Cytogenetic, morphological and molecular characterization of two cryptic species of the genus Omophoita Chevrolat, 1837 (Coleoptera: Chrysomelidae: Galerucinae)

Giant Sex Chromosomes in Omophoita Species (Coleoptera, Chrysomelidae): Structural and Evolutionary Relationships Revealed by Zoo-FISH and Comparative Genomic Hybridization (CGH)

“…The diploid numbers found in the species herein analyzed are in accordance with the previous ones described by Almeida, Campaner, and Cella [ 13 ]. Most Oedionychina species maintain the same karyotype composition with few exceptions [ 11 , 16 , 26 , 27 ]. All Oedionychina species share giant sex chromosomes, and there are some variations of this system, such as for Asphaera , which has just one giant Y chromosome and many X chromosomes (Xn + Y) [ 26 ].…”

“…On the other hand, because changes in genomic architecture are known to accumulate over time, sex chromosomes that have developed over a long period can have a considerably higher amount of genomic divergence [ 45 , 55 , 56 , 57 , 58 ]. The fusion process is supported by the presence of interstitial telomeric site (ITS) signals found in Alagoasa [ 15 ] and Omophoita [ 27 ] species, indicating that chromosome fusions may have occurred before the growth of Oedionychina giant sex chromosomes. Indeed, high genomic similarities between the similarly sized X and Y chromosomes of Omophoita species, as demonstrated by our WCP research, support this hypothesis ( Figure 3 ).…”

“…Indeed, high genomic similarities between the similarly sized X and Y chromosomes of Omophoita species, as demonstrated by our WCP research, support this hypothesis ( Figure 3 ). This process of fusion between Oedionychina’s sex chromosomes may be related to the decrease in chromosome number in this group because in Chrysomelidae, having 2n = 24 chromosomes is considered a plesiomorphic feature, whereas in Oedionychina, 2n = 22 is considered a plesiomorphic feature [ 27 , 33 ].…”

“…Among the groups of Coleoptera that have been cytogenetically analyzed, the flea beetles Alticinae are considered derived, since they have a karyotype that varies in terms of chromosome number and sex determination system [ 11 , 12 ]. Within Alticinae, “Oedionychina” (Oedionychini sensu Chapuis 1875) is the subtribe whose cytogenetics have been most studied, given the presence of giant sex chromosomes [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. However, the group’s phylogenetic relationships have not been resolved because of their diversity; most studies are limited and do not include all available species [ 28 , 29 ].…”

“…Oedionychina is an insect group known to have giant sex chromosomes that are significantly larger than autosomes, making it an exceptional group [ 33 ]. Most Oedionychina species present a conserved diploid number (2n = 22 = 10II + X + y) [ 7 , 11 , 13 , 14 , 15 , 27 , 34 ]. Conventional cytogenetic analysis (Giemsa stain, Ag-NOR) and the mapping of the ribosomal cluster rDNA 45S and 5S have shown that there is little variation between species concerning the loci of these markers [ 10 , 13 , 15 , 19 , 34 , 35 ].…”