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

Abstract

ISSN (online): 1802-8829http://www.eje.cz fi nding was corroborated by a phylogenetic study using molecular data (Gómez-Zurita et al., 2008).Cytogenetically, only 117 Cassidinae species belonging to 13 tribes have been investigated to date (for revision see De Julio et al., 2010). The tortoise beetles are considered as a group with conserved karyotype, in which approximately 52% of the analyzed species showed 2n = 16 + Xy p , with metacentric and/or submetacentric chromosomes (De Julio et al., 2010). However, cytogenetic records also demonstrated that the diploid numbers can range from 2n = 16 to 2n = 51, as well the sex chromosome systems, which can be either simple -Xy p , X0, Xy, Xy c , Xy r , neoXY, or multiple -Xyy p , X p neoXneoY p , X p neoXneoy p , neoX p neoyy p , neoX p1 neoX p2 neoXneoy p , neoX p1 neoX p2 neoXneoy, X p1 X p2 -neoXneoy (for review see De Julio et al., 2010). These variations in the diploid number and sex chromosome systems are more or less frequent according to the tribe considered. In Cassidini and Mesomphaliini, 44% and 100% Abstract. In the present work, we have characterized the chromosomes of 13 Cassidinae beetles, belonging to four tribes, the broad aim being to increase the cytogenetic data and establish the mechanisms involved in chromosome evolution of this subfamily, which appear to be conserved karyotypically, i.e. 2n = 16 + Xy p . The analysis of mitotic and meiotic cells revealed a high diversity of diploid numbers (2n = 18, 2n = 22, 2n = 26, 2n = 32, 2n = 36, 2n = 40, 2n = 42), and the presence of sex chromosome system of the Xy p type in most species, with the exception of two representatives that exhibited Xy r and XY systems. C-banding showed constitutive heterochromatin predominantly localized in the pericentromeric region of the chromosomes, but differences regarding the number of chromosomes with positive C-bands, intensity of the blocks, and presence of additional bands in autosomes and/or sex chromosomes were observed among the species investigated. Our data revealed that the karyotype 2n = 16 + Xy p does not occur in all 13 tribes of the Cassidinae characterized cytogenetically, seeming to be only a shared feature among the species of the Cassidini. Variations in the C-band pattern, mainly in closely related species, suggest that the interspecifi c karyotype diversifi cation occurred as a result of changes in the quantity and distribution of constitutive heterochromatin. The occurrence of the Xy p sex chromosome system in the tribe Mesomphaliini, which showed the highest diversity of simple and multiple systems among the coleopteran as a whole, reinforces the view that derived systems originated by chromosome rearrangements involving the Xy p ancestral system.

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

“…sexpunctata, D. cruciata and M. optata, and two Mesomphaliini species: Che. cribraria and P. fl ava, confi rmed the diploid number and the sex chromosome system previously described for these species (Lopes et al, 2016). For the two species of Cassidini, characterized here for the fi rst time, only M. stigmatica (2n = 20 + Xy p ) had a diploid number greater than those recorded for the other species in this genus: M. aciculata, M. gnata, M. optata and M. quadrata (Lopes et al, 2016;this work).…”

“…For the two species of Cassidini, characterized here for the fi rst time, only M. stigmatica (2n = 20 + Xy p ) had a diploid number greater than those recorded for the other species in this genus: M. aciculata, M. gnata, M. optata and M. quadrata (Lopes et al, 2016;this work). This increase in the diploid number may correspond to a derived condition within the genus Microctenochira and even in the tribe Cassidini, taking into account that approximately 60% of the species in this tribe, belonging to 11 distinct genera, have a diploid number 2n = 18 (De Julio et al, 2010;Lopes et al, 2016).…”

“…Among the 14 tribes of Cassidinae cytogenetically characterized, the Cassidini and Mesomphaliini are the most homogenous and variable in terms of karyotypes, respectively. In this latter tribe, the karyotype variability probably refl ects its non-monophyletic nature (Chaboo, 2007;Lopes et al, 2016).…”

“…The chromosomal preparations were obtained from testes of adult individuals, following the method of Lopes et al (2016). Total genomic DNA of Charidotella immaculata (Olivier, 1790) was extracted from the abdomen using the DNeasy Blood & Tissue Kit (Qiagen, Hilden, Germany).…”

“…comprises approximately 6,000 species in 43 tribes (Chaboo, 2007). Cytogenetically, only 124 species, grouped in 14 tribes, have been studied, of which 52% of the species have the conserved karyotype 2n = 16 + Xy p , with biarmed chromosomes (De Julio et al, 2010;Lopes et al, 2016). Among the 14 tribes of Cassidinae cytogenetically characterized, the Cassidini and Mesomphaliini are the most homogenous and variable in terms of karyotypes, respectively.…”