Navegando por Autor "Barros, Luísa Antônia Campos"

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Banding patterns of three leafcutter ant species of the genus Atta (Formicidae: Myrmicinae) and chromosomal inferences
(Florida Entomologist, 2014-12) Barros, Luísa Antônia Campos; Teixeira, Gisele Amaro; Aguiar, Hilton Jeferson Alves Cardoso de; Mariano, Cléa Dos Santos Ferreira; Delabie, Jacques Hubert Charles; Pompolo, Silvia das Graças
Among Neotropical ants, the genera Acromyrmex and Atta are of great importance because they include the major agricultural pest species. Regarding the genus Atta, considered one of the most derived of the tribe Attini, cytogenetic data exists for 5 taxa that present 2n = 22 chromosomes; however, information regarding banding patterns is only available for Atta colombica. Cytogenetics has contributed to several aspects related to the family Formicidae, in particular to the understanding of its evolution. Therefore, the aim of this study was to increase the cytogenetic data on Atta sexdens rubropilosa, Atta laevigata and Atta bisphaerica belonging to populations in the state of Minas Gerais, Brazil. The 3 species were characterized as having 2n = 22 chromosomes with a karyotypic formula of 2n = 18m 2sm 2st. Using the C-banding technique, small heterochromatic markings were observed in the centromeres of most of the chromosomes. The presence of GC-rich blocks in the interstitial region on the long arm of the fourth pair of metacentric chromosomes was indicated by CMA3 fluorochrome. The data from this study enabled a comparison with Acromyrmex striatus, a phylogenetically close species possessing the same chromosome number as the Atta species studied in this work, although clear differences were evident in the morphologies of 2 chromosome pairs and in the distribution and composition of heterochromatin. These results show the constancy of the chromosome number, morphology and banding pattern for the species studied, highlighting the importance of measuring the chromosomes to enable accurate comparison and using banding techniques to compare species of genera with a conserved chromosome number.
Citogenética de espécies de Attini (Formicidae: Myrmicinae)
(Universidade Federal de Viçosa, 2010-07-19) Barros, Luísa Antônia Campos; Souza, Danival José de; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4702164J6; Lúcia, Terezinha Maria Castro Della; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783306E2; Pompolo, Silvia das Graças; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4780564A2; http://lattes.cnpq.br/3102759229194899; Costa, Marco Antonio; http://lattes.cnpq.br/8721647772738636; Santos, Jorge Abdala Dergam dos; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4780131D9
A tribo Attini é um grupo monofilético que inclui mais de 230 espécies agrupadas em 14 gêneros. Nesta tribo estão incluídas as formigas cortadeiras (Atta e Acromyrmex), consideradas importantes pragas agrícolas. A utilização da citogenética na família Formicidae tem mostrado importante contribuição nas mais de 750 espécies de formigas estudadas. Os dados citogenéticos são reportados para 10% das espécies da tribo Attini. O presente trabalho teve como objetivo o estudo citogenético de seis espécies do gênero Acromyrmex e de sete espécies de Attini distribuídas em quatro gêneros: Apterostigma, Mycocepurus, Sericomyrmex e Trachymyrmex. Parte das espécies foi submetida a técnicas de bandamentos cromossômicos. Os cariótipos observados foram: Apterostigma madidiense Weber (n=23, 7m + 10sm + 5st + 1a), A. steigeri Santschi (2n=22, 20m + 2sm), Mycocepurus goeldii (Forel) (2n=8, 4m + 4sm), Sericomyrmex sp. (2n=50, 44m + 6sm; n=25, 22m + 3sm), Trachymyrmex fuscus Emery (2n=18, 16m + 2sm; n=9, 8m + 1sm), T. relictus Borgmeier (2n=20m, n=10m) e Trachymyrmex sp. (2n=22, 18m + 4sm). Trachymyrmex fuscus apresentou polimorfismo de tamanho no braço curto do par submetacêntrico. As possíveis causas da duplicação do segmento cromossômico são discutidas. As seis espécies do gênero Acromyrmex apresentaram 2n=38 cromossomos. Cada espécie mostrou um cariótipo diferente em relação à morfologia (A. balzani: 12m + 10sm + 14st + 2a; A. coronatus: 12m + 12sm + 12st + 2a; A. disciger: 10m + 12sm + 14st + 2a; A. niger: 12m + 18sm + 6st + 2a; A. rugosus: 16m + 12sm + 8st + 2a; A. echinatior: 8m + 6sm + 14st + 10a) e variações na distribuição de heterocromatina (banda C) e regiões ricas em GC (CMA3). Em três espécies (A. coronatus, A. disciger, A. niger) o par subtelocêntrico de maior tamanho foi o portador de genes ribossomais. As espécies do gênero Acromyrmex apresentaram estabilidade no número cromossômico com diferenças no cariótipo. Isto sugere que rearranjos do tipo translocações, crescimento de heterocromatina e inversão devem ter ocorrido durante a evolução das espécies deste gênero, levando a modificações nos cariótipos das diferentes espécies.
Comparative physical mapping of 18S rDNA in the karyotypes of six leafcutter ant species of the genera Atta and Acromyrmex (Formicidae: Myrmicinae)
(Genetica, 2017-06-03) Teixeira, Gisele Amaro; Barros, Luísa Antônia Campos; Aguiar, Hilton Jeferson Alves Cardoso de; Pompolo, Silvia das Graças
Leafcutter ants of the Atta and Acromyrmex genera are important plagues in different cultures. Cytogenetic data on chromosome number, morphology, and chromosomal banding pattern are only available for 17 species of leafcutter ants. Molecular cytogenetic data for the detection of ribosomal genes by the FISH technique are scarce, and only 15 Neotropical ant species have been studied. This study aimed to physically map the 18S ribosomal RNA genes (rDNA) of six leafcutter ants belonging to the genera Atta and Acromyrmex using FISH. The results were compared with data on the fluorochrome CMA3 currently available for these species. All analyzed species presented the 18S rDNA on one pair of chromosomes. In Acromyrmex subterraneus molestans and Ac. aspersus, FISH signals were observed in the terminal region of the short arm of the largest subtelocentric pair, while in Atta bisphaerica, A. laevigata, and A. sexdens, FISH signals were observed in the interstitial region of the long arm of the fourth metacentric pair. In Acromyrmex striatus, 18S rDNA was located in the interstitial region of the second metacentric pair. The karyotypic formula for Ac. aspersus was 2n = 38 (8m + 10sm + 16st + 4a), representing the first report in this species. The observed 18S rDNA regions in A. laevigata, A. sexdens, A. bisphaerica, Ac. aspersus, and Ac. subterraneus molestans corresponded to the CMA3 + bands, while in Ac. striatus, several GC-rich bands and one pair of 18S rDNA bands were observed. No differential bands were visible using the DAPI fluorochrome. Karyotype uniformity with previously studied Atta spp. was also observed at the level of molecular cytogenetics using 18S rDNA FISH. A difference in the size of the chromosomal pair carrying the 18S rDNA gene was observed in Ac. striatus (2n = 22) and Atta spp. (2n = 22) highlighting the dissimilarity between these species. The results from the present study contribute to the description of 18S rDNA clusters in Neotropical ants.
Cytogenetic data on six leafcutter ants of the genus Acromyrmex Mayr, 1865 (Hymenoptera, Formicidae, Myrmicinae): insights into chromosome evolution and taxonomic implications
(Comparative Cytogenetics, 2016-05-11) Barros, Luísa Antônia Campos; Aguiar, Hilton Jeferson Alves Cardoso de; Mariano, Cléa dos Santos Ferreira; Andrade-Souza, Vanderly; Costa, Marco Antonio; Delabie, Jacques Hubert Charles; Pompolo, Silvia das Graças
Cytogenetic data for the genus Acromyrmex Mayr, 1865 are available, to date, for a few species from Brazil and Uruguay, which have uniform chromosome numbers (2n = 38). The recent cytogenetic data of Acromyrmex striatus (Roger, 1863), including its banding patterns, showed a distinct karyotype (2n = 22), similar to earlier studied Atta Fabricius, 1804 species. Karyological data are still scarce for the leafcutter ants and many gaps are still present for a proper understanding of this group. Therefore, this study aimed at increasing cytogenetic knowledge of the genus through the characterization of other six species: Acromyrmex balzani (Emery, 1890), Acromyrmex coronatus Fabricius, 1804, Acromyrmex disciger (Mayr, 1887), Acromyrmex echinatior (Forel, 1899), Acromyrmex niger (Smith, 1858) and Acromyrmex rugosus (Smith, 1858), all of which were collected in Minas Gerais – Brazil, except for Acromyrmex echinatior which was collected in Barro Colorado – Panama. The number and morphology of the chromosomes were studied and the following banding techniques were applied: C-banding, fluorochromes CMA3 and DAPI, as well as the detection of 45S rDNA using FISH technique. All the six species had the same chromosome number observed for already studied species, i.e. 2n = 38. Acromyrmex balzani had a different karyotype compared with other species mainly due to the first metacentric pair. The heterochromatin distribution also showed interspecific variation. Nevertheless, all the studied species had a pair of bands in the short arm of the first subtelocentric pair. The fluorochrome CMA3 visualized bands in the short arm of the first subtelocentric pair for all the six species, while Acromyrmex rugosus and Acromyrmex niger also demonstrated in the other chromosomes. The AT-rich regions with differential staining using DAPI were not observed. 45S ribosomal genes were identified by FISH in the short arm of the first subtelocentric pair in Acromyrmex coronatus, Acromyrmex disciger and Acromyrmex niger. The uniform chromosome number in the genus Acromyrmex (2n = 38) suggests that Acromyrmex striatus (2n = 22) should be transferred to a new genus. Other aspects of the chromosome evolution in ants are also discussed.
Cytogenetic studies on populations of Camponotus rufipes (Fabricius, 1775) and Camponotus renggeri Emery, 1894 (Formicidae: Formicinae)
(PLoS One, 2017-05-16) Aguiar, Hilton Jeferson Alves Cardoso de; Barros, Luísa Antônia Campos; Alves, Danúbia Rodrigues; Mariano, Cléa dos Santos Ferreira; Delabie, Jacques Hubert Charles; Pompolo, Silvia das Graças
Two valid ant species, Camponotus rufipes and Camponotus renggeri, have recently been the subject of a broad discussion with reference to taxa synonymization. Both species are quite common among the Neotropical myrmecofauna and share some unique traits, such as the shape of the scape and the pilosity patterns of the tibiae and scapes. A single morphological trait can help distinguish these species; however, only a combination of different approaches can enlighten our view of the complex phylogenetic relationships prevailing in the different populations of these two taxa. Therefore, focusing on the taxonomic issues concerning these two species, a cytogenetic survey including 10 populations of C. rufipes and two populations of C. renggeri was performed. In order to better understand the extent of the relationship between C. rufipes and C. renggeri, two common Neotropical Camponotus species, C. atriceps and C. cingulatus were taken as outgroups. All four species of Camponotus that were studied had 2n = 40 chromosomes (4sm+34st+2t); however, the abundance of chromosome rearrangements observed, combined with several chromosome markers, suggest that C. rufipes and C. renggeri are two good distinct species although closely related. The already reported chromosome translocation 2n = 39 (1m+4sm+32st +2t) for C. rufipes has been found in different populations as in the unprecedented chromosome inversions found both in C. rufipes and in C. renggeri populations. Within the C. renggeri chromosome inversions, both the heterozygous state 2n = 40 (1m+3sm+34st+2t) and the homozygous state, 2n = 40 (2m+2sm+34st+2t) were identified. However, only het- erozygous specimens for chromosome inversions were found among C. rufipes, with karyotype configurations distinct from those found in C. renggeri, with 2n = 40 (1m+4sm+34st +2t). None of the populations studied showed signs of mosaic individuals. With respect to rDNA clusters, the 18S rDNA seemed to be more restricted inside the genome, as C. renggeri showed four 18S rDNA clusters, whereas, C. rufipes, C. atriceps, and C. cingulatus showed only two clusters. The chromosome locations of the 5S rDNA clusters were pointed for the first time in Formicidae, and showed itself to be more widely spread over the genome. By combining different chromosome banding approaches it was possible to demonstrate the crucial importance that chromosome inversions played on the karyotype evolution within these ants. The results also showed that chromosome translocations might be a consequence of the chromatin dynamic condition observed among Camponotus species. The homozygosis condition found in a C. renggeri from a Brazilian savanna population for chromosome inversions and the contrasting heterozygous condition for a different kind of chromosome inversion in C. rufipes from the Brazilian coastal rainforest, opens the window for a chromosome race hypothesis within the group C. renggeri and C. rufipes. The wide distribution, rich ecological interactions, genetic diversity, and morphological variability among C. renggeri and C. rufipes justify questioning of the actual taxonomic status of these species. The answer of this puzzle is clear when observing the number of 18S rDNA clusters of these ants, as C. rufipes has only two clusters whereas C. renggeri has four.
First cytogenetic characterization of a species of the arboreal ant genus Azteca Forel, 1978 (Dolichoderinae, Formicidae)
(Comparative Cytogenetics, 2012-03-16) Cardoso, Danon Clemes; Cristiano, Maykon Passos; Barros, Luísa Antônia Campos; Lopes, Denilce Meneses; Pompolo, Silvia das Graças
In this paper we present, for the first time, a detailed karyotype characterization of a species of the genus Azteca (Dolichoderinae, Formicidae). Cerebral ganglia from Azteca trigona Emery, 1893 were excised and submitted to colchicine hypotonic solution and chromosomal preparations were analyzed through conventional staining with Giemsa, C-banding, silver nitrate staining (AgNO3) and sequential base-specific fluorochromes. The analysis shows that Azteca trigona has a diploid number of 28 chromosomes. The karyotype consists of five metacentric pairs, seven acrocentric pairs and two pseudo-acrocentric pairs, which represents a karyotype formula 2K= 10M + 14A + 4AM and a diploid number of the arms 2AN = 38. The analysis of heterochromatin distribution revealed a positive block on distal region of the short arm of fourth metacentric pair, which was coincident with Ag-NOR band and CMA3 fluorochrome staining, meaning that rDNA sequences are interspaced by GC-rich base pairs sequences. The C-banding also marked short arms of other chromosomes, indicating centric fissions followed by heterochromatin growth. The karyotype analysis of Azteca trigona allowed the identification of cytogenetic markers that will be helpful in a difficult taxonomic group as Azteca and discussion about evolutionary aspects of the genome organization.
The first cytogenetic data on Strumigenys louisianae Roger, 1863 (Formicidae: Myrmicinae: Dacetini): o the lowest chromosome number in the hymenoptera of the neotropical region
(PLOS One, 2014-11-07) Barros, Luísa Antônia Campos; Chaul, Júlio Cézar Mário; Pompolo, Silvia das Graças; Alves-Silva, Ana Paula
In the present study, the first cytogenetic data was obtained for the ant species Strumigenys louisianae, from a genus possessing no previous cytogenetic data for the Neotropical region. The chromosome number observed was 2n = 4, all possessing metacentric morphology. Blocks rich in GC base pairs were observed in the interstitial region of the short arm of the largest chromosome pair, which may indicate that this region corresponds to the NORs. The referred species presented the lowest chromosome number observed for the subfamily Myrmicinae and for the Hymenoptera found in the Neotropical region. Observation of a low chromosome number karyotype has been described in Myrmecia croslandi, in which the occurrence of tandem fusions accounts for the most probable rearrangement for its formation. The accumulation of cytogenetic data may carry crucial information to ensure deeper understanding of the systematics of the tribe Dacetini.
Occurrence of pre-nucleolar bodies and 45S rDNA location on the chromosomes of the ant Mycocepurus goeldii (Forel) (Formicidae, Myrmicinae, Attini)
(Hereditas, 2011-12-21) Barros, Luísa Antônia Campos; Aguiar, Hilton Jeferson Alves Cardoso De; Andrade-Souza, Vanderly; Mariano, Cléa Dos Santos Ferreira; Delabie, Jacques Hubert Charles; Pompolo, Silvia Das Graças
The ant Mycocepurus goeldii (Forel) is known for having a relict karyotype with low chromosome number and the present study help the understanding of this ant cytogenetics by describing the occurrence of pre-nucleolar bodies in their chromosomes using impregnation with silver nitrate (Ag-NOR) and the location of 45S rDNA sites by means of the FISH (fluorescent in situ hybridization) technique. Several spots were observed surrounding all chromosomes when submitted to the Ag-NOR technique. These unusual markings were observed in both chromatids of metaphase and early anaphase chromosomes, and are associated to the presence of pre-nucleolar bodies, allowing the observation of the phenomenon of nucleologenesis. Although recent studies have shown that all chromosomes of M. goeldii exhibit centromeric or pericentromeric markings for the CMA3 fluorochrome, the FISH technique indicated the presence of 45S rDNA in only one pair of chromosomes that differed in the number of CMA3 markings observed for this species, pointing that the other markings observed with this fluorochrome do not match the sequences in ribosomal genes.