagas é considerada endêmica na América Latina, sendo uma das parasitoses com maior impacto socioeconômico nessa região. [...] A região do Vale do Rio Jaguaribe é considerada endêmica por apresentar tanto o ciclo doméstico quanto opara doméstico [...]. Com intuito de investigar a infestação pelos vetores da endemia chagásica, a circulação de Trypanosoma cruzi, bem como fornecer subsídios para o controle desses vetores, localidades rurais do município de Russas-CE foram selecionadas como área de estudo. Teve-se como objetivo analisar a fauna de triatomíneos e investigar os fatores associados ao risco de infestação por esses insetos e de transmissão da doença de Chagas em diferentes localidades rurais do município, através de indicadores entomológicos e domésticos, e utilizando técnicas de geoprocessamento. A busca pelos vetores foi realizada em novembro e dezembro de 2013, no intra e peridomicílio de 193 unidades domiciliares (UDs) das localidades rurais de Bonhu, Capim Grosso, Patos do Tito, Riacho do Barro,Sítio Maxixe e Timbaúba do Pitingão. Foram capturados 374 triatomíneos, sendo T. brasiliensis aespécie mais abundante (86,63 por cento), seguida por T. pseudomaculata (10,70 por cento) e Rhodnius nasutus(2,67 por cento). As infestações ocorreram majoritariamente no peridomicílio, mais precisamente em poleiros (7,46 por cento), amontoados de madeiras (6,16 por cento), currais de ovelhas/cabras (4,76 por cento),galinheiros (4,26 por cento), amontoados de telhas (3,84 por cento) e em casa de taipa abandonada, utilizada como abrigo de aves domésticas (1,21 por cento); em apenas um domicílio foi encontrado triatomíneo dentro da casa...
Endemic in Latin America, Chagas disease is one of the parasitic diseases with higher socioeconomic impact inthis region. [...] The Jaguaribe River Valley region is considered endemic since both domestic and peridomesticcycle are present [...]. In order to investigate the Chagasdisease vector infestation, Trypanosoma cruzi circulation, as well as to provide subsidies for vector control, six rurallocalities of the Russas municipality, Ceará, were selected as study area. Our aim was to analyze the triatominefauna and to investigate the factors associated with the triatomine infestation risk and Chagas disease transmissionin those localities, through the analysis of entomological and domestic indicators and the use of GeographicInformation System (GIS) techniques. Captures were carried out in November and December 2013, in intra andperidomestic environments of 193 housing units of the localities Bonhu, Capim Grosso, Patos do Tito, Riacho doBarro, Sítio Maxixe and Timbaúba do Pitingão. Three hundred seventy four triatomines were captured; T.brasiliensis (86.63 percent) was the most abundant species, followed by T. pseudomaculata (10.70 percent) and Rhodniusnasutus (2.67 percent). The infestations occurred mostly in the peridomicile, more precisely in perches (7.46 percent), woodpiles (6.16 percent), goat/sheap corrals (4.76 percent), chicken coop (4.26 percent), tile piles (3.84 percent) and an abandoned mud housethat was used as a poultry shelter (1.21 percent); only in one house was found triatomine in intradomicile...
Assuntos
Humanos , Doença de Chagas , Mapeamento Geográfico , Triatominae/genética , Controle de Vetores de Doenças , Reação em Cadeia da PolimeraseRESUMO
A doença de Chagas constitui um grande problema de saúde pública em diversospaíses da América Latina. Atualmente, estima-se que 6 a 7 milhões de pessoasestejam infectadas e 75 a 90 milhões estejam expostas à doença. O Trypanosomacruzi, seu agente etiológico, é representado por um conjunto de populações quecirculam em hospedeiros mamíferos e insetos vetores, apresentando grandeheterogeneidade de comportamento biológico e variações na sensibilidade a drogase prognóstico da doença. Assim, um grande desafio vem sendo identificarmarcadores genéticos dos isolados capazes de reuni-los em grupos discretos,visando sua caracterização do ponto de vista epidemiológico e de patogenia. Nestetrabalho, utilizamos metodologias baseadas em PCR convencional e PCR emTempo Real (qPCR) para realizar a quantificação da carga parasitária e tipagemmolecular do parasito diretamente de amostras sanguíneas de pacientes portadoresda doença de Chagas crônica. Para isso, foram selecionados 65 pacientes comsorologia positiva para T. cruzi, apresentando ou não a forma cardíaca da doença, e92 indivíduos com sorologia negativa, todos atendidos no ambulatório do InstitutoNacional de Infectologia Evandro Chagas, provenientes de diferentes regiões doBrasil. As amostras foram coletadas antes de qualquer tratamento e codificadas,para a realização de um estudo simples cego. A extração de DNA foi realizada apartir das amostras de sangue preservadas em Guanidina-EDTA, seguida daquantificação da carga parasitária por qPCR, em uma reação em multiplex, com umalvo para o DNA nuclear satélite de T. cruzi e um alvo para o gene da RNAse Phumana, como um controle interno...
Chagas disease is a major public health problem in many Latin American countries.Currently, an estimated 6 to 7 million people are infected and 75 million to 90 millionare exposed to the disease. Trypanosoma cruzi, the etiological agent is representedby a set of populations which circulate in mammalian hosts and insect vectors,presenting highly heterogeneous biological behavior as well as changes in drugsensitivity and prognosis of the disease. Thus, a major challenge is to identify geneticmarkers of isolates able to bring them into discrete groups, for their characterizationfrom an epidemiological point of view and pathogenesis. In this study, we usedconventional PCR based methodologies and Real-Time PCR (qPCR) to perform thequantification of parasite load and molecular typing of the parasite directly from bloodsamples of patients with chronic Chagas disease. Therefore, we selected 65 patientswith positive serology for T. cruzi, with cardiac symptons or not, and 92 with negativeserology, all of them were patients from National Institute of Infectology EvandroChagas (INI), from different regions of Brazil. The samples were collected prior to anytreatment and codified for realization of a single-blind study. DNA extraction wastaken from blood samples preserved in Guanidine-EDTA, followed by quantificationof the parasite load by qPCR, in a multiplex reaction, with a target for nuclear satelliteDNA of T. cruzi and a target for human RNAse P gene, as an internal control. Fromthe 157 patients, 64 proved positive by qPCR...
Assuntos
Humanos , Doença de Chagas/epidemiologia , Tipagem Molecular , Triatominae/genética , Reação em Cadeia da PolimeraseRESUMO
Triatoma melanocephalae T. lentisão espécies crípticas de triatomíneos pertencentes ao subcomplexo Brasiliensis. Esses organismos foram agrupados no subcomplexo apenas por caracteres morfológicos e pela disposição geográfica. Sendo assim, estudos citogenéticos são considerados como importantes ferramentas na classificação dos triatomíneos e, com isso, podem auxiliar na criação de um plano de profilaxia da doença. Por meio da técnica citogenética de impregnação por íons prata, foi possível visualizar a atividade nucleolar e as Regiões Organizadoras Nucleolares (RONs) desses insetos. T. melanocephala apresentou três RONs ativas nos autossomos durante a prófase I. T. lenti apresentou duas RONs ativas nos autossomos durante a prófase I e a metáfase I. Ambas as espécies apresentaram o fenômeno de persistência do material nucleolar encontrado em triatomíneos. Sendo assim, por meio da análise das RONs, foi possível observar que T. lenti, quando comparado com os outros organismos do subcomplexo, apresentou marcações semelhantes à T. tibiamaculata e que T. melanocephala não apresenta nenhuma relação direta com o subcomplexo.
Triatoma melanocephala and T. lenti are important vectors of Chagas disease. These cryptic species of triatomines are grouped in the subcomplex brasiliensis due only to morphological characters and geographical distribution. Cytogenetic studies are important to the classification of insects and can assist in creating a disease prevention plan. The aim of the present study was to determine nucleolar activity and nucleolus organizer regions (NORs) in these insects using the cytogenetic method of silver ion impregnation. T. melanocephala exhibited three active NORs in autosomes during prophase I. T. lentiexhibited two active NORs in autosomes during prophase I and metaphase I. Both species exhibit the persistent nucleolar material found in triatomines. The analysis of NORs in the present study revealed that T. lentiexhibited labeling similar to that found in T. tibiamaculata, which belongs to the subcomplex, whereas T. melanocephala shows no direct relationship with the subcomplex.
Assuntos
Análise Citogenética , Classificação/métodos , Triatominae/citologia , Triatominae/genética , Doença de Chagas , Vetores de DoençasRESUMO
In this study, we used fluorescence in situ hybridisation to determine the chromosomal location of 45S rDNA clusters in 10 species of the tribe Rhodniini (Hemiptera: Reduviidae: Triatominae). The results showed striking inter and intraspecific variability, with the location of the rDNA clusters restricted to sex chromosomes with two patterns: either on one (X chromosome) or both sex chromosomes (X and Y chromosomes). This variation occurs within a genus that has an unchanging diploid chromosome number (2n = 22, including 20 autosomes and 2 sex chromosomes) and a similar chromosome size and genomic DNA content, reflecting a genome dynamic not revealed by these chromosome traits. The rDNA variation in closely related species and the intraspecific polymorphism in Rhodnius ecuadoriensis suggested that the chromosomal position of rDNA clusters might be a useful marker to identify recently diverged species or populations. We discuss the ancestral position of ribosomal genes in the tribe Rhodniini and the possible mechanisms involved in the variation of the rDNA clusters, including the loss of rDNA loci on the Y chromosome, transposition and ectopic pairing. The last two processes involve chromosomal exchanges between both sex chromosomes, in contrast to the widely accepted idea that the achiasmatic sex chromosomes of Heteroptera do not interchange sequences.
Assuntos
Animais , Feminino , Masculino , Cromossomos de Insetos/genética , DNA Ribossômico/genética , /genética , Triatominae/genética , Cromossomo X/genética , Cromossomo Y/genética , Evolução Biológica , Diploide , Hibridização in Situ Fluorescente , Cariotipagem , Especificidade da EspécieRESUMO
Triatomines have been important model organisms for behavioural research. Diverse reports about triatomine host search, pheromone communication in the sexual, shelter and alarm contexts, daily cycles of activity, refuge choice and behavioural plasticity have been published in the last two decades. In recent times, a variety of molecular genetics techniques has allowed researchers to investigate elaborate and complex questions about the genetic bases of the physiology of insects. This, together with the current characterisation of the genome sequence of Rhodnius prolixus allows the resurgence of this excellent insect physiology model in the omics era. In the present revision, we suggest that studying the molecular basis of behaviour and sensory ecology in triatomines will promote a deeper understanding of fundamental aspects of insect and, particularly, vector biology. This will allow uncovering unknown features of essential insect physiology questions for a hemimetabolous model organism, promoting more robust comparative studies of insect sensory function and cognition.
Assuntos
Animais , Comportamento Animal/fisiologia , Genoma de Inseto/genética , Insetos Vetores/genética , Triatominae/genética , Relógios Circadianos/genética , Ritmo Circadiano/genética , Locomoção , Feromônios/genética , Rhodnius/genética , Navegação EspacialRESUMO
In the present study, the morphology, color pattern, chromosomal complement and aspects of meiosis in natural populations at the borders of the distributions of Mepraia gajardoi Frías et al and Mepraia spinolai (Porter) are described. The males of these bordering populations are brachypterous or macropterous, while females are always micropterous. Morphological and cytogenetic data indicated that the populations that border the distributions of M. gajardoi and M. spinolai, belong to a different species of parapatric origin.
Assuntos
Animais , Feminino , Masculino , Triatominae/classificação , Triatominae/genética , Chile , Cariotipagem , Triatominae/anatomia & histologiaRESUMO
In seven studied communities of Western Mexico, triatomine specimens were sympatrically collected, some with atypical morphological characteristics in contrast to pure specimens, which were presumed to be hybrids. More than 200 specimens of Meccus pallidipennis and Meccus longipennis with brown-yellow markings on dorsal connexival segments were collected in Ahuacapán and Quitupan. In La Mesa, more than 60 specimens similar to Meccus picturatus in most morphological characteristics (including size) were collected, although they presented a largely yellowish corium like M. pallidipennis. Interfertility was proven between all of the studied wild hybrid specimens, as well as between all the experimental laboratory hybrids. Two different phenotypes (M. picturatus and M. longipennis) were obtained from crosses between M. picturatus x M. picturatus and M. longipennis x M. longipennis from the three studied localities in state of Nayarit as from La Mesita. Results support the hypothesis that the subspecific ranking of those triatomines may, therefore, be more appropriate because reproductive isolation has not been developed and complete interbreeding was recorded.
Assuntos
Animais , Feminino , Masculino , Cruzamentos Genéticos , Triatominae/genética , Quimera/genética , México , Fenótipo , Reprodução/fisiologia , Triatominae/classificação , Triatominae/fisiologiaRESUMO
Nucleotide sequences of mitocondrial 16S rDNA gene were analyzed in 14 populations of triatomine bugs from colonies maintained by SESA, Araraquara, São Paulo, Brazil, comparing them with sequences of same gene found in the GenBank. The fragments varied from 311 to 317 bp, with low intra-specific genetic distance (0 percent to 0.6 percent), with exception of the relationship among Triatoma sordida specimens (1 percent) and T. brasiliensis specimens (1.3 percent) that were attributed to different geographical populations. The paraphily of Rhodniini and Panstrongylus genus was evidenced by this analyses, confirming previous results between these and the narrow relationships of R. prolixus with R. robustus and of T. infestans with T. platensis. The relationship between T. maculata and T. pseudomaculata has not been resolved, since these taxa appeared both in monophyly and as in paraphyly: T. pseudomaculata (SESA) is grouped with T. maculata (sequence of GenBank) and the associated T. brasiliensis (SESA), while T. maculata (SESA) appears grouped with T. pseudomaculata of SESA and GenBank. The results evidence the utility of the gene 16S as molecular marker in the species of triatomine bugs and its importance in systematic and taxonomy questions. There is a necessity of new studies including new molecular markers associated with classic systematic characters of morphology, ecology and behavior to adjust systematic decisions since those will be not of only systematic impact but, for new strategies of control.
Foram analisadas seqüências de nucleotídeos do gene 16S do rDNA mitocondrial em 14 populações de triatomíneos mantidos em colônias no insetário SESA de Araraquara- SP, comparando-as com seqüências do mesmo gene disponíveis no GenBank. Os fragmentos variaram de 311 a 317 pb com baixa variação intra-específica entre as distâncias genéticas (0 por cento a 0,6 por cento), exceto para os relacionamentos entre espécimes de Triatoma sordida (1 por cento) e espécimes de T. brasiliensis (1,3 por cento) atribuídos a populações geográficas diferentes. A parafilia de Rhodniini e do gênero Panstrongylus foi evidenciada pelas analises, confirmando resultados anteriores entre estes e os estreitos relacionamentos de R. prolixus com R. robustus e de T. infestans e T. platensis. O relacionamento entre T. maculata e T. pseudomaculata não foi solucionado, uma vez que, esses táxons apareceram tanto em monofilia quanto em parafilia: T. pseudomaculata (SESA) está agrupado com T. maculata (seqüência do GenBank) e associados a T . brasiliensis (SESA), enquanto T. maculata (SESA) aparece agrupado com T. pseudomaculata do SESA e do GenBank. Os resultados evidenciam a utilidade do gene 16S como marcador de espécies de triatomíneos e sua importância em questões de sistemática e taxonomia. Há necessidade de novos estudos envolvendo outros marcadores associados a caracteres sistemáticos clássicos de morfologia, ecologia e comportamento para decisões sistemáticas adequadas uma vez, que teriam impacto não apenas sistemático mas, para as estratégias de controle.
Assuntos
Animais , Doença de Chagas , DNA , Insetos Vetores , Triatominae/genéticaRESUMO
The present work is a thorough investigation of the degree of reproductive isolation between Meccus mazzottii and Meccus longipennis, Meccus picturatus, Meccus pallidipennis and Meccus bassolsae, as well as between M. longipennis and M. picturatus. We examined fertility and segregation of morphological characteristics in two generations of hybrids derived from crosses between these species. The percentage of pairs with (fertile) offspring was highest in the set of crosses between M. longipennis and M. picturatus, and lowest between M. mazzottii and M. picturatus. Most first-generation (F1) individuals from crosses involving M. mazzottii were morphologically similar to this species, while only F1 x F1 progeny of parental crosses between M. mazzottii and M. longipennis had offspring second generation that looked like M. mazzottii. The results indicate that different degrees of reproductive isolation apparently exist among the species of the Phyllosoma complex examined in this study. The biological evidence obtained in this study does not support the proposal that M. longipennis and M. picturatus are full species. It could indicate on the contrary, that both could be considered as subspecies of a single polytypic species. On the other hand, biological evidence supports the proposal that M. mazzottii is a full species.
Assuntos
Animais , Feminino , Masculino , Cruzamentos Genéticos , Quimera/genética , Triatominae/genética , México , Fenótipo , Reprodução/fisiologia , Triatominae/classificação , Triatominae/fisiologiaRESUMO
Triatomines are vectors of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. These hematophagous insects belong to the order Heteroptera and to the family Reduviidae. Disseminated throughout large portions of Brazil and of other Latin American countries, Chagas disease is a serious and important public health problem that is difficult to treat. Cytogenetically, the interest in triatomines is in its holocentric chromosomes and in its uncommon meiosis process; sexual segregation is post-reductional. The basic number of chromosomes in triatomines is 2n = 22. We analyzed spermatogenesis in Triatoma maculata and T. pseudomaculata, with emphasis on the following aspects: spermatogenesis phases, chromatin and meiotic chromosome structure and the nucleolar cycle. These species are found principally in northeastern Brazil and are potential vectors for T. cruzi. The specimens were supplied by the insectary of the Special Health Service of Araraquara (SESA), Department of Epidemiology, School of Public Health, University of São Paulo. Cells were obtained from the testicles of adult males; after crushing they were submitted to the following cytochemical techniques: lacto-acetic orcein staining, impregnation with silver ions, C-banding and critical electrolyte concentrations. An association was observed between the nucleolus and heterochromatic regions, in both interphasic somatic cells and germ line. The localization of these specific regions also demonstrated an intimate functional relationship between these structures. The karyograms of the two species, mounted at metaphase I, indicated 10 autosomes and one pair of sexual chromosomes (22 chromosomes), coinciding with the modal number for the group. With C-banding, the Y chromosome is heterochromatic in both species...
Assuntos
Análise Citogenética , Triatominae/genética , InsetosRESUMO
An ecological-evolutionary classification of Amazonian triatomines is proposed based on a revision of their main contemporary biogeographical patterns. Truly Amazonian triatomines include the Rhodniini, the Cavernicolini, and perhaps Eratyrus and some Bolboderini. The tribe Rhodniini comprises two major lineages (pictipes and robustus). The former gave rise to trans-Andean (pallescens) and Amazonian (pictipes) species groups, while the latter diversified within Amazonia (robustus group) and radiated to neighbouring ecoregions (Orinoco, Cerrado-Caatinga-Chaco, and Atlantic Forest). Three widely distributed Panstrongylus species probably occupied Amazonia secondarily, while a few Triatoma species include Amazonian populations that occur only in the fringes of the region. T. maculata probably represents a vicariant subset isolated from its parental lineage in the Caatinga-Cerrado system when moist forests closed a dry trans-Amazonian corridor. These diverse Amazonian triatomines display different degrees of synanthropism, defining a behavioural gradient from household invasion by adult triatomines to the stable colonisation of artificial structures. Anthropogenic ecological disturbance (driven by deforestation) is probably crucial in the onset of the process, but the fact that only a small fraction of species effectively colonises artificial environments suggests a role for evolution at the end of the gradient. Domestic infestation foci are restricted to drier subregions within Amazonia; thus, populations adapted to extremely humid rainforest microclimates may have limited chances of successfully colonising the slightly drier artificial microenvironments. These observations suggest several research avenues, from the use of climate data to map risk areas to the assessment of the synanthropic potential of individual vector species.
Assuntos
Animais , Humanos , Evolução Biológica , Doença de Chagas/epidemiologia , Insetos Vetores/classificação , Trypanosoma cruzi , Triatominae/classificação , Doença de Chagas/transmissão , Geografia , Insetos Vetores/genética , Insetos Vetores/parasitologia , Filogenia , América do Sul/epidemiologia , Triatominae/genética , Triatominae/parasitologiaRESUMO
A comparative study of holocentric chromosomes in the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans was carried out in order to characterize heterochromatin, rDNA active sites and nucleolar proteins. Cytological preparations of seminiferous tubules were stained by silver impregnation, C banding, fluorochromes cma3/da and dapi/da, and fluorescent in situ hybridization (FISH) with Drosophila melanogaster 28S rDNA probe. Our results showed interesting aspects of the organization of chromatin and chromosomes in the meiotic cells of these insects. In R. pallescens, sex chromosomes (X, Y) were distinct from autosomes, when submitted to silver impregnation, C banding, CMA3 staining, and FISH, confirming that these chromosomes bear nucleolar organizer regions (NORs). In P. megistus, two of the three sex chromosomes were CMA3/DAPI-; at early meiotic prophase and at diakinesis, silver impregnation corresponded with FISH signals, indicating that in this species, two chromosomes (probably a sex chromosome and an autosome) bear NORs. In T. infestans, silver nitrate and FISH also stained corresponding areas on meiotic chromosomes. Our data suggest that in triatomines, in general, the number and location of NORs are species-specific. These regions may be considered important chromosome markers for comparative studies to improve the understanding of evolutionary mechanisms in these hematophagous insects.
Assuntos
Animais , Masculino , Coloração e Rotulagem/métodos , Cromossomos/metabolismo , Hibridização in Situ Fluorescente/métodos , Triatominae/genética , Panstrongylus/genética , Rhodnius/genética , Triatoma/genética , Túbulos Seminíferos/citologiaRESUMO
Os triatomíneos são insetos pertencentes à ordem Hemiptera, subordem Heteroptera, família Reduviidae e subfamília Triatominae. Todos os membros desta subfamília são hematófagos. Os triatomíneos surgiram a partir de reduvídeos predadores e provavelmente têm origem polifilética. A combinação dos fatores anatômicos, fisiológicos e etológicos presentes no grupo, bem como os caracteres plésio e apomórficos que diferenciam as cinco tribos e os quatorze gêneros de triatomíneos reforçam a hipótese polifilética. As tribos Rhodniini, Cavernicolini, Bolboderini, Linshcosteini e Alberproseniini constituem grupos monofiléticos, per si, enquanto a tribo Triatomini é considerada polifilética. O Novo Mundo é claramente o centro de diversidade dos triatomíneos e possivelmente é a região de sua origem. Entre as aproximadamente 129 espécies desses insetos, 105 ocorrem somente nas Américas. Atualmente, os triatomíneos são considerados um grupo polifilético, definido com base em seus caracteres apomórficos convergentes relacionados à hematofagia. Acredita-se que este hábito alimentar tenha surgido várias vezes nos Reduviidae durante sua evolução. O presente trabalho faz uma revisão sobre a filogenia destes vetores da Doença de Chagas, aborda tópicos como a origem da hematofagia nos triatomíneos e ancestralidade proposta para o grupo.
Assuntos
Animais , Insetos Vetores/classificação , Filogenia , Triatominae/classificação , Doença de Chagas/transmissão , Insetos Vetores/genética , Triatominae/genéticaRESUMO
Programas destinados ao controle da doença de Chagas vêm apresentando resultados positivos. Estudos moleculares têm auxiliado programas de controle exitosos através da identificação e caracterização de populações de vetores introduzidas, além da definição precisa das espécies a serem combatidas. Contudo, pesquisadores e autoridades da área de saúde estão enfrentando novos desafios, no âmbito da América Latina. Vetores nativos estão continuadamente re-infestando habitações previamente tratadas com inseticidas, e triatomíneos silvestres estão mantendo ciclos de transmissão da doença em regiões de floresta tropical úmida (incluíndo a Amazônia), sem colonizar habitações humanas. Nessas situações, estudos detalhados dos vetores são essenciais na definição de padrões de risco epidemiológico e no esclarecimento do envolvimento de espécies de triatomíneos pouco conhecidas, na transmissão da doença. Investigações eco-epidemiológicas dessa natureza, assim como o planejamento e monitoramento de intervenções de controle, dependem fortemente de identificações taxonômicas precisas. Problemas decorrentes de especiação críptica e da plasticidade fenotípica, ilustram essa necessidade - e de como a sistemática molecular pode contribuir na geração das respostas necessárias. A análise de dados moleculares também auxilia no entendimento de aspectos básicos da evolução e tendências adaptativas dos vetores. Neste artigo, fazemos uma revisão da aplicação de marcadores moleculares (concentrando em isoenzimas e sequenciamento de ADN) no estudo de triatomíneos. Analisamos também a aplicabilidade, vantagens e desvantagens dos métodos mais utilizados, nas investigações em diferentes níveis sistemáticos (populações, espécies e categorias taxonômicas mais elevadas).
Assuntos
Animais , Humanos , Doença de Chagas , Técnicas Genéticas , Insetos Vetores/genética , Triatominae/genética , Doença de Chagas/prevenção & controle , Doença de Chagas/transmissão , Insetos Vetores/classificação , Triatominae/classificaçãoRESUMO
Chromatin organization in the holocentric chromosomes of three triatomines species was cytologically studied by fluorescent in situ hybridization with a 45S rDNA probe of Drosophila melanogaster to localize ribosomal genes. In Triatoma tibiamaculata, metaphases I showed telomeric highlights in a single, larger bivalent. In T. protacta, hybridization was detected in one of the telomeres of an autosomal chromosome. In T. platensis, there were highlights in a single, smaller chromosome (X chromosome). The results obtained did not agree with the expected localization of rDNA genes in the sex chromosomes of triatomines, as demonstrated by silver impregnation, and suggest that the chromosome reorganization that occurred in this group during evolution may be a more important mechanism involved in rDNA distribution.
Assuntos
Animais , Masculino , Cromossomos/genética , DNA Ribossômico/análise , Triatominae/genética , Hibridização in Situ Fluorescente , Bandeamento Cromossômico , DNA Ribossômico/genética , Especificidade da Espécie , Fatores do Domínio POU , Metáfase , Proteínas de Drosophila , Proteínas de Homeodomínio , Região Organizadora do Nucléolo , Triatominae/classificaçãoRESUMO
The authors describe a new species of Triatominae (Hemiptera, Reduviidae) from the State of Rio Grande do Sul, Brazil. The study was made with specimens captured in basaltic formations, at an average altitude of 750 m.o.s.l. The new species is included in the oliveirai complex together with other four species T. williami, T. matogrossensis, T. guazu and T. jurbergi). The new species was compared with the most similar one, T. oliveirai, from which the main differences are on the proportions of head, ante and postocular regions, the general color pattern and the male genitalia, specially on the median process of the pygophore, the support of phallosome, the vesica and the process of the endosome
Assuntos
Animais , Masculino , Feminino , Triatominae/classificação , Brasil , Diferenciação Sexual , Triatominae/anatomia & histologia , Triatominae/genéticaRESUMO
The evolutionary history and times of divergence of triatomine bug lineages are estimated from molecular clocks inferred from nucleotide sequences of the small subunit SSU (18S) and the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA of these reduviids. The 18S rDNA molecular clock rate in Triatominae, and Prosorrhynchan Hemiptera in general, appears to be of 1.8 per cent per 100 million years (my). The ITS-2 molecular clock rate in Triatominae is estimated to be around 0.4-1 per cent per 1 my, indicating that ITS-2 evolves 23-55 times faster than 18S rDNA. Inferred chronological data about the evolution of Triatominae fit well with current hypotheses on their evolutionary histories, but suggest reconsideration of the current taxonomy of North American species complexes.