Cytogenetics and Genome Evolution in the Subfamily Triatominae (Hemiptera, Reduviidae)

Abstract

The subfamily Triatominae (Hemiptera, Reduviidae), vectors of Chagas disease, includes over 140 species. Karyotypic information is currently available for 80 of these species. This paper summarizes the chromosomal variability of the subfamily and how it may reveal aspects of genome evolution in this group. The Triatominae present a highly conserved chromosome number. All species, except 3, present 20 autosomes. The differences in chromosome number are mainly caused by variation in the number of sex chromosomes, due to the existence of 3 sex systems in males (XY, X₁X₂Y and X₁X₂X₃Y). However, inter- and intraspecific differences in the position, quantity and meiotic behavior of constitutive heterochromatin, in the total genome size, and in the location of ribosomal 45S rRNA clusters, have revealed considerable cytogenetic variability within the subfamily. This cytogenetic diversity offers the opportunity to perform cytotaxonomic and phylogenetic studies, as well as structural, evolutionary, and functional analyses of the genome. The imminent availability of the complete genome of Rhodnius prolixus also opens new perspectives for understanding the evolution and genome expression of triatomines. The application of fluorescence in situ hybridization for the mapping of genes and sequences, as well as comparative analyses of genome homology by comparative genomic hybridization will be useful tools for understanding the genomic changes in relation to evolutionary processes such as speciation and adaptation to different environments.

Karyosystematic and karyotype evolution of Panstrongylus lutzi (Neiva & Pinto, 1923) (Hemiptera, Triatominae)

“…Cytogenetic analyses in Panstrongylus were initiated in 1950 with the karyotype description of P. megistus (Schreiber and Pellegrino, 1950). Until now the number of chromosomes in seven species of Panstrongylus was described, of which with the exception of P. megistus which has 21 chromosomes (2n = 18A + X 1 X 2 Y), all other species analyzed (P. chinai, P. geniculatus, P. howardi, P. lignarius, P. rufotuberculatus and P. tupynambai) have 23 chromosomes (2n = 20A + X 1 X 2 Y) (Schreiber and Pellegrino, 1950;Pérez et al, 2002;Panzera et al, 2010).…”

“…Based on homogeneity of the number of chromosomes (2n = 23) and sex determination system (X 1 X 2 Y) of the genus Panstrongylus, Perez et al (2002) suggested that these triatomines were possibly originated from ancestors of North America, because all species of South America [except Triatoma melanocephala (2n = 24), T. vitticeps (2n = 24) and T. tibiamaculata (2n = 23) (Alevi et al, 2012)] have 2n = 22 chromosomes and XY sex determination system (Panzera et al, 2010). These results were recently confirmed based on molecular analysis (Justi et al, 2014).…”

“…Cytogenetic analyses in Panstrongylus were initiated in 1950 with the karyotype description of P. megistus (Schreiber and Pellegrino, 1950). Until now the number of chromosomes in seven species of Panstrongylus was described, of which with the exception of P. megistus which has 21 chromosomes (2n = 18A + X 1 X 2 Y), all other species analyzed (P. chinai, P. geniculatus, P. howardi, P. lignarius, P. rufotuberculatus and P. tupynambai) have 23 chromosomes (2n = 20A + X 1 X 2 Y) (Schreiber and Pellegrino, 1950;Pérez et al, 2002;Panzera et al, 2010).Based on homogeneity of the number of chromosomes (2n = 23) and sex determination system (X 1 X 2 Y) of the genus Panstrongylus, Perez et al (2002) suggested that these triatomines were possibly originated from ancestors of North America, because all species of South America [except Triatoma melanocephala (2n = 24), T. vitticeps (2n = 24) and T. tibiamaculata (2n = 23) (Alevi et al, 2012)] have 2n = 22 chromosomes and XY sex determination system (Panzera et al, 2010). These results were recently confirmed based on molecular analysis (Justi et al, 2014).…”

Distribution of constitutive heterochromatin in Triatoma melanocephala (Hemiptera, Triatominae)

“…However, experimental crosses , molecular (Mendonça et al, 2009;Gardim et al, 2014), enzymatic (Costa et al, 1997), and cytogenetic (Panzera et al, 2010(Panzera et al, , 2012Alevi et al, 2012aAlevi et al, , 2013aSucci et al, 2014) techniques have been used as important tools to aid in the classification of species.…”

“…Cytogenetic data, such as the number of chromosomes and the pattern of constitutive heterochromatin, were also used to group the species of the Brasiliensis subcomplex (Panzera et al, 2010;Alevi et al, 2012aAlevi et al, ,b, 2013aAlevi et al, ,b,c,d,e, 2014a. Thus, cytotaxonomy has turned out to be an important tool in the systematics of triatomines.…”