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

Abstract

Scientific NoteCurrently, there are 153 species of triatomines, distributed in 18 genera, being all species considered as potential vector of Chagas disease Rosa et al., 2017). 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, 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).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., 1985 with modifications according to Alevi et al., 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), P. lutzi presented a different karyotype of all species of the genus Panstrongylus, namely, 2n = 24 (20A + X 1 X 2 X 3 Y), 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., 2012), T. vitticeps (Schreiber and Pellegrino, 1950) and T. eratyrusiformis (Ueshima, 1966).Starting from the principle that the ancestral karyotype of Panstrongylus is 2n = 23 (Perez et al., ...

Karyotype Evolution of Chagas Disease Vectors (Hemiptera, Triatominae)

“…8,[17][18][19] Gardim et al 20 pointed out the need for a general revision in the tribe Triatomini because Panstrongylus cannot be clustered separately from Triatoma. For example, the clade geniculatus consists of Panstrongylus spp., flavida complex, and Triatoma tibiamaculata, 5 and all studied species of this clade [except Panstrongylus megistus (Burmeister, 1835) and Panstrongylus lutzi (Neiva & Pinto, 1923)] 21,22 presented 2n = 23 (20A + X 1 X 2 Y), 9,21 which confirms the evolutionary relationship proposed. Based on the ancestral karyotype (2n = 22), we suggest that during the divergence of the common ancestor of the clade geniculatus an agmatoploidy in the X sex chromosome has happened, which resulted in karyotype 2n = 23 (karyotype shared by Panstrongylus spp., Nesotriatoma spp., and T. tibiamaculata).…”

“…However, during the karyotypic evolution of Panstrongylus, two events occurred: simploidy in a pair of autosomes in P. megistus 2n = 21 (18A + X 1 X 2 Y) 21 [a less common event, possibly related to a vicariant divergence between P. megistus and T. tibiamaculata (Pinto, 1926) from the separation of the common ancestor when the connection between the Amazon Rainforest and the Atlantic Forest was lost as a result of climatic changes caused by the Andean uplift] 4 and agmatoploidy in the X sex chromosome in P. lutzi 2n = 24 (20A + X 1 X 2 X 3 Y). 22 Justi et al 5 . 15 With the exception of T. lecticularia (which was recovered as a sister species to Paratriatoma hirsuta (Barber, 1939), both having karyotype 2n = 22), all the species of the complexes lecticularia and phyllosoma that were cytogenetically studied have karyotype 2n = 23 (20A + X 1 X 2 Y).…”

Do not judge a book by its cover: would Triatoma tibiamaculata (Pinto, 1926) belong to Triatoma Laporte, 1832, or to Panstrongylus Berg, 1879, with misleading homoplasies?

“… X X sex chromosome, Y Y sex chromosome a Crossa et al [ 35 ] b Panzera et al [ 36 ] c Santos et al [ 37 ] d Alevi et al [ 38 ] e Schreiber and Pellegrino [ 39 ] f Panzera et al [ 40 ] g Panzera et al [ 41 ] h Pita et al [ 42 ] i Panzera et al [ 43 ] …”

Trends in Taxonomy of Chagas Disease Vectors (Hemiptera, Reduviidae, Triatominae): From Linnaean to Integrative Taxonomy

“…Cytotaxonomy was started with Ueshima [179] by proposing the application of cytogenetic studies of chromosomes to differentiate morphologically related species. Later, the use of chromosomal analyses-such as karyotypes [180][181][182][183]-the constitutive heterochromatin pattern [156,184,185], the heterochromatin base pair composition [186][187][188], and the location of the nucleolar organizing region [139,156,189], assisted in the correct identification and classification of triatomines. Recently, dichotomous keys have been proposed based on cytogenetic data [190][191][192][193].…”