Cytogenetic Analysis of <b><i>Lagria villosa</i></b> (Coleoptera, Tenebrionidae): Emphasis on the Mechanism of Association of the Xy_p Sex Chromosomes

Abstract

The Xy_p sex determination mechanism is the system most frequent and ancestral to Coleoptera. Moreover, the presence of argyrophilous material associated with the sex bivalent is described as being responsible for the maintenance and association of these chromosomes. There are no karyotype data available regarding the genus Lagria and no consensus in the literature regarding the argyrophilous material present in the lumen of sex bivalent. Therefore, the aim of this work was to investigate the mechanism of sex chromosome bivalent association in Lagria villosa by analyzing the argyrophilous nature of the material present in the Xy_p lumen. It was also intended to characterize L. villosa cytogenetically. The analysis of meiotic cells showed 2n = 18 = 16+Xy_p for males and 2n = 18 = 16+XX in females and the meiotic formula was 2n = 8^II+Xy_p. The C-banding showed blocks of pericentromeric heterochromatin in all chromosomes except in the y_p chromosome. In these regions, the use of fluorochromes revealed the presence of heterochromatin containing GC rich DNA sequences. The study of synaptonemal complex showed a gradual increase in the electron-density of the axial elements of the sex chromosomes and their association with strongly electron-dense material. The pepsin pretreatment revealed that the material impregnated by silver is protein.

Karyotype and sex chromosome differentiation in two Nalassus species (Coleoptera, Tenebrionidae)

“…5d). Similar findings on argyrophilic Xy p in metaphase I as well as prophase I were previously reported for several beetles such as Zophobas aff. confusus Gebien 1906 (Tenebrionidae) (Lira- Neto et al 2012), Lagria villosa Fabricius 1781 (Tenebrionidae) (Goll et al 2013), Palembus dermestoides (Tenebrionidae) and Epicauta atomaria Germar 1821 (Meloidae) (Almeida et al 2000). Although, rDNA-FISH studies has shown that these strongly argyrophilic areas in prophase I bivalents are associated with NOR (Juan et al 1993, Bruvo-Madaric et al 2007), the existence of highly impregnated areas on sex chromosomes until metaphase I thought to be related to association and segregation of sex bivalents due to nucleolar material or distinctive heterochromatin (Juan et al 1993, John and Lewis 1960).…”

Chromosome mapping of 28S ribosomal genes in 11 species of Cassidinae (Coleoptera: Chrysomelidae)

“…The images of the chromosomes were taken using a Zeiss Imager A2 equipped with an Axio Cam digital camera, using Axion Vision software (Carl Zeiss AG, Jena, Germany). Silva et al, 2009;Almeida et al, 2010;Cabral de Mello et al, 2010, 2011aMendes-Neto et al, 2010;Oliveira et al, 2010Oliveira et al, , 2012aGiannoulis et al, 2011;Proença et al, 2011;Lira-Neto et al, 2012;Karagyan et al, 2012;Goll et al, 2013Goll et al, , 2015.…”

High-Resolution Physical Chromosome Mapping of Multigene Families in <b><i>Lagria villosa</i></b> (Tenebrionidae): Occurrence of Interspersed Ribosomal Genes in Coleoptera

“…1 C). The analysis of mitotic cells using the 5S rDNA probe showed that 5S is located on the short arm of chromosome 4, coincident with the 45S cistron location described by Goll et al [2013]. Double FISH with 5S and 18S rDNA probes, used to examine the synteny between the 5S and 18S genes, showed that ribosomal clusters are found in only one autosomal pair at metaphase I ( fig.…”

“…Molecular cytogenetic studies of this family remain scarce despite the large number of species. The karyotype, meiosis and 45S rDNA gene location of L. villosa were previously described by Goll et al [2013], with 2n = 18 = 16 + Xy p for males and 2n = 18 = 16 + XX for females. The observed morphology was predominantly submetacentric for autosomal chromosomes and metacentric for the X chromosome; the Y chromosome was difficult to identify.…”