Climate and Environmental Changes and Their Potential Effects on the Dynamics of Chagas Disease: Hybridization in Rhodniini (Hemiptera, Triatominae).

Chagas disease affects about eight million people. In view of the issues related to the influence of anthropogenic changes in the dynamics of the distribution and reproductive interaction of triatomines, we performed experimental crosses between species of the Rhodniini tribe in order to evaluate interspecific reproductive interactions and hybrid production capacity. Reciprocal crossing experiments were conducted among Rhodnius brethesi × R. pictipes, R. colombiensis × R. ecuadoriensis, R. neivai × R. prolixus, R. robustus × R. prolixus, R. montenegrensis × R. marabaensis; R. montenegrensis × R. robustus, R. prolixus × R. nasutus and R. neglectus × R. milesi. With the exception of crosses between R. pictipes ♀ × R. brethesi ♂, R. ecuadoriensis ♀ × R. colombiensis ♂ and R. prolixus ♀ × R. neivai ♂, all experimental crosses resulted in hybrids. Our results demonstrate that both allopatric and sympatric species produce hybrids, which can generate concern for public health agencies in the face of current anthropogenic events. Thus, we demonstrate that species of the Rhodniini tribe are capable of producing hybrids under laboratory conditions. These results are of great epidemiological importance and raise an important discussion about the influence of climatic and environmental interactions on Chagas disease dynamics.

Karyotype Evolution in Triatominae (Hemiptera, Reduviidae): The Role of Chromosomal Rearrangements in the Diversification of Chagas Disease Vectors.

Several cytogenetic studies have already been performed in Triatominae, such that different karyotypes could be characterized (ranging from 2n = 21 to 25 chromosomes), being the changes in the number of chromosomes related mainly to fusion and fission events. These changes have been associated with reproductive isolation and speciation events in other insect groups. Thus, we evaluated whether different karyotypes could act in the reproductive isolation of triatomines and we analyzed how the events of karyotypic evolution occurred along the diversification of these vectors. For this, experimental crosses were carried out between triatomine species with different karyotypes. Furthermore, based on a phylogeny with 88 triatomine taxa (developed with different molecular markers), a reconstruction of ancestral karyotypes and of anagenetic and cladogenetic events related to karyotypic alterations was performed through the ChromoSSE chromosomal evolution model. All crosses performed did not result in hybrids (prezygotic isolation in both directions). Our modeling results suggest that during Triatominae diversification, at least nine cladogenetic events may be associated with karyotype change. Thus, we emphasize that these alterations in the number of chromosomes can act as a prezygotic barrier in Triatominae (karyotypic isolation), being important evolutionary events during the diversification of the species of Chagas disease vectors.

Revisiting the Hybridization Processes in the Triatoma brasiliensis Complex (Hemiptera, Triatominae): Reproductive Isolation between Triatoma petrocchiae and T. b. brasiliensis and T. lenti.

Triatoma petrocchiae is a species morphologically similar to T. b. brasiliensis (which resulted in a synonymization event); despite this similarity, genetic, morphological, and experimental crossbreeding studies confirmed the specific status of T. petrocchiae. Considering that both species have been reported living in sympatry and that, for a long time, most species of the T. brasiliensis complex were considered only chromatic variants of T. b. brasiliensis, we carried out experimental crosses between T. b. brasiliensis and T. petrocchiae (to confirm whether these species are reproductively isolated) and between T. lenti and T. petrocchiae (to assess whether T. petrocchiae also presents prezygotic isolation with the other species of the T. brasiliensis complex). Reciprocal experimental crosses were conducted, and weekly, the eggs were collected, counted, and separated in new containers to assess the hatch rate. Neither cross resulted in hybrids, demonstrating that there are pre-zygotic reproductive barriers installed between T. petrocchiae and the other species of the T. brasiliensis complex. On the basis of the results above, we demonstrated that T. petrocchiae is reproductively isolated from T. b. brasiliensis and T. lenti. Furthermore, we suggest that T. petrocchiae is the species most derived from the T. brasiliensis complex.

CytoKey: Identification Key for the Chagas Disease Vectors of the Largest Brazilian Urban Center (São Paulo State), Based on Cytogenetic Data.

Chagas disease is caused by the protozoan Trypanosoma cruzi. This disease is distributed in 21 Latin American countries, where it is mostly vector-borne. In Brazil, there are 68 triatomine species. To date, the epidemiological surveys indicate that the state of São Paulo presents 11 species of triatomines, and most of these species have already been collected in a home environment and found to be infected with T. cruzi. Problems in correctly identifying species can lead to incorrect panorama of distribution of Chagas disease vectors. Thus, we developed an identification key for the triatomines of the state of São Paulo, based on cytogenetic data. With the exception of Panstrongylus diasi that does not present cytogenetic data available in the literature, all species were differentiated by cytogenetic characteristics. We emphasize the importance of using this key as a simple and objective tool in the entoepidemiological surveys conducted by the vector control programs.

Genetic Structure of Brazilian Populations of Triatoma sordida (Stål, 1859) (Hemiptera, Triatominae) by Means of Chromosomal Markers.

Triatoma sordida is among the main Brazilian species considered as Chagas disease vectors. The genetic studies are directed mainly to phylogenetic questions because this species possibly have suffered cryptic speciation. Furthermore, there are few studies that analyzed the structure and genetic variability of specimens from Brazil and that showed low genetic diversity and strong genetic structuring of the population samples. Therefore, because of great epidemiological importance of T. sordida and mainly the restriction of genetic characterization of this vector only for populations of Minas Gerais state, this article performs a genetic analysis of the T. sordida from seven different Brazilian states (representing different biomes), by means of cytogenetic markers. All analyzed specimens presents the same cytogenetic characteristics: early meiotic prophase with several heterochromatic bodies dispersed in the nucleus (CG-rich), being one of them formed by the associated sex chromosomes surrounded by some autosomal heterochromatic regions, meiotic metaphase with most autosomal pairs exhibiting a C-heterochromatic block in one chromosomal end (CG-rich), Y sex chromosome fully heterochromatin (AT-rich), and X chromosome may present a small C-block (CG-rich). These results are important because the chromosomal markers enable to confirm and expand the low genetic diversity for all Brazilian states occupied by T. sordida, suggesting that all Brazilian populations were originated from a small ancestral population and possibly dispersed to other biomes by founder effect. In addition, we suggest that T. sordida from Brazil are not suffering cryptic speciation and we confirm the classification of all Brazilian examples as T. sordida sensu stricto.