Blattodea Karyotype Database

Jankásek, Marek; Varadínová, Zuzana Kotyková; Šťáhlavský, František

doi:10.14411/eje.2021.020

Cited by 8 publications

(7 citation statements)

References 70 publications

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“…[22][23][24][25][26][27][28] As regards any possible role played by GS in diversifying the Blattodea species, the picture we now have for cockroach GS values is a scattered distribution throughout the families, with some very large GS values present together with smaller values within each family. In the light of the new GS data, we speculate that GS exhibits a moderate (positive) correlation with the 2n chromosome number: 18 from minimum GS values at around 2 pg with 2n 23-24 up to 3.2 pg associated with 2n 73-74 (as detailed in the Results section). To support or refute this hypothesised correlation, many more GS data and 2n numbers are needed in order to be able to carry out a rigorous statistical analysis.…”

Section: Speciesmentioning

confidence: 73%

“…At present, it is not possible to infer any correlation between maximum and minimum GS values and the systematics allocation of the species considered given both the paucity of the current data and the fact that there are statistically significant mean GS differences both within and intra-systematic groups. However, Table 1 reports the 2n chromosome number 18 for the species we considered. It does seem that there is a moderate correlation between increasing 2n chromosome number and increasing GS values within the cockroaches species we analyzed: 2n 23 -24 (2.09, 2.20); 2n 33-34 and 37 (2.80, 2.65, 2.65); 2n 47 -48 (2.95); 2n 73 -74 (3.24, 3.23).…”

Section: Resultsmentioning

confidence: 99%

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Genome size evaluations in cockroaches: new entries

2022

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In this paper, we report genome size (GS) values for nine cockroaches (order Blattodea, families Blattidae, Blaberidae and Ectobiidae, ex Blattelidae,), three of which are original additions to the ten already present in the GS database: the death’s head roach (Blaberus craniifer), the Surinam cockroach (Pycnoscelus surinamensis) and the Madeira cockroach (Leucophaea maderae). Regarding the American cockroach (Periplaneta americana), the GS database contains two contrasting values (2.72 vs 3.41 pg); likely, the 2.72 pg value is the correct one as it is strikingly similar to our sperm DNA content evaluation (2.80 ± 0.11 pg). Also, we suggest halving the published GS of the Argentine cockroach Blaptica dubia and the spotted cockroach (the gray cockroach) Nauphoeta cinerea discussing (i) the occurrence of a correlation between increasing 2N chromosome number and GS within the order Blattodea; and (ii) the possible occurrence of a polyploidization phenomenon doubling a basic GS of 0.58 pg of some termite families (superfamily Blattoidea, epifamily Termitoidae).

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Section: Speciesmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Genome size evaluations in cockroaches: new entries

2022

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“…The chromosome numbers of both termite species ( M. bellicosus , 2n = 42 and for C. secundus , 2n = 40) are typical for termites, although variation exists between taxa (Jankásek et al 2021). These values do not differ from those observed in Hymenoptera, which have a similar range (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Data from a wide range of taxa indicate that at least one crossover per chromosome tetrad is essential for correct chromosomal segregation during meiosis. The chromosome numbers M. bellicosus and C. secundus are 2n = 42 and 2n = 40 respectively (Jankásek et al 2021). Considering the assembly lengths, this corresponds to a minumum average genomic recombination rate of 0.92 cM/Mb and 1.01 cM/Mb would be necessary for accurate meiosis to occur in the two species respectively.…”

Section: Low Recombination Rates In Termitesmentioning

confidence: 99%

Unexpectedly low recombination rates and presence of hotspots in termite genomes

Everitt,

Rönneburg,

Elsner

et al. 2024

Preprint

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Meiotic recombination is a fundamental evolutionary process that facilitates adaptation and the removal of deleterious genetic variation. Social Hymenoptera exhibit some of the highest recombination rates among metazoans, whereas high recombination rates have not been found among non-social species from this insect order. It is unknown whether elevated recombination rates are a ubiquitous feature of all social insects. In many metazoan taxa, recombination is mainly restricted to hotspots a few kilobases in length. However, little is known about the prevalence of recombination hotspots in insect genomes. Here we infer recombination rate and its fine-scale variation across the genomes of two social species from the insect order Blattodea: the termitesCryptotermes secundusandMacrotermes bellicosus. We used linkage-disequilibrium-based methods to infer recombination rate. We infer that recombination rates are less than 1 cM/Mb in both species, which is lower than the average metazoan rate. We also observed a highly punctate distribution of recombination in both termite genomes, indicative of the presence of recombination hotspots. We infer the presence of full-length PRDM9 genes in the genomes of both species. We also find that recombination rates in genes are correlated with inferred levels of germline DNA methylation. The finding of low recombination rates in termites indicates that eusociality is not universally connected to elevated recombination rate. We speculate that intense selection among haploid males promotes high recombination rates in social Hymenoptera. This study is one of the first to indicate the presence of PRDM9-based recombination hotspots in an insect genome.

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“…In termites, the XY sex determination system is thought to be widely conserved (Jankásek et al, 2021), where the sex ratio of eggs is expected to be 1:1 according to Mendel's law. However, some species show sex ratio bias, the cause of which remains unknown in many cases (Neoh and Lee, 2011).…”

Section: Introductionmentioning

confidence: 99%

Male’s influence on the primary sex ratio bias in Ryukyu drywood termite

et al. 2023

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Selfish genetic elements (SGEs) increase their transmission efficiency relative to the rest of the individual genome, which is often deleterious to individual fitness. Theoretical studies have suggested that intragenomic conflict over the sex ratio distortion between SGEs and the rest of the genome should lead to the evolution of sex-determining systems. However, in insects, there are relatively few studies other than those on Dipterans, which makes it difficult to understand the role of SGEs in the evolution of insect sex determination. This is partially due to the difficulties in observing SGEs under field conditions. The effect of SGEs is often masked by the counter-evolution of the resistance genes. Interpopulation cross-breeding experiments are effective to detect the SGEs and their resistance genes. If these populations have different SGEs and resistance genes, cross-breeding experiments reveal their existence by collapsing the evolutionary antagonistic state. The Ryukyu drywood termites Neotermes sugioi, distributed in the Ryukyu Islands, show male-biased sex ratios in pseudergates, nymphs, alates and soldiers both in Okinawa and Ishigaki Islands, but different degrees of bias have been reported between the islands. Male-specific microsatellite alleles have been reported in this species, which allowed us to identify the sex of the eggs and young larvae. In this study, we used the microsatellite locus with male-specific alleles to investigate the primary sex ratio of field colonies on Okinawa and Ishigaki islands and the sex ratio of offspring obtained through cross-breeding experiments between the islands. The primary sex ratios of field colonies were male-biased in Okinawa but not in Ishigaki. Cross-breeding experiments showed that Okinawa males tend to have a male-biased sex ratio in their offspring, but Ishigaki males do not. This result is consistent with the hypothesis that the male bias in this species is caused by SGEs, even though termites are phylogenetically distant from Diptera. Accumulation of knowledge on genetic conflicts in a wide range of taxa might be an important step toward elucidating the mechanisms of diversification of sex determination systems in insects.

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Blattodea Karyotype Database

Cited by 8 publications

References 70 publications

Genome size evaluations in cockroaches: new entries

Genome size evaluations in cockroaches: new entries

Unexpectedly low recombination rates and presence of hotspots in termite genomes

Male’s influence on the primary sex ratio bias in Ryukyu drywood termite

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