C-banding and fluorescent in situ hybridization with rDNA sequences in chromosomes of Cycloneda sanguinea Linnaeus (Coleoptera, Coccinellidae)

Abstract

The aim of this study was to describe mitotic and meiotic chromosomes of Cycloneda sanguinea using C-banding, fluorescent in situ hybridization (FISH) rDNA probes, and sequential FISH/Ag-NOR staining. The chromosome number was 2n = 18 + XX for females and 2n = 18 + Xy for males. The X chromosome was metacentric and the Y chromosome was very small. During meiosis, the karyotypic meioformula was n = 9 + Xy p , and sex chromosomes configured a parachute at metaphase I. At the beginning of pachytene, bivalents were still individualized, and sex chromosomes were associated end-to-end through the heteropycnotic region of the X chromosome. Later in pachytene, further condensation led to the formation of a pseudo-ring by the sex bivalent. All chromosomes showed pericentromeric heterochromatin. FISH and sequential FISH/Ag-NOR staining evidenced the location of the nucleolar organizer region in one pair of autosomes (at spermatogonial metaphase). During meiosis, these genes were mapped to a region outside the sex vesicle by FISH, although Xy p was deeply stained with silver at metaphase I. These results suggest that these argyrophilic substances are of a nucleolar protein nature, and seem to be synthesized by a pair of autosomes and imported during meiosis (prophase I) to the sex pair, during the association of the sex chromosomes.

Cytogenetic markers applied to cytotaxonomy in two soybean pests: Anticarsia gemmatalis (Hübner, 1818) and Chrysodeixis includens (Walker, 1858)

“…The pattern of RONs in the Noctuoidea superfamily is the presence of only an interstitial marking, except for Spodoptera latifascia and S. descoinsi, which present more than one marking [17,41]. A labeling in the nuclei of A. gemmatalis and C. includens confirms that labeling which has been observed in the superfamily that corroborates the karyotypic conservation regarding the number of this sequence; however, due to the difficulty of observing these chromosomes, it was not possible to observe the location of the 18S rDNA in metaphase chromosomes, which made it impossible to determine the position of this site.…”

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

“…C-banding reveals the constitutive heterochromatin ( Sumner 1972 ). In Coccinellidae beetles the heterochromatin is associated with pericentromeric regions and shorts arms of chromosomes ( Drets et al 1983 , Maffei et al 2004 , Rozek and Holecova 2002 , among others). The application of C-banding techniques in Henosepilachna argus showed large heterochromatic pericentromeric blocks on all chromosomes.…”

“…The localization of the nucleolar organizer region (NOR) is unknown in other species of Epilachnini . At this moment the chromosome location of the NOR in Coccinellidae is only known in two species, Olla v-nigrum Mulsant, 1866 and Cycloneda sanguinea Linnaeus, 1763 ( Maffei et al 2001 , 2004 ) by Ag-NOR banding and FISH. The NOR location in both species is variable.…”

“…The NOR location in both species is variable. In the first one the NOR region appears on the sex chromosomes ( Maffei et al 2001 ), nevertheless in the second one the NOR region appears on one pair of autosomes ( Maffei et al 2004 ). The variable location of the NORs has been observed in other Coleopteran families as Carabidae , Melolonthidae , Tenebrionidae or Scarabaeidae that show that rDNA sequences are located on the sex chromosomes, autosomes or both depending on the species ( Oliveira et al 2012 , Arcanjo et al 2013 ).…”