Expanding the Chromosomal Evolution Understanding of Lygaeioid True Bugs (Lygaeoidea, Pentatomomorpha, Heteroptera) by Classical and Molecular Cytogenetic Analysis

Abstract

The Lygaeoidea comprise about 4660 in 790 genera and 16 families. Using standard chromosome staining and FISH with 18S rDNA and telomeric (TTAGG)n probes, we studied male karyotypes and meiosis in 10 species of Lygaeoidea belonging to eight genera of the families Blissidae, Cymidae, Heterogastridae, Lygaeidae, and Rhyparochromidae. Chromosome numbers were shown to range from 12 to 28, with 2n = 14 being predominant. All species have an XY system and all but one has a pair of m-chromosomes. The exception is Spilostethus saxatilis (Lygaeidae: Lygaeinae); in another species of Lygaeinae, Thunbergia floridulus, m-chromosomes were present, which represent the first finding for this subfamily. All species have an inverted sequence of sex chromosome divisions (“post-reduction”). The 18S rDNA loci were observed on one or both sex chromosomes in Kleidocerys resedae and Th. floridulus, respectively (Lygaeidae), while on an autosomal bivalent in all other species. The rDNA loci tended to be close to the end of the chromosome. Using (TTAGG)n—FISH, we were able to show for the first time that the Lygaeoidea lack the canonical “insect” telomere motif (TTAGG)n. We speculate that this ancestral motif is absent from the entire infraorder Pentatomomorpha being replaced by some other telomere repeat motif sequences.

Karyotype diversity in the genus Nysius Dallas, 1852 (Hemiptera, Heteroptera, Lygaeidae) is much greater than you might think

“…The above hypothesis is confirmed by the fact that in the karyotype with 2n = 14 there is a pair of very large chromosomes (although for many species no karyotype illustration is given in the original publications), whereas in the karyotype with 2n = 22 (in both N. graminicola and N. tennellus) there is no such pair, and the chromosomes form a decreasing size series. The detection of a ribosomal cluster in autosomes in N. cymoides and N. helveticus sharing a modal karyotype (Golub et al 2023) suggests an autosomal rDNA pattern to be the ancestral state for Nysius. Because the 18S ribosomal genes in these species are located on the largest pair of autosomes, we hypothesized that they would be found in one of the autosome pairs in N. graminicola with a derived karyotype.…”

“…Data on the number of chromosomes, the mechanism of sex chromosomes and, in some cases, the peculiarities of meiosis are currently available for 24 species, i.e. about 25% of all known species of this genus (reviewed by Ueshima and Ashlock 1980 ; see also Golub et al 2023 ). Routine cytogenetics of Nysius appears to be highly conserved: all species have 2n = 14(12+XY), with the only exception being N. tennellus Barber, 1947, which has 2n = 22(20+XY).…”

“…rRNA genes are among the better-known multigene families in true bugs ( Panzera et al 2021 ; Kuznetsova et al 2021 ). The first recent application of FISH to map rRNA genes on the chromosomes of two Nysius species with modal karyotypes of 2n = 14(12+XY), N. cymoides (Spinola, 1837) and N. helveticus (Herrich-Schäffer, 1850), showed that they both have rDNA sites on the largest pair of autosomes ( Golub et al 2023 ).…”

The spread of satellite DNAs in euchromatin and insights into the multiple sex chromosome evolution in Hemiptera revealed by repeatome analysis of the bug Oxycarenus hyalinipennis

“…This approach has allowed the characterization of satDNAs in the genomes of numerous non-model species from different groups. For example, satDNAs have been studied in insects (Anjos et al, 2023;Cabral-de-Mello et al, 2021;Mora et al, 2020;Pita et al, 2017), mollusks (Tunji c-Cvitani c et al, 2021, fishes (Goes et al, 2022;Kretschmer et al, 2022), frogs (da Silva et al, 2020da Silva et al, 2023), mammals (Gutiérrez et al, 2022) and plants (Heitkam et al, 2021;Sader et al, 2021). Consequently, lowabundance satDNAs have been characterized, and some of them have been found in euchromatin (Cabral- Milani et al, 2021;Montiel et al, 2021;Pita et al, 2017).…”