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

1. 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.

Cytogenetic analysis on the species of the Rhodnius genus showed chromosomal homogeneity, since all species are the same karyotype, namely, 2n = 22 (20 autosomes + XY) (Pita et al., 2013; Alevi et al., 2015a; Rosa et al., 2017) and FISH markings with the 45S probe restricted to the sex chromosomes (Pita et al., 2013). However, chromosomal intraspecific variation have been identified in R. ecuadoriensis (Pita et al., 2013) and R. pallescens (Gomez-Palacio et al., 2008).

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 (Galvao et al., 2003). R. nasutus is a species of prolixus complex observed in different Brazilian states and Argentina (Galvao et al., 2003). This species and R. taquarussuensis are the only species of prolixus complex which presents dispersed heterochromatin in the nucleus and autosomes (Perez 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, Sao 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).

Absence of chromosomal intraspecific variation was also observed for R. neglectus (Alevi et al., 2015b), Panstrongylus megistus (Alevi et al., 2015c), Triatoma brasiliensis (Panzera et al., 2000) and T. pseudomaculata (Imperador et al., 2016). On the other hand, chromosomal intraspecific variation was already reported in Triatominae subamily for the following species: T. sordida (Panzera et al., 1997) T. infestans (Panzera et al., 2004), T. dimidiata (Panzera et al., 2006), P. geniculatus (Crossa et al., 2002), R. ecuadoriensis (Pita et al., 2013) and R. pallescens (Gomez-Palacio et al., 2008).

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.

http://dx.doi.org/10.1590/1519-6984.167196

Acknowledgements

The study was supported by Fundajao de Amparo a Pesquisa do Estado de Sao Paulo (process number 2013/19764-0 and 2015/11372-1) and Conselho Nacional de Desenvolvimento Cientlfico e Tecnologico (CNPq, Brazil).

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A. Ravazi (a), K. C. C. Alevi (a) *, J. Oliveira (b), J. A. Rosa (b) and M. T. V. Azeredo-Oliveira (a)

(a) Laboratorio de Biologia Celular, Departamento de Biologia, Instituto de Biociencias, Letras e Ciencias Exatas--IBILCE, Universidade Estadual Paulista "Julio de Mesquita Filho"--UNESP, Rua Cristovao Colombo, 2265, Jardim Nazareth, CEP 15054-000, Sao Jose do Rio Preto, SP, Brazil

(b) Laboratorio de Parasitologia, Departamento de Ciencias Biologicas, Faculdade de Ciencias Farmaceuticas--FCFAR, Universidade Estadual Paulista "Julio de Mesquita Filho"--UNESP, Rodovia Araraquara-Jau, Km 1, CEP 14801-902, Araraquara, SP, Brazil

* e-mail: e-mail: kaiochaboli@hotmail.com

Received: July 28, 2016--Accepted: August 15, 2016--Distributed: February 28, 2018

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

                              Size of Sex   Heterocromatin
R. prolixus     Karyotype     Chromosome     in Autosomes

Venezuela     2n = 20A + XY       X>Y           Absent
Colombia      2n = 20A + XY       X>Y           Absent
Costa Rica    2n = 20A + XY       X>Y           Absent
R. nasutus
Brazil        2n = 20A + XY       X>Y          Present
Argentina     2n = 20A + XY       X>Y          Present

                Heterocromatin
R. prolixus   in Sex Chromosomes

Venezuela       Only in the Y
Colombia        Only in the Y
Costa Rica      Only in the Y
R. nasutus
Brazil          Only in the Y
Argentina       Only in the Y

Article Details

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Title Annotation:	Notes and Comments
Author:	Ravazi, A.; Alevi, K.C.C.; Oliveira, J.; Rosa, J.A.; Azeredo-Oliveira, M.T.V.
Publication:	Brazilian Journal of Biology
Date:	Feb 1, 2018
Words:	1734
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