Cytotaxonomy of the Maculata subcomplex (Hemiptera, Triatominae)

1 Scientific Note

Triatomines are hematophagous insects belonging to the Hemiptera order and Triatominae subfamily. All members of this subfamily are potential vectors of Chagas disease (Tartarotti et al., 2006). The Maculata subcomplex is composed of four species: Triatoma maculata, T. pseudomaculata, T. arthurneivai and T. wygodzinskyi. Recent phylogenetic analyzes showed conflicting results in relation to monophyly of this complex, because Justi et al. (2014) have failed to rescue the monophyly of the subcomplex and observed that T. maculata was more related to the species of the Brasiliensis subcomplex than the species of Maculata subcomplex (T. arthurneivai was not used in the study).

By means of cytogenetic characterization of the spermatocytes (prophase I), Santos et al. (2007) proposed that T. maculata, T. pseudomaculata and T. arthurneivai presented different heterochromatin patterns distribution and meiotic behavior. Panzera et al. (2010) describe the pattern heterochromatic of T. wygodzinskyi as identical to that observed for T. arthurneivai. However, Carbajal-de-La-Fuente et al. (2010) highlight that in many works of literature T. wygodzinskyi was erroneously classified as T. arthurneivai. Thus, this work describes the heterochromatic pattern of all species of the Maculata subcomplex, with cytotaxonomic focus.

At least two males from each species were used. They had been assigned by the FCFAR/UNESP, Araraquara, São Paulo, Brazil, FIOCRUZ, Rio de Janeiro, Brazil and CPqRR-FIOCRUZ, Minas Gerais, Brazil. The seminiferous tubules of adult males were torn and fixed to a cover slip. They then underwent the cytogenetic technique of C-banding (Sumner, 1972) and analyzed using a Jenaval light microscope (Zeiss).

By analyzing of the distribution of the pattern of constitutive heterochromatin in spermatocytes in prophase I has been possible to differentiate all species of Maculata subcomplex: T. maculata (Figure 1A) showed a heterochromatic chromocenter formed by the sex chromosomes (arrow) and small heterochromatic blocks dispersed in nucleus; T. pseudomaculata (Figure 1B) showed a heterochromatic chromocenter formed by the sex chromosomes plus one pair of autosomes (arrow) and some heterochromatic blocks dispersed in the nucleus; T. wygodzinskyi (Figure 1C) showed only one heterochromatic chromocenter formed by the sex chromosomes (arrow) and T. arthurneivai (Figure 1D) showed a heterochromatic chromocenter formed by the sex chromosomes (arrow) and large heterochromatic blocks dispersed in the nucleus.

Figure 1
Constitutive heterochromatin in spermatocytes (prophase I) of all species of Maculata subcomplex. (A) Note the heterochromatic chromocenter formed by the sex chromosomes (arrow) and small heterochromatic blocks dispersed in T. maculata; (B) Note the heterochromatic chromocenter formed by the sex chromosomes plus one pair of autosomes (arrow) and some heterochromatic blocks dispersed in T. pseudomaculata; (C) Note witch only one heterochromatic chromocenter formed by the sex chromosomes (arrow) in T. wygodzinskyi; (D) Note the heterochromatic chromocenter formed by the sex chromosomes (arrow) and large heterochromatic blocks dispersed in T. arthurneivai. Bar: 10 μm.

Schofield (1988) suggests that T. maculata and T. pseudomaculata species are derived from a common ancestor that was dispersed passively through the feathers of migratory birds and isolated geographically. These species are very similar from the morphological point of view (Corrêa and Espinola, 1964) and cytogenetic analysis described above confirm the data initially described by Santos et al. (2007) and corroborate the specific status of these triatomines. We suggest that during the speciation of T. pseudomaculata, heterochromatin loss events were involved in genomic reorganization with loss of heterochromatin, as has been observed for the pallescens group (Alevi et al., 2015).

The phylogenetic relationship between T. maculata and Brasiliensis subcomplex reported by Justi et al. (2014) can be confirmed by standard heterochromatin of the species. However, the meiotic behavior of these vectors is different, since during prophase T. maculata, the chromocenter is formed by sex chromosomes, different of the species the Brasiliensis subcomplex which has the chromocenter form by sex chromosomes plus one pair of autosomes.

T. wygodzinskyi was described based on specimens collected in Santa Rita de Caldas, in southern Minas Gerais, Brazil and initially classified as T. arthurneivai (Lent, 1951). Different from the cytogenetic characteristics described initially, our results show that these species display large differences in heterochromatic pattern being the genetic material of T. arthurneivai rich in constitutive heterochromatin. Thus, we emphasize that the specimens analyzed by Santos et al. (2007) were T. wygodzinskyi and not T. arthurneivai as classified by the authors.

Thus, in the present study demonstrated that the analysis of heterochromatic pattern is a cytotaxonomic tool of utmost importance to characterize the species of Maculata subcomplex.

Acknowledgments

We are grateful to the agencies FAPESP (processes nº 2013/19764-0) and CNPq.

• (With 1 figure)

References

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Publication Dates

• Publication in this collection
  13 Mar 2017
• Date of issue
  Nov 2017

History

• Received
  15 Dec 2015
• Accepted
  02 June 2016