Evolutionary chromosomal differentiation among four species of Conoderus Eschscholtz, 1829 (Coleoptera, Elateridae, Agrypninae, Conoderini) detected by standard staining, C-banding, silver nitrate impregnation, and CMA3/DA/DAPI staining

Abstract

The speciose Brazilian Elateridae fauna is characterized by high karyotypic diversity, including one species (Chalcolepidius zonatus Eschscholtz, 1829) with the lowest diploid number within any Coleoptera order. Cytogenetic analysis of Conoderus dimidiatus Germar, 1839, C. scalaris (Germar, 1824,) C. ternarius Germar, 1839, and C. stigmosus Germar, 1839 by standard and differential staining was performed with the aim of establishing mechanisms of karyotypic differentiation in these species. Conoderus dimidiatus, C. scalaris, and C. ternarius have diploid numbers of 2n(male) = 17 and 2n(female) = 18, and a X0/XX sex determination system, similar to that encountered in the majority of Conoderini species. The karyotype of C. stigmosus was characterized by a diploid number of 2n = 16 and a neoXY/neoXX sex determination system that was highly differentiated from other species of the genus. Some features of the mitotic and meiotic chromosomes suggest an autosome/ancestral X chromosome fusion as the cause of the neoXY system origin in C. stigmosus. C-banding and silver impregnation techniques showed that the four Conoderus species possess similar chromosomal characteristics to those registered in most Polyphaga species, including pericentromeric C band and autosomal NORs. Triple staining techniques including CMA3/DA/DAPI also provided useful information for differentiating these Conoderus species. These techniques revealed unique GC-rich heterochromatin associated with NORs in C. scalaris and C. stigmosus and CMA3-heteromorphism in C. scalaris and C. ternarius.

Comparative cytogenetic analysis in 13 tortoise beetles (Coleoptera: Chrysomelidae: Cassidinae) from Brazil

“…This same pattern was also observed in the autosomal chromosomes of Coleoptera (Virkki, 1983, Schneider et al, 2006Mello et al, 2014). In the sex chromosomes, the heterochromatin can extend to all chromosome arms or is restricted exclusively in the pericentromeric region (Almeida et al, 2000;Rozek et al, 2004).…”

Cytogenetic characterization of Eurysternus caribaeus (Coleoptera: Scarabaeidae): evidence of sex-autosome fusion and diploid number reduction prior to species dispersion

“…The C-banding pattern observed in E. caribaeus is quite common among Scarabaeidae representatives and also to Coleoptera as a whole (Moura et al 2003;Colomba et al 2004Colomba et al , 2006Rozek et al 2004;Wilson and Angus 2004, 2005Bione et al 2005b;Schneider et al 2006). Meanwhile, particular cases of CH distribution have been reported in some Scarabaeidae; Cetonia aurata and Bubas bison have CH blocks located in the terminal region of eight autosomal bivalents, in addition to the pericentromeric blocks (Colomba et al 1996(Colomba et al , 2006Dutrillaux et al 2006).…”

“…In Coleoptera, examples of diploid number reduction and/or neo-XY origin were observed in Elateridae, Conoderus stigmosus (2n = 16, neo-XY), Lampyridae, Bicellonycha lividipennis (2n = 18, neo-XY) and other families (Schneider et al 2006;Dias et al 2007). This pattern of chromosomal evolution in insects has also been seen in other orders, for e.g., Heteroptera (Bressa et al 1999), Odonata (Mola and Papeschi 1994), and to arthropods in general in spiders (Rezac et al 2006) and pseudoscorpions (Stahlavsky and Kral 2004).…”

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

“…However, numeric and morphologic variation in chromosomes of different taxa, for example, in families and subfamilies, have been described in the literature. Different structural rearrangements such as Robertsonian rearrangements and in tandem fusions and fissions can be responsible for such variations (Smith and Virkki, 1978;Vidal and Nocera, 1984;Petitpierre et al, 1991;Schneider et al, 2006;Moura et al, 2008;Cabral-de-Mello et al, 2008). The 2 species described herein differed with regard to the diploid number, chromosomal morphology, and sex chromosome bivalent.…”

“…Therefore, the origin of the neoXY system in the tenebrionid Pimelia sparsa sparsa (8 + neoXY) has been thought to result from a rearrangement involving the ancient Xyp with loss of most of the existent heterochromatin in the X chromosome (Pons, 2004). Schneider et al (2006) also suggested that the fusion of autosomal/Xy chromosome might be responsible for the origin of the 7 + neoXY karyotype in Conoderus stigmosus (Elateridae).…”