Comparative cytogenetics of three species of Dichotomius (Coleoptera, Scarabaeidae)

Abstract

Meiotic and mitotic chromosomes of Dichotomius nisus, D. semisquamosus and D. sericeus were analyzed after conventional staining, C-banding and silver nitrate staining. In addition, Dichotomius nisus and D. semisquamosus chromosomes were also analyzed after fluorescent in situ hybridization (FISH) with an rDNA probe. The species analyzed had an asymmetrical karyotype with 2n = 18 and meta-submetacentric chromosomes. The sex determination mechanism was of the Xy p type in D. nisus and D. semisquamosus and of the Xy r type in D. sericeus. C-banding revealed the presence of pericentromeric blocks of constitutive heterochromatin (CH) in all the chromosomes of the three species. After silver staining, the nucleolar organizer regions (NORs) were located in autosomes of D. semisquamosus and D. sericeus and in the sexual bivalent of D. nisus. FISH with an rDNA probe confirmed NORs location in D. semisquamosus and in D. nisus. Our results suggest that chromosome inversions and fusions occurred during the evolution of the group.

Chromosomal mapping of repetitive DNAs in the beetle Dichotomius geminatus provides the first evidence for an association of 5S rRNA and histone H3 genes in insects, and repetitive DNA similarity between the B chromosome and A complement

“…The karyotype is 2n ¼ 18,Xy p and the metacentric, submetacentric and subacrocentric chromosomes in this species are in concordance with the previous description by Cabral-de-Mello et al (2008), and this karyotypic formula has been described for some other species of Dichotomius (Silva et al, 2009).…”

“…On the other hand, our results show that, at least in D. geminatus, the origin of the B chromosome is not related to the autosomal fusion process that occurred in this species. This information is corroborated by the absence of supernumerary elements in some other species from the genus that has the same macro chromosome pair, resulting from fusion, that was observed in D. geminatus (2n ¼ 18,Xy p ) (Silva et al, 2009).…”

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

“…The species with interstitial and/or centromeric rDNA cistrons are mainly members of the families Scarabaeidae and Chrysomelidae (subfamily Alticinae). As recorded in the present study, the changes in the location of the sites of rDNA are described in species with similar karyotype characteristics (Virkki, 1983;Yadav et al, 1992;Bione et al, 2005;Almeida et al, 2006Almeida et al, , 2010Arcanjo et al, 2009Arcanjo et al, , 2013Silva et al, 2009;Cabral de Mello et al, 2010, 2011bOliveira et al, 2010Oliveira et al, , 2012b. The differences in the location of rDNA in closely related species with similar chromosomal characteristics may be a result of small chromosomal rearrangements, which change the position of the ribosomal site without modifying the metacentric chromosomal morphology.…”

“…Among the Polyphaga, most of the data on the distribution of rDNA is for the family Scarabaeidae, with more than 120 species characterized to date. The occurrence of two autosomal NORs is also widespread within this family, but closely related species do differ in the presence of a ribosomal cluster on more than one autosomal pair and/or on sex chromosomes (Colomba et al, 2006;Silva et al, 2009;Cabral-Mello et al, 2010, 2011aOliveira et al, 2010Oliveira et al, , 2012b.…”

“…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.…”