RESUMO
The subfamily Triatominae (Hemiptera-Reduviidae) includes more than 150 blood-sucking species, potential vectors of the protozoan Trypanosoma cruzi, causative agent of Chagas disease. A distinctive cytogenetic characteristic of this group is the presence of extremely stable chromosome numbers. Unexpectedly, the analyses of the chromosomal location of ribosomal gene clusters and other repetitive sequences place Triatominae as a significantly diverse hemipteran subfamily. Here, we advance the understanding of Triatominae chromosomal evolution through the analysis of the 45S rDNA cluster chromosomal location in 92 Triatominae species. We found the 45S rDNA clusters in one to four loci per haploid genome with different chromosomal patterns: On one or two autosomes, on one, two or three sex chromosomes, on the X chromosome plus one to three autosomes. The movement of 45S rDNA clusters is discussed in an evolutionary context. Our results illustrate that rDNA mobility has been relatively common in the past and in recent evolutionary history of the group. The high frequency of rDNA patterns involving autosomes and sex chromosomes among closely related species could affect genetic recombination and the viability of hybrid populations, which suggests that the mobility of rDNA clusters could be a driver of species diversification.
Assuntos
Doença de Chagas , Reduviidae , Triatominae , Animais , Doença de Chagas/veterinária , Cromossomos , DNA Ribossômico/genética , Triatominae/genéticaAssuntos
Animais , Rhodnius/classificação , Rhodnius/citologia , Rhodnius/genética , Cariótipo , América do Sul , CariotipagemAssuntos
Animais , Panstrongylus/classificação , Panstrongylus/genética , Cromossomos , Biodiversidade , CariotipagemRESUMO
In this study, the karyometry of different Triatoma infestans populations from different states of Brazil was analyzed and compared with those of a population from Cochabamba. No significant differences were found between the population from Cochabamba and those from Brazil. These results are consistent with the origin of the T. infestans populations of Brazil by a founder effect from Cochabamba. Moreover, these findings also confirm that a founder effect occurred during the dispersal of T. infestans populations in different Brazilian states.
Assuntos
Doença de Chagas/transmissão , Cromossomos de Insetos/química , Efeito Fundador , Insetos Vetores/genética , Triatoma/genética , Distribuição Animal , Animais , Brasil/epidemiologia , Doença de Chagas/epidemiologia , Doença de Chagas/parasitologia , Colômbia/epidemiologia , Humanos , Insetos Vetores/classificação , Cariotipagem , Filogeografia , Triatoma/classificação , Trypanosoma cruzi/patogenicidade , Trypanosoma cruzi/fisiologiaRESUMO
This paper reports on the first occurrence of Psammolestes tertius in the Chapada Diamantina region, located in the city of Seabra, Bahia State, in northeastern Brazil. Following an active search, 24 P. tertius specimens were collected from Phacellodomus rufifrons (rufous-fronted thornbird) nests. The insects did not present any symptoms of infection by Trypanosoma cruzi. P. tertius males were cytogenetically analyzed, and the results were compared with those of other specimens from the Brazilian State of Ceará. Triatomines from both locations presented the same cytogenetic characteristics: 22 chromosomes, little variation in the size of the autosomes, Y chromosomes that were larger than the X chromosomes, a chromocenter formed only by the sex chromosomes during prophase, and autosomes lacking constitutive heterochromatin. However, it is important to note that this species shows intraspecific chromosomal variation. In light of the results obtained, it is recommended that more studies be performed to characterize P. tertius. These studies will be particularly helpful in understanding this species in ecological, biological, biogeographical, and phylogenetic terms.
Assuntos
Cromossomos de Insetos/ultraestrutura , Variação Genética , Triatominae/genética , Animais , Cromossomos de Insetos/genética , Heterocromatina/ultraestrutura , Masculino , Triatominae/classificação , Triatominae/citologiaRESUMO
In addition to the epidemiological importance regarding the transmission of Chagas disease, triatomines are also important biological models for cellular studies, because they have holocentric chromosomes, post-reductional meiosis for sex chromosomes, and nucleolar persistence. Although the nucleolus is present during spermiogenesis, it was suggested that it is inactivated and all transcriptional activity necessary for cell differentiation is supported by the chromatoid body (CB). Thus, considering the importance of CB to triatomine spermatogenesis, this paper aims to analyze the presence of this organelle in the Rhodnius genus. The testicles of five adult R. neglectus and R. prolixus males were analyzed after semi-fine sections were performed, and the material was subjected to silver ion impregnation. The CB organelle was found in the spermatid of both species. Most CB studies focused on the Triatoma genus. This study described the existence of CB in Rhodnius, confirming thus the importance of this cytoplasmic organelle to spermiogenesis of these insect vectors of Chagas disease.
Assuntos
Cromossomos de Insetos/genética , Rhodnius/citologia , Espermátides/citologia , Animais , Masculino , Rhodnius/genética , Espermátides/metabolismo , Espermatogênese , Testículo/metabolismoRESUMO
The tribe Rhodniini is a monophyletic group composed of 22 species, with 19 in the Rhodnius genus and three in the Psammolestes genus. These insects are morphologically very similar (cryptic species), and new tools are important for investigating the taxonomy of these vectors. Spermiotaxonomy is an important tool in differentiating between related species, and this study analyzed the spermatids of Rhodniini species to elucidate their spermiotaxonomy. All of the Rhodniini species contained two heteropyknotic filaments in the extremities of their cells. Although spermiotaxonomy has been an important tool in differentiating between species of the Triatoma genus, all of the species in the Rhodnius genus exhibited the same characteristics in their male gametes. However, spermatid analysis made it possible to confirm the monophyly of the Rhodniini tribe, because Psammolestes tertius had the same pattern as that described for Rhodnius. The results of this study demonstrate that spermiotaxonomy, in addition to being an important tool for differentiating between related species of Triatoma, can be used as an optimization tool in phylogenetic analyses.
Assuntos
Rhodnius/classificação , Rhodnius/genética , Animais , Masculino , Filogenia , Triatominae/classificação , Triatominae/genéticaRESUMO
The Brasiliensis subcomplex is a monophyletic group formed by the species Triatoma brasiliensis brasiliensis, T. b. macromelasoma, T. juazeirensis, T. melanica, and T. sherlocki. However, using cytogenetic data and experimental hybrid crosses, T. lenti and T. petrochiae were also grouped into this subcomplex. This study aims to analyze the properties of hotspot in the D2 domain of the nuclear gene 28S in all species of the Brasiliensis subcomplex as well as T. lenti and T. petrochiae. These species show two transversions at position 385 (GâC and TâG). We suggest that this mutation in haplotype 4 may be an initial molecular tool that supports the relationship of these species with the subcomplex. In addition to the transversion at haplotype 4, these species, aside from T. melanica, also possess a transversion at position 385 (GâT) in haplotype 1. Thus, we describe the hotspot mutations of the D2 domain of the nuclear gene 28S for species in Brasiliensis subcomplex as follows: three transversions are present at position 385 of haplotypes 1 and 4, which are shared by members of the subcomplex as well as T. lenti and T. petrochiae. These transversions may be considered a synapomorphy between these species. However, we emphasize that new phylogenetic studies should be conducted to evaluate whether T. lenti and T. petrochiae are truly members of the Brasiliensis subcomplex.
Assuntos
Proteínas de Insetos/química , Proteínas de Insetos/metabolismo , Triatominae/genética , Triatominae/metabolismo , Animais , Haplótipos/genética , Proteínas de Insetos/genética , Filogenia , Triatominae/classificaçãoRESUMO
The Triatominae subfamily consists of 150 species in 18 genera, grouped into six tribes. In cytogenetics, triatomines are important biological models because they have holocentric chromosomes and nucleolar persistence in meiosis. The phenomenon of nucleolar persistence has been described for 23 species of triatomine in three genera: Triatoma, Rhodnius, and Panstrongylus. However, new species and genera should be analyzed to assess whether nucleolar persistence is a peculiarity of Triatominae. Thus, this study aimed to analyze nucleolar behavior during spermatogenesis of Meccus pallidipennis and M. longipennis, focusing on the nucleolar-persistence phenomenon. Through the analysis of spermatogenesis, more specifically of meiotic metaphase, we observed the phenomenon of nucleolar persistence in M. pallidipennis and M. longipennis, represented by remnants of nucleolar material in metaphase. Thus, although nucleologenesis of new species, and, especially, new genera, should be analyzed, this study confirms for the first time the phenomenon of nucleolar persistence in the genus Meccus. Therefore, we emphasize the importance of new studies in this area in order to assess whether this phenomenon is truly a synapomorphy of these hematophagous insects.