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

K. C. C. Alevi C. H. L. Imperador E. O. L. Fonseca C. G. S. Santos M. T. V. Azeredo-Oliveira J. A. Rosa J. Oliveira About the authors

1. Scientific Note

Currently, there are 153 species of triatomines, distributed in 18 genera, being all species considered as potential vector of Chagas disease (Alevi et al., 2016ALEVI, K.C.C., MOREIRA, F.F.F., JURBERG, J. and AZEREDO-OLIVEIRA, M.T.V., 2016. Description of diploid chromosome set of (Hemiptera, Triatominae). Triatoma pintodiasiGenetics and Molecular Research, vol. 15, no. 2, pp. 1-9.; Rosa et al., 2017ROSA, J.A., JUSTINO, H.H.G., NASCIMENTO, J.D., MENDONÇA, V.J., ROCHA, C.S., CARVALHO, D.B., FALCONE, R., AZEREDO-OLIVEIRA, M.T.V., ALEVI, K.C.C. and OLIVEIRA, J., 2017. A new species of Rhodnius from Brazil (Hemiptera, Reduviidae, Triatominae). ZooKeys. In press.). The genus Panstrongylus Berg, 1879 is composed of 15 species, being 14 species alive and one fossil. Cytogenetic analyses in Panstrongylus were initiated in 1950 with the karyotype description of P. megistus (Schreiber and Pellegrino, 1950SCHREIBER, G. and PELLEGRINO, J., 1950. Eteropicnosi di autosomi come possible meccanismo di speciazione (Ricerche citologiche su alcuni Emitteri neotropici). Sciencia Genetica, vol. 3, pp. 215-226.). 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 + X1X2Y), all other species analyzed (P. chinai, P. geniculatus, P. howardi, P. lignarius, P. rufotuberculatus and P. tupynambai) have 23 chromosomes (2n = 20A + X1X2Y) (Schreiber and Pellegrino, 1950SCHREIBER, G. and PELLEGRINO, J., 1950. Eteropicnosi di autosomi come possible meccanismo di speciazione (Ricerche citologiche su alcuni Emitteri neotropici). Sciencia Genetica, vol. 3, pp. 215-226.; Pérez et al., 2002PÉREZ, R., HERNÁNDEZ, M., CARACCIO, M., ROSE, V., VALENTE, A., VALENTE, V., MORENO, J., ANGULO, V., SANDOVAL, M., ROLDÁN, J., VARGAS, F., WOLFF, M. and PANZERA, F., 2002. Chromosomal evolution trends of the genus Panstrongylus (Hemiptera, Reduviidae), vectors of Chagas Disease. Infection, Genetics and Evolution, vol. 2, no. 01, pp. 47-56. PMid:12798000. http://dx.doi.org/10.1016/S1567-1348(02)00063-1.
http://dx.doi.org/10.1016/S1567-1348(02)...
; Panzera et al., 2010PANZERA, F., PÉREZ, R., PANZERA, Y., FERRANDIS, I., FERREIRO, M.J. and CALLEROS, L., 2010. Cytogenetics and genome evolution in the subfamily Triatominae (Hemiptera, Reduviidae). Cytogenetics and Genome Research, vol. 128, no. 1-3, pp. 77-87.).

Based on homogeneity of the number of chromosomes (2n = 23) and sex determination system (X1X2Y) of the genus Panstrongylus, Perez et al. (2002)PÉREZ, R., HERNÁNDEZ, M., CARACCIO, M., ROSE, V., VALENTE, A., VALENTE, V., MORENO, J., ANGULO, V., SANDOVAL, M., ROLDÁN, J., VARGAS, F., WOLFF, M. and PANZERA, F., 2002. Chromosomal evolution trends of the genus Panstrongylus (Hemiptera, Reduviidae), vectors of Chagas Disease. Infection, Genetics and Evolution, vol. 2, no. 01, pp. 47-56. PMid:12798000. http://dx.doi.org/10.1016/S1567-1348(02)00063-1.
http://dx.doi.org/10.1016/S1567-1348(02)...
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., 2012ALEVI, K.C.C., MENDONÇA, P.P., PEREIRA, N.P., ROSA, J.A. and AZEREDO-OLIVEIRA, M.T.V., 2012. Karyotype of Triatoma melanocephala Neiva and Pinto (1923). Does this species fit in the Brasiliensis subcomplex?Infection, Genetics and Evolution, vol. 12, no. 08, pp. 1652-1653. PMid:22760157. http://dx.doi.org/10.1016/j.meegid.2012.06.011.
http://dx.doi.org/10.1016/j.meegid.2012....
)] have 2n = 22 chromosomes and XY sex determination system (Panzera et al., 2010PANZERA, F., PÉREZ, R., PANZERA, Y., FERRANDIS, I., FERREIRO, M.J. and CALLEROS, L., 2010. Cytogenetics and genome evolution in the subfamily Triatominae (Hemiptera, Reduviidae). Cytogenetics and Genome Research, vol. 128, no. 1-3, pp. 77-87.). These results were recently confirmed based on molecular analysis (Justi et al., 2014JUSTI, S.A., RUSSO, C.A.M., MALLET, J.R.S., OBARA, M.T. and GALVÃO, C., 2014. Molecular phylogeny of Triatomini (Hemiptera: Reduviidae: Triatominae). Parasites & Vectors, vol. 7, no. 149, pp. 1-12.).

Thus, in order to assist in the chromosomal and evolutionary knowledge of the genus Panstrongylus and Triatominae subfamily, this study aimed to analyze the karyotype of P. lutzi and compare with karyotypes already described for other species of the triatomines.

One adult male of P. lutzi was collected in wild environment in the State of Bahia, Brazil (S 12.41’407 “, W 039.26’210” and elevation 167 meters). We justify that only one specimen was analyzed by the absence of P. lutzi in Brazilian insectaries and mainly by the difficulty of collecting and maintaining of these species in the laboratory, since for cytogenetic analyzes the insects might not be killed or fixed in alcohol (as occurs for molecular analysis). The seminiferous tubules of adult males were torn and fixed to a cover slip. They then underwent the cytogenetic technique of Lacto-acetic orcein (De Vaio et al., 1985DE VAIO, E.S., GRUCCI, B., CASTAGNINO, A.M., FRANCA, M.E. and MARTINEZ, M.E., 1985. Meiotic differences between three triatomine species (Hemiptera:Reduviidae). Genetica, vol. 67, no. 3, pp. 185-191. http://dx.doi.org/10.1007/BF02424489.
http://dx.doi.org/10.1007/BF02424489...
with modifications according to Alevi et al., 2012ALEVI, K.C.C., MENDONÇA, P.P., PEREIRA, N.P., ROSA, J.A. and AZEREDO-OLIVEIRA, M.T.V., 2012. Karyotype of Triatoma melanocephala Neiva and Pinto (1923). Does this species fit in the Brasiliensis subcomplex?Infection, Genetics and Evolution, vol. 12, no. 08, pp. 1652-1653. PMid:22760157. http://dx.doi.org/10.1016/j.meegid.2012.06.011.
http://dx.doi.org/10.1016/j.meegid.2012....
) and analyzed using a Jenaval light microscope (Zeiss). For the characterization of the karyotype were analyzed 50 mitotic metaphases (I and II).

As well as was observed recently by Santos et al. (2016)SANTOS, S.M., POMPOLO, S.G., GONÇALVES, T.C.M., FREITAS, S.P.C., RANGEL, E.F. and SANTOS-MALLET, J.R.S., 2016. New sex-determination system in the genus (Hemiptera: Reduviidae) revealed by chromosomal analysis of PanstrongylusPanstrongylus lutzi.Parasites & Vectors, vol. 9, no. 1, pp. 295. PMid:27209318. http://dx.doi.org/10.1186/s13071-016-1574-6.
http://dx.doi.org/10.1186/s13071-016-157...
, P. lutzi presented a different karyotype of all species of the genus Panstrongylus, namely, 2n = 24 (20A + X1X2X3Y), being the Y sex chromosome heteropycnotic (Figure 1). This number of chromosomes is very peculiar because it was described to only three other species in subfamily Triatominae: T. melanocephala (Alevi et al., 2012ALEVI, K.C.C., MENDONÇA, P.P., PEREIRA, N.P., ROSA, J.A. and AZEREDO-OLIVEIRA, M.T.V., 2012. Karyotype of Triatoma melanocephala Neiva and Pinto (1923). Does this species fit in the Brasiliensis subcomplex?Infection, Genetics and Evolution, vol. 12, no. 08, pp. 1652-1653. PMid:22760157. http://dx.doi.org/10.1016/j.meegid.2012.06.011.
http://dx.doi.org/10.1016/j.meegid.2012....
), T. vitticeps (Schreiber and Pellegrino, 1950SCHREIBER, G. and PELLEGRINO, J., 1950. Eteropicnosi di autosomi come possible meccanismo di speciazione (Ricerche citologiche su alcuni Emitteri neotropici). Sciencia Genetica, vol. 3, pp. 215-226.) and T. eratyrusiformis (Ueshima, 1966UESHIMA, N., 1966. Cytotaxonomy of the Triatominae (Reduviidae, Hemiptera). Chromosoma, vol. 18, no. 01, pp. 97-122. http://dx.doi.org/10.1007/BF00326447.
http://dx.doi.org/10.1007/BF00326447...
).

Figure 1
Karyotype of the Panstrongylus lutzi. Note 2n = 24 (20A + X1X2X3Y) chromosomes. X: X sex chromosome; Y: Y sex chromosome. Bar: 10 µm.

Starting from the principle that the ancestral karyotype of Panstrongylus is 2n = 23 (Perez et al., 2002PÉREZ, R., HERNÁNDEZ, M., CARACCIO, M., ROSE, V., VALENTE, A., VALENTE, V., MORENO, J., ANGULO, V., SANDOVAL, M., ROLDÁN, J., VARGAS, F., WOLFF, M. and PANZERA, F., 2002. Chromosomal evolution trends of the genus Panstrongylus (Hemiptera, Reduviidae), vectors of Chagas Disease. Infection, Genetics and Evolution, vol. 2, no. 01, pp. 47-56. PMid:12798000. http://dx.doi.org/10.1016/S1567-1348(02)00063-1.
http://dx.doi.org/10.1016/S1567-1348(02)...
), during karyotype evolution of P. megistus and P. lutzi occurred simploidy (fusion) of a pair of autosomes (Perez et al., 2002PÉREZ, R., HERNÁNDEZ, M., CARACCIO, M., ROSE, V., VALENTE, A., VALENTE, V., MORENO, J., ANGULO, V., SANDOVAL, M., ROLDÁN, J., VARGAS, F., WOLFF, M. and PANZERA, F., 2002. Chromosomal evolution trends of the genus Panstrongylus (Hemiptera, Reduviidae), vectors of Chagas Disease. Infection, Genetics and Evolution, vol. 2, no. 01, pp. 47-56. PMid:12798000. http://dx.doi.org/10.1016/S1567-1348(02)00063-1.
http://dx.doi.org/10.1016/S1567-1348(02)...
) and agmatoploidy (fission) of X sex chromosome, respectively (Figure 2). The number of chromosomes of the P. megistus (2n = 21) and P. lutzi (2n = 24) can be used as a taxonomic tool to differentiate this species from all species of genus Panstrongylus (2n = 23), as well as allows distinguishing them from other 85 species of Triatominae subfamily that presents 22 (55 species) or 23 (30 species) chromosomes (Alevi et al., 2016ALEVI, K.C.C., MOREIRA, F.F.F., JURBERG, J. and AZEREDO-OLIVEIRA, M.T.V., 2016. Description of diploid chromosome set of (Hemiptera, Triatominae). Triatoma pintodiasiGenetics and Molecular Research, vol. 15, no. 2, pp. 1-9.; Bardella et al., 2016BARDELLA, V.B., PITA, S., VANZELA, A.L.L., GALVÃO, C. and PANZERA, F., 2016. Heterochromatin base pair composition and diversification in holocentric chromosomes of kissing bugs (Hemiptera, Reduviidae). Memórias do Instituto Oswaldo Cruz, vol. 111, no. 10, pp. 614-624. PMid:27759763. http://dx.doi.org/10.1590/0074-02760160044.
http://dx.doi.org/10.1590/0074-027601600...
; Mendonça et al., 2016MENDONÇA, V.J., ALEVI, K.C.C., PINOTTI, H., GURGEL-GONGALVES, R., PITA, S., GUERRA, A.L., PANZERA, F., ARAÚJO, R.F., AZEREDO-OLIVEIRA, M.T.V. and ROSA, J.A., 2016. Revalidation of Sherlock & Serafim, 1967 (Hemiptera: Reduviidae) and phylogeny of the species. Triatoma bahiensisT. brasiliensisZootaxa, vol. 4107, no. 2, pp. 239-254. PMid:27394816. http://dx.doi.org/10.11646/zootaxa.4107.2.6.
http://dx.doi.org/10.11646/zootaxa.4107....
; Rosa et al., 2017ROSA, J.A., JUSTINO, H.H.G., NASCIMENTO, J.D., MENDONÇA, V.J., ROCHA, C.S., CARVALHO, D.B., FALCONE, R., AZEREDO-OLIVEIRA, M.T.V., ALEVI, K.C.C. and OLIVEIRA, J., 2017. A new species of Rhodnius from Brazil (Hemiptera, Reduviidae, Triatominae). ZooKeys. In press.).

Figure 2
Karyotype evolution in the genus Panstrongylus. Note that from ancestral karyotype 2n = 23, occurred three evolutionary events during the speciation of these vectors: (1) agmatoploidy in X sex chromosome, resulting in karyotype 2n = 24 (P. lutzi); (2) absence of events that alter the karyotype numerically, keeping the same ancestor number 2n = 23 (P. chinai, P. geniculatus, P. howardi, P. lignarius, P. rufotuberculatus and P. tupynambai); (3) simploidy in a pair of autosomes, resulting in karyotype 2n = 21 (P. megistus). AK: ancestral karyotype; ASC: agmatoploidy in sex chromosome; SA: simploidy in autosomes.

Jurberg et al. (2001)JURBERG, J., CARCAVALLO, R.U. and LENT, H., 2001. sp.n. do estado da bahia, Brasil (hemiptera, reduviidae, triatominae). Panstrongylus sherlockiEntomología y Vectores, vol. 8, no. 2, pp. 261-274. based on chromatic and morphological analysis of only one specimen collected in Bahia described P. sherlocki as sister species of P. lutzi. However, Garcia et al. (2005)GARCIA, M.H.H.M., SOUZA, L., SOUZA, R.C.M., PAULA, A.S., BORGES, E.C., BARBOSA, S.E., SCHOFFIELD, C.J. and DIOTAIUTI, L., 2005. Occurrence and variability of Panstrongylus lutzi in the state of Ceará, Brazil. Revista da Sociedade Brasileira de Medicina Tropical, vol. 38, no. 5, pp. 410-415. PMid:16172758. http://dx.doi.org/10.1590/S0037-86822005000500010.
http://dx.doi.org/10.1590/S0037-86822005...
when analyze P. lutzi coming from the municipalities of Sobral (Bahia) and Crateús (Ceará) observed high variability in morphological and morphometric characteristics and they classified the morphotypes that had the characteristics of P. sherlocki as P. lutzi. On that basis, P. sherlocki became considered as synonymous with P. lutzi (Schofield and Galvão, 2009SCHOFIELD, C.J. and GALVÃO, C., 2009. Classification, evolution, and species groups within the Triatominae. Acta Tropica, vol. 110, no. 2-3, pp. 88-100.). However, due to peculiarity observed in the karyotype of P. lutzi, we suggest that new karyotypic studies should be conducted on specimens initially classified as P. sherlocki by Jurberg et al. (2001)JURBERG, J., CARCAVALLO, R.U. and LENT, H., 2001. sp.n. do estado da bahia, Brasil (hemiptera, reduviidae, triatominae). Panstrongylus sherlockiEntomología y Vectores, vol. 8, no. 2, pp. 261-274., because if a different karyotype of 2n = 24 is observed, the number of chromosomes would support the revalidation of the species.

Thus, this paper describes the number of chromosomes of P. lutzi [2n = 24 (20A + X1X2X3Y)], suggests that karyotype arose from one agmatoploidy event of the X sex chromosome and mainly apply these data as taxonomic tool to differentiate this vector of other species of the genus Panstrongylus, as well as subfamily Triatominae.

Acknowledgements

The study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (process numbers 2013/19764-0, Brazil) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil).

  • (With 2 figures)

References

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  • BARDELLA, V.B., PITA, S., VANZELA, A.L.L., GALVÃO, C. and PANZERA, F., 2016. Heterochromatin base pair composition and diversification in holocentric chromosomes of kissing bugs (Hemiptera, Reduviidae). Memórias do Instituto Oswaldo Cruz, vol. 111, no. 10, pp. 614-624. PMid:27759763. http://dx.doi.org/10.1590/0074-02760160044
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    » http://dx.doi.org/10.1007/BF02424489
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    » http://dx.doi.org/10.1186/s13071-016-1574-6
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    » http://dx.doi.org/10.1007/BF00326447

Publication Dates

  • Publication in this collection
    25 May 2017
  • Date of issue
    Feb 2018

History

  • Received
    11 July 2016
  • Accepted
    17 Sept 2016
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