Cytogenetic analysis in different populations of Rhodnius prolixus and R . nasutus from different countries of South America

aLaboratório de Biologia Celular, Departamento de Biologia, Instituto de Biociências, Letras e Ciências Exatas – IBILCE, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Rua Cristóvão Colombo, 2265, Jardim Nazareth, CEP 15054-000, São José do Rio Preto, SP, Brazil bLaboratório de Parasitologia, Departamento de Ciências Biológicas, Faculdade de Ciências Farmacêuticas – FCFAR, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Rodovia Araraquara-Jaú, Km 1, CEP 14801-902, Araraquara, SP, Brazil


Scientific Note
Currently 153 species of Triatominae subfamily are known, divided in 18 genera and six tribes (Alevi et al., 2016;Rosa et al., 2017).The Rhodniini consisted of 23 species: three of the Psammolestes genus and 20 of the Rhodnius genus.
Rhodnius prolixus is one of the main species of prolixus complex because it has a wide geographic distribution, being found in Brazil, Bolivia, Colombia, Costa Rica, El Salvador, Ecuador, Guatemala, Guyana, French Guyana, Honduras, Mexico, Nicaragua, Panama, Suriname, Trinidad and Venezuela (Galvão et al., 2003).R. nasutus is a species of prolixus complex observed in different Brazilian states and Argentina (Galvão et al., 2003).This species and R. taquarussuensis are the only species of prolixus complex which presents dispersed heterochromatin in the nucleus and autosomes (Pérez et al., 1992;Rosa et al., 2017).
Thus, this study aimed to analyze whether different populations of R. prolixus from Venezuela, Costa Rica and Colombia, and R. nasutus from Brazil and Argentina, present chromosomal intraspecific variation.
Five adult males of the R. prolixus of Venezuela, Colombia and Costa Rica and R. nasutus of Brazil and Argentina were analyzed the cytogenetically.The insects were provided by FCFAR/UNESP, Campus Araraquara, São Paulo, Brazil and FIOCRUZ, Rio de Janeiro, Brazil.The testicles were removed, the slides containing the seminiferous tubules were prepared by crushing and cell stained with classical cytogenetic techniques Orcein Lacto-acetic and C-Banding and examined under a light microscopy.
Chromosomal intraspecific variation was not observed for the specimens of R. prolixus and R. nasutus from different countries, because all specimens showed the same karyotype, the same morphological characteristics for the autosomes and sex chromosomes and the same pattern of constitutive heterochromatin (Table 1).
The chromosomal homogeneity observed between R. prolixus from different locations corroborates the results of Pita et al. (2013) and Monteiro et al. (2003) who described the absence of polymorphism in the position of the 45S gene and low variability for R. prolixus, respectively.Furthermore, Alevi et al. (2015d) did not observe significant differences between the reproductive aspects of these vectors, since the analysis of cystic spermatogenesis of R. prolixus originating in Colombia and Costa Rica, were similar.
R. nasutus although it also does not show intraspecific variation, can be easily distinguished from other members of the complex by heterochromatin in chromatin and chromosomes.The wealth of heterochromatin is quite peculiar in Rhodniini tribe, which could be a source of variability between populations of different countries under different evolutionary pressures, as well as observed for R. pallescens (Gomez-Palacio et al., 2008).Thus, we observed that R. prolixus from Venezuela, Colombia and Costa Rica and R. nasutus from Brazil and Argentina presents chromosomal homogeneity.Our results together with the literature data for R. prolixus (Monteiro et al., 2003;Pita et al., 2013) can direct the development of specific control mechanisms by the low genetic and chromosomal variation presented in this vector.

Table 1 .
Chromosomal characteristics of different populations of the R. prolixus and R. nasutus.