Cytogenetic analyses using C-banding and DAPI/CMA3 staining of four populations of the maize weevil Sitophilus zeamais Motschulsky, 1855 (Coleoptera, Curculionidae)

Abstract

Cytogenetic data avalaible for the maize weevil Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae), one of the most destructive pests of stored cereal grains, are controversial. Earlier studies focused on single populations and emphasized chromosome number and sex determination system. In this paper, the karyotypes of four populations of Sitophilus zeamais were characterized by conventional staining, C-banding and sequential staining with the fluorochromes chromomycin-A3/4-6-diamidino-2-phenylindole (CMA3/DAPI). The analyses of metaphases obtained from the cerebral ganglia of last instar larvae and the testes of adults showed that the species had 2n = 22 chromosomes, with 10 autosomal pairs and a sex chromosome pair (XX in females and Xyp in males). Chromosome number, however, ranged from 2n = 22 to 26 due to the presence of 0–4 supernumerary chromosomes in individuals from the populations of Viçosa, Unai and Porto Alegre. With the exception of the Y chromosome, which was dot-like, all other chromosomes of this species were metacentric, including the supernumeraries. The heterochromatin was present in the centromeric regions of all autosomes and in the centromere of the X chromosome. The B chromosomes were partially or totally heterochromatic, and the Y chromosome was euchromatic. The heterochromatic regions were labeled with C-banding and DAPI, which showed that they were rich in AT base pairs.

Comparative cytogenetics and derived phylogenic relationship among Sitophilus grain weevils (Coleoptera, Curculionidae, Dryophthorinae)

“…As described by Silva et al (2015), the karyotype of this species had 2n = 22 chromosomes. All autosomal chromosomes of this species exhibited metacentric morphology and a gradual reduction in size.…”

“…The coincidence of DAPI staining with the C-banding marks in the chromosomes of S. granarius , S. linearis and S. oryzae , as well as in S. zeamais (Silva et al 2015), demonstrate the occurrence of a higher amount of AT base pairs in the heterochromatic sequences of these species. Positive DAPI signals were present in the majority of weevils previously studied confirming that AT pairs often make up the main part of the heterochromatin in these species (Lachowska 2008, Lachowska et al 2008, Holecová et al 2013).…”

“…A few species of Sitophilus weevils were karyotyped to date, mainly in the 1970’s and 1980’s (Inkmann 1933, cited in Smith and Virkki 1978, Takenouchi 1958, cited in Smith and Virkki 1978, Smith and Brower 1974, Smith and Virkki 1978, Barrion et al 1988, Zhi-Yua et al 1989, Moraes et al 2003, Silva et al 2015). However, the results of these earlier efforts involving grain weevils were discrepant, emphasizing the need for further and more reliable analysis.…”

“…However, the results of these earlier efforts involving grain weevils were discrepant, emphasizing the need for further and more reliable analysis. Only a single recent karyotype analysis of the maize weevil Sitophilus zeamais Motschulsky, 1855 used more refined cytogenetic techniques (Silva et al 2015). Knowledge of genome size is even scarcer, since no data are currently available in the literature for any species of Sitophilus .…”

Molecular cytogenetic studies in the ladybird beetle Henosepilachna argus Geoffroy, 1762 (Coleoptera, Coccinellidae, Epilachninae)

“…Equally in meiotic metaphase I bivalents the pericentromeric regions were intensely stained. DAPI staining coincident with C-banding heterochromatic pericentromeric regions has also been found in some Coleoptera , suggesting that these heterochromatic regions are rich in AT base pairs although in other Coleoptera the DAPI staining of chromosomes did not reveal any positive signal ( Karagyan et al 2012 , Da Silva et al 2015 and references therein). This varied and different banding pattern could be due to the structure and composition of insect heterochromatin, especially in relation to the heterochromatin associated proteins ( Lorite et al 1996b ).…”