High chromosomal mobility of rDNA clusters in holocentric chromosomes of Triatominae, vectors of Chagas disease (Hemiptera-Reduviidae).

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.

Spermatogenesis in Nesotriatoma bruneri (Usinger 1944) (Hemiptera, Triatominae).

The Nesotriatoma genus consists of the species N. flavida N. bruneri and N. obscura, forming the Flavida complex. Variation in the size and morphological differences intraspecific of N. flavida led to the description of N. bruneri. Two years later, the same author proposed the synonymization of N. bruneri with N. flavida. Only in 1981 the specific status N. bruneri was recovered by means of morphological analysis of the genitalia. However, recently by genetic analysis, it was suggested that N. bruneri and N. flavida should be again synonymized. As Chagas disease has no cure, the main way to minimize the incidence of this disease is by vector control. Thus, grouping biological data from these hematophagous insects can assist in the development of vector control programs and mainly assist in taxonomic issues of synonymization. Thus, this paper describes spermatogenesis of N. bruneri. Three adult N. bruneri males were cytogenetically analyzed. The meiotic behavior observed for N. bruneri was very similar to that observed for the triatomine species with 23 chromosomes: during prophase, chromatin compaction was observed, the chromocenter composition was characterized (X1, X2 and Y), and the species karyotype was confirmed as 2n = 23 (20A + X1X2Y), as it was observed for N. flavida. Moreover, it was possible to observe anaphase and telophase. Thus, this study describes reproductive aspects of N. bruneri in order to contribute to the biological knowledge of these insects of epidemiological importance. Furthermore, this corroborates the synonymization of N. bruneri with N. flavida.

New chromosomal evidence for the origin of Triatoma infestans populations from Brazil.

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.

Alkaline phosphatase activity in salivary gland cells of Rhodnius neglectus and R. prolixus (Hemiptera, Triatominae).

Alkaline phosphatase activity was detected in salivary gland cells of the Rhodnius neglectus Lent, 1954, and R. prolixus Stal, 1859, vectors of Trypanosoma cruzi Chagas, 1909 (etiological agent of Chagas disease) and T. rangeli Tejera, 1920 (pathogenic to insect). The Gomori technique was used to demonstrate alkaline phosphatase activity. Alkaline phosphatase activity was observed throughout the entire gland, with an increased activity in the posterior region of the principal gland. In particular, phosphatase activity was found in the nucleolar corpuscles, suggesting a relationship with the rRNA transcription and ribosomal biogenesis. Alkaline phosphatase was also detected in the nuclear membrane and nuclear matrix, suggesting an association with the nucleo-cytoplasmic transport of ribonucleoproteins and the mechanisms of cell cycle and DNA replication, respectively. This study highlights the importance of alkaline phosphatase in the salivary gland of R. prolixus and R. neglectus and emphasizes its importance in secretory activity. Secretory activity is directly involved in hematophagy and, consequently, in development during metamorphosis. The observed presence of alkaline phosphatase suggests its involvement in the production of saliva allowing feeding of these insects that are important vectors of Chagas disease.

Description of the diploid chromosome set of Triatoma pintodiasi (Hemiptera, Triatominae).

Triatoma pintodiasi has been described and recently grouped in the Rubrovaria subcomplex. T. pintodiasi was initially compared to T. carcavalloi by staining and subsequently identified as T. circummaculata. However, after thorough examination, it was observed to be a cryptic species of T. circummaculata, and was described based on morphological features, morphometric data, and biochemical patterns of hemolymph. Thus, this paper aims to describe the karyotype of, and spermatogenesis in, T. pintodiasi, in order to elucidate the reproductive biology and taxonomy of the species. Sex chromosomes of T. pintodiasi formed a heteropyknotic chromocenter, and compaction of chromatin was observed during prophase. However, in contrast to observations in T. carcavalloi and T. circummaculata, in T. pintodiasi it was observed individualization of the sex chromosomes. The diploid chromosome set of the species 2n = 22 (20A + XY) is described through analysis of metaphases I and II. Initial cytogenetic characteristics of T. pintodiasi are described and the observed differences in the chromocenter are suggested as a possible cytotaxonomic tool. To gain a better understanding of the specific status of this cryptic species, however, we emphasize the need for further cytogenetic, molecular, biological, and biogeographical analysis, in addition to experimental hybrid crosses with other species of the Rubrovaria subcomplex.

Presence of chromatoid bodies in the Rhodnius genus detected by cytochemical analysis.

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.

Description of the pre-reductional sex chromosome during male meiosis of Pachylis laticornis (Heteroptera: Coreidae).

In Heteroptera, the division of sex chromosomes is well defined as post-reductional for most of species, i.e., the first meiotic division is equational and the second is reductional. However, in some species pre-reductional division has been observed, whereby the first meiotic division is reductional and the second is equational. These include Anisops fieberi (Notonectidae), Ectrychotes disparate (Reduviidae), Dictyonota tricornis (Tingidae), and Archimerus alternatus (Coreidae), as well as other species of the genus Pachylis, in the family Coreidae. Thus, this study aimed to characterize the meiotic behavior of Pachylis laticornis, in order to consider whether this species also undergoes pre-reduction division for the sex chromosomes. Cytogenetic analysis of meiosis in P. laticornis made it possible to characterize the holocentric nature of the chromosomes, the chromosome number of this species [2n = 15 (2m + 12A + X0)], the chromosomal system of sex X0 type, and the presence of m-chromosomes. Furthermore, the analysis of anaphase I, telophase I and II allowed pre-reductional meiotic behavior to be observed for this sex chromosome. Thus, this meiotic behavior was confirmed for another species of Heteroptera, stressing the importance of more cytogenetic studies of meiosis to increase our understanding of variation in the behavior of sex chromosomes during spermatogenesis in heteropterans. Therefore, the present study describes the chromosomal number, the system of sex determination, and meiotic behavior of P. laticornis, corroborating the relationship of this species with others of the same genus.

Cytochemical characteristics of blood cells from Brazilian tortoises (Testudines: Testudinidae).

The hematology of wild and captive animals is essential for obtaining details about species and represents a simple method of diagnosing disease and determining prognosis. Few studies have described the morphology of chelonian blood cells, which are more common in sea and freshwater turtle species. Thus, in order to further our understanding and recognition of different chelonian cells types, the present study aimed to describe blood cells from the two species of Brazilian tortoises, Chelonoidis carbonarius and C. denticulatus. Cytochemical analysis of tortoise blood tissue with Panótico®, made it possible to describe all the of the chelonian cell types (with the exception of thrombocytes): erythrocytes, agranular leukocytes (monocytes and lymphocytes), and granular leukocytes (eosinophils, heterophils, basophils, and azurophils). These data are of high importance for establishing hematological profiles of Brazilian tortoises and reptiles. Therefore, based on our results and on comparative analyses with data from the literature for other reptile species, we can conclude that the blood cells described for Brazilian tortoises are found in all species of reptiles that have been analyzed thus far, and may be characterized and used as a comparative parameter between different groups to evaluate the health status of these animals.

Spermiotaxonomy of the tribe Rhodniini (Hemiptera, Triatominae).

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.

Cytogenetic analysis of Triatoma pseudomaculata Corrêa and Espínola, 1964 (Hemiptera, Triatominae) from different Brazilian states.

Triatoma maculata and T. pseudomaculata are allopatric; however, it is believed that T. maculata was introduced into the Brazilian northeast by passive transportation of the nymphs between the feathers of migratory birds, followed by the speciation of T. pseudomaculata. T. pseudomaculata is the second most epidemiologically important species in the northeast of Brazil after T. brasiliensis. Therefore, given the broad range of T. pseudomaculata, the objective of the present study was to cytogenetically analyze different populations of T. pseudomaculata from different Brazilian states in order to investigate possible intraspecific chromosomal variation between them. Three adult T. pseudomaculata males from each population (Pernambuco, Ceará, Paraíba, Bahia, Rio Grande do Norte, and Piauí) were analyzed by lacto-acetic orcein and C-banding. All of the specimens analyzed exhibited the same cytogenetic characteristics, i.e., 22 chromosomes (20 autosomes and XY), a chromocenter formed by the X and Y sex chromosomes and one pair of autosomes, and heterochromatin blocks in three or four pairs of autosomes. These data confirm that all of the populations analyzed were T. pseudomaculata, and although they may be subject to different selection pressures they have maintained the genetic integrity that characterizes the species.

Differentiation between Triatoma arthurneivai and Triatoma wygodzinskyi (Hemiptera: Reduviidae: Triatominae) using cytotaxonomy.

Using classic morphometric techniques to examine the head and thorax of Triatoma specimens, researchers identified a possible taxonomic problem involving T. arthurneivai (Lent & Martins) and T. wygodzinskyi (Lent). A recent geometric morphometric study indicated that the insects captured outside the Serra do Cipó region, State of Minas Gerais, Brazil, were T. wygodzinskyi. The misidentification of T. arthurneivai as T. wygodzinskyi could result in several problems associated with entoepidemiological lifting, the biological characterization of the species, and phylogenetic reconstruction. For the first time, we describe the use of cytogenetic analysis as a tool for differentiation between T. arthurneivai and T. wygodzinskyi. The results indicated that both species had the same number of chromosomes 2n = 22 (20A + XY). However, analyses of spermatocytes during early prophase indicated that it was possible to differentiate T. arthurneivai and T. wygodzinskyi, because only T. arthurneivai exhibited heteropycnotic blocks distributed in the chromatin. Therefore, we highlight the analysis of spermatocytes as a taxonomic tool for the characterization of T. arthurneivai and T. wygodzinskyi, and suggest that the technique can be used for entoepidemiological lifting in vector control programs. Thus, the results presented here, in conjunction with morphometric analyses, are of utmost taxonomic and epidemiological importance for the identification of T. arthurneivai and T. wygodzinskyi specimens.

New record and cytogenetic analysis of Psammolestes tertius Lent & Jurberg, 1965 (Hemiptera, Reduviidae, Triatominae) from Bahia State, Brazil.

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.

Insights into a hotspot in the Brasiliensis subcomplex (Hemiptera, Triatominae) by analysis of D2 domain of the nuclear gene 28S.

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 (G↔C and T↔G). 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 (G↔T) 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.

Nucleolar-persistence phenomenon during spermatogenesis in genus Meccus (Hemiptera, Triatominae).

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.

Spermatogenesis and nucleolar behavior in Triatoma vandae and Triatoma williami (Hemiptera, Triatominae).

This study describes spermatogenesis in Triatoma vandae and the nucleolar behavior of T. vandae and Triatoma williami, with a cytotaxonomic focus. Analysis of mitotic and meiotic metaphases of T.vandae confirms the species karyotype. T. vandae presents some characteristics during meiosis that differentiate it from T. williami, including the presence of a chromocenter with two sex chromosomes individualized during early prophase, and the presence of a bi- or tripartite corpuscle inpolyploid nuclei. It was possible to observe the compaction of chromatin during prophase resulting in holocentric chromosomes. During metaphase,the autosomes presented a ring shape and the sex chromosomes were in the center of the ring. These chromosomes were separated in anaphase. Although it is common, we did not observe the phenomenon of late migration of the sex chromosomes. By means of silver ion impregnation it was possible to describe nucleologenesis in T. vandae and T. williami. In both species we observed persistence of the nucleolar material duringmeiosis. In addition to the cells in meiotic division, we also observed the presence of polyploid nuclei in the seminiferous tubule walls that nourish the cells during cell division. The nucleolar markings reflect their capacity for synthetic activity. T. vandae and T. williami presented only one nucleolar corpuscle, which reflects low synthetic activity. This study confirms the karyotype of T. vandae, describes characteristics that differentiate T. vandae and T. williami during meiosis, and describes the phenomenon of nucleolar persistence in both species.

Chromosomal evolution in the pallescens group (Hemiptera, Triatominae).

Rhodnius colombiensis, in conjunction with R. pallescens and R. ecuadoriensis, forms the monophyletic pallescens group. Cytogenetic analyses of these closely related species would further our understanding of the taxonomy and evolution of this group. In this study, R. colombiensis was cytogenetically analyzed, and the results were compared with cytogenetic data from other species of the pallescens group, particularly their chromosomal evolution. We found that this triatomine has heteropycnotic blocks in five autosomal bivalents at both metaphase I and II. The derivation of R. colombiensis from R. pallescens led to significant loss of heteropycnotic and heterochromatic regions (approximately 50%). R. ecuadoriensis is the most differentiated of the group because it has lost all heterochromatin and heteropyknotic blocks in the autosomes. Based on the heteropyknotic and heterochromatic pattern of R. colombiensis and the chromosomal evolution analysis of the pallescens group, we suggest that the karyotype of R. colombiensis and R. ecuadoriensis lost its heteropycnotic and heterochromatic blocks during speciation. Furthermore, this loss could be related to adaptation to different environments.

Entoepidemiology of Chagas disease in the Western region of the State of São Paulo from 2004 to 2008, and cytogenetic analysis in Rhodnius neglectus (Hemiptera, Triatominae).

To complement the epidemiological data and assist in the prophylaxis of Chagas disease in the State of São Paulo, we examined entomological lifting conducted in 40 municipalities of the Western region of the state from 2004 to 2008, highlighted the main vector species in this region, and reanalyzed the cytogenetic characteristics of Rhodnius neglectus from 3 different Brazilian states (Formoso/GO, Frutal/MG, Guaíra/SP, and Pitangueiras/SP). The municipalities of Castilho and Santo Antônio do Acaranguá registered the highest relative amounts of notifications. The main species notified in Western São Paulo were Triatoma sordida and R. neglectus. We collected a large number of T. sordida in 2005 and noted the absence of notification of infected insects in 2008. We observed no variation in chromosomal characteristics of R. neglectus of different states. These data are complementary to the survey presented from 1990 to 1999, as the vector species were the same (T. sordida and R. neglectus), with emphasis on T. sordida. We corroborate the future colonization domiciliary initially proposed for T. sordida in the region and underscore the importance of vector control programs in the prophylaxis of Chagas disease. Furthermore, we observed that the populations of R. neglectus in Brazil showed no intraspecific variation and we corroborated the chromosomal patterns originally described. These data are important for understanding the evolution of these hematophagous insects, which are vectors of Chagas disease.

Karyotype of Rhodnius montenegrensis (Hemiptera, Triatominae).

The Triatominae subfamily comprises 6 tribes. The tribe Rhodniini comprises 2 genera and 22 nominal species. Rhodnius montenegrensis (Hemiptera, Triatominae) was recently described as evolutionarily related to R. robustus. Therefore, in order to contribute to karyosystematic study of the tribe Rhodniini, this report describes the number of chromosomes and compares the karyotype of R. montenegrensis to that of all other species in the tribe, in order to determine the karyotypic evolution of the tribe Rhodniini. The seminiferous tubules of adult males, after being removed and fixated on a cover slip, were processed with lacto-aceto-orcein for cytogenetic analysis. R. montenegrensis, as well as all other species of the tribe Rhodniini showed 22 chromosomes (20 autosomes + XY). Thus, we hereby describe the karyotype of the species R. montenegrensis and mainly highlight that the tribe Rhodniini displays karyotypic homogeneity, demonstrating itself as a derived group to a lesser extent when compared to the number of chromosomes of the common ancestors of the subfamily Triatominae.

First cytogenetic study of Cavernicola pilosa Barber, 1937 (Hemiptera, Triatominae).

Cavernicola pilosa is a triatomine species that lives in caves and feeds on bat blood. This vector has a wide geographical distribution, and is found in Brazil, Colombia, Panama, Peru, and Venezuela. Little is known about the reproductive biology of this species, because most previous studies have only characterized its morphology, morphometry, ecology, and epidemiology. Therefore, this study aimed to obtain preliminary data related to spermatogenesis in C. pilosa by conducting cytogenetic analysis. Analysis of the heterochromatic pattern of C. pilosa during the initial prophases revealed that heterochromatic blocks are only present in the sex chromosomes. Based on the analyses of the meiotic metaphase and prophases, we found that the sex determination system of C. pilosa is XY and the chromosomes are holocentric. C. pilosa spermatids are filamentous and have long flagella. It was not possible to detect corpuscle or filament heteropycnosis in spermatids of this species. The initial cytogenetic data presented in this study are important in characterizing the spermatogenesis and heterochromatic patterns of C. pilosa. Our results suggest that adaptation to troglodytism did not result in differences in spermatogenesis in this vector.

Diploid chromosome set of kissing bug Triatoma baratai (Hemiptera, Triatominae).

Triatomines are insects that are taxonomically included in the Hemiptera order and Triatominae subfamily. Based on phenotypic similarity, capacity hybridization, and genetic and ecological aspects, the triatomine species can be grouped into specific complexes and subcomplexes. However, these groupings have not been confirmed. Cytogenetic analyses are important cytotaxonomic tools for improving the taxonomic knowledge of triatomines. Thus, we examined the karyotype of Triatoma baratai and compared the results with those of other species in the Matogrossensis subcomplex in order increase the understanding of vector potential. We also examined the cytotaxonomic classification of this insect. Triatoma baratai, similarly to other species that currently compose the Matogrossensis subcomplex, contains 22 chromosomes (20A + XY). Here, we describe the diploid chromosome set of T. baratai. We confirmed their current classification in the Matogrossensis subcomplex and demonstrated that the species in this subcomplex present karyotype homogeneity.