Karyotype, C-and fluorescence banding pattern, NOR location and FISH study of five Scarabaeidae (Coleoptera) species

Abstract

Meiotic chromosomes obtained from members of the coleopteran subfamilies Rutelinae and Dynastinae were studied using standard and silver nitrate staining, C-banding, base-specific fluorochromes and fluorescent in situ hybridization (FISH). The study presents detailed karyotipic descripitions of three Rutelinae species (Geniates borelli, Macraspis festiva and Pelidnota pallidipennis), and two Dynastinae species (Lygirus ebenus and Strategus surinamensis hirtus) with special emphasis on the distribution and variability of constitutive heterochromatin and the nucleolar organizer region (NOR). We found that for G. borelli, P. pallidipennis, L. ebenus and S. s hirtus the karyotype was 2n = 20 (9II + Xy p ), with G. borelli, P. pallidipennis and L. ebenus showed meta-submetacentric chromosomes which gradually decreased in size. For Macraspis festiva the karyotype was 2n = 18 (8II + Xy p ). In L. ebenus we found that the NOR was located on an autosome, but in the other four species it occurred on the sex bivalents. In all five species the constitutive heterochromatin (CH) was predominantly pericentromeric while the X chromosomes were almost completely heterochomatic, although CMA 3 /DA/DAPI staining showed intra and interspecific variation in the bright fluorescence of the constitutive heterochromatin. The FISH technique showed rDNA sites on the X chromosome of the Rutelinae species.

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 hybridization of the C 0 t-1 DNA fraction confirmed the heterochromatin distribution pattern, indicating the presence of highly and moderately repetitive sequences in these areas. In the Scarabaeidae family and in Coleoptera as a whole, the small blocks of heterochromatin in the pericentromeres represent a conspicuous pattern that has been described in representative organisms from distinct and unrelated families (Moura et al, 2003;Bione et al, 2005a). On the other hand, some species had small additional blocks, as observed in D. geminatus, as was reported in Scarabaeidae (that is, Bubas bison) (Colomba et al, 2006) and Aphodius representative species (Wilson and Angus, 2004).…”

“…Cytogenetic studies in Coleoptera that focus on repetitive sequences are scarce and are frequently restricted to chromosomal banding (C-banding), basespecific fluorochromes and, to a lesser extent, fluorescent in situ hybridization (FISH) using ribosomal DNA (rDNA) or satDNA as probes (Roż ek et al, 2004;Bione et al, 2005a;Palomeque et al, 2005). With the aim of contributing to the knowledge of coleopteran genomes, we investigated the organization of repeated DNA elements in the karyotype of Dichotomius geminatus and described the association of 5S rRNA and histone H3 genes, as well as the characteristics of a newly detected B chromosome.…”

Cytogenetics of the darkling beetles Zophobas aff. confusus and Nyctobates gigas (Coleoptera, Tenebrionidae)

“…confusus, the nucleolar remnant is present until the end of pachytene, while Xyp remains positive for silver nitrate staining until metaphase I. Such a pattern has also been observed in some coleopteran species independent of NOR, irrespective of whether it is associated with Xyp (Postiglioni and Brum-Zorrilla, 1988;Moura et al, 2003;Bione et al, 2005b). This pattern is independent of the occurrence of NORs in the Xyp and can result in the presence of argyrophilic substances in the lumen of that sex bivalent.…”

Karyotypic characterisation and C-banding of representatives from Geotrupinae and Dynamopinae (Coleoptera: Scarabaeidae)

“…This family shows conserved karyotypes with more than 50% of the species presenting the diploid number 2n = 20, Xyp sex mechanism and biarmed chromosomes. This condition has been considered primitive to this group and also to the whole order Coleoptera [3,4,5,6,7,8]. Out of 1,000 species of Geoptrupinae, only 13 species have been cytologically analysed.…”

“…About 70 Scarabaeidae species have so far been subjected to differential or molecular cytogenetic techniques, such as C banding, base-specific fluorochromes, silver nitrate staining or fluorescence in situ hybridization [5,6,7,11,12,13,14]. The constitutive heterochromatin in this family is predominantly located in the pericentric region of the chromosomes.…”