Hybrid Collapse Confirms the Specific Status of Triatoma bahiensis Sherlock and Serafim, 1967 (Hemiptera, Triatominae), an Endemic Species in Brazil.

Six to seven million people worldwide are estimated to be infected with Trypanosoma cruzi, the etiologic agent of Chagas disease transmitted mainly by triatomines. Triatoma bahiensis was recently collected in the Brazilian state of Bahia and revalidated using different approaches. The main criterion used to define a "good" biological species is reproductive isolation, so we evaluated the cytogenetics of first-generation (F1) hybrids resulting from the experimental cross between T. bahiensis females and Triatoma lenti males to possibly characterize the postzygotic isolation associated with the hybrid breakdown. All cells analyzed presented a karyotype of 2n = 22 and a pair of univalent autosomes. This chromosome behavior represents hybrid collapse and underscores the specific status of T. bahiensis. Thus, we have characterized the presence of the hybrid collapse phenomenon in an experimental cross, and we confirm the specific status of T. bahiensis, thus contributing to the Triatominae taxonomy.

D2 Region of the 28S RNA Gene: A Too-Conserved Fragment for Inferences on Phylogeny of South American Triatomines.

The brasiliensis complex is composed of five triatomine species, and different approaches suggest that Triatoma lenti and Triatoma petrochiae may be the new members. Therefore, this study sought to analyze the phylogenetic relationships within this complex by means of the D2 region of the 28S RNA gene, and to analyze the degree of polymorphism and phylogenetic significance of this gene for South American triatomines. Phylogenetic analysis by using sequence fragments of the D2 domain did not allow to perform phylogenetic inferences on species within the brasiliensis complex, because the gene alignment composed of a matrix with 37 specimens exhibited only two variable sites along the 567 base pairs used. Furthermore, if all South American species are included, only four variable sites were detected, reflecting the high degree of gene conservation. Therefore, we do not recommend the use of this gene for phylogenetic reconstruction for this group of Chagas disease vectors.

Chromatoid body: remnants of nucleolar proteins during spermatogenesis in triatomine (Heteroptera, Triatominae).

In this study, we analyzed fibrillarin nucleolar protein expression in CBs of spermatogenic cells from testicular follicles of Triatoma sordida and Triatoma infestans. In the structural and ultrastructural analysis, it was used impregnation by silver ions, immunocytochemistry, immunofluorescence and transmission electron microscopy using antibodies against fibrillarin. Regarding the results, the fibrillarin nucleolar protein marked the nucleus and some cytoplasmic spots of germ cells during spermatogenesis in triatomines. These data suggest that fibrillarin could be a constituent of the CB that was most likely derived from nucleolar fragmentation. This is the first time that fibrillarin protein expression has been shown in the CB during spermatogenesis progression in triatomines. The knowledge regarding CB constituents may help to expand the understanding of the physiological role of this structure and the role that it plays in the reproductive biology of triatomines, which are vectors of Chagas Disease.