Elio R. Castillo

Tracking the evolution of sex chromosome systems in Melanoplinae grasshoppers through chromosomal mapping of repetitive DNA sequences

BackgroundThe accumulation of repetitive DNA during sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the evolution of sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the evolution of sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀ sex chromosome systems.ResultsOur data indicate a non-spreading of heterochromatic blocks and pool of repetitive DNAs (C0t-1 DNA) in the sex chromosomes; however, the spreading of multigene families among the neo-sex chromosomes of Eurotettix and Dichromatos was remarkable, particularly for 5S rDNA. In autosomes, FISH mapping of multigene families revealed distinct patterns of chromosomal organization at the intra- and intergenomic levels.ConclusionsThese results suggest a common origin and subsequent differential accumulation of repetitive DNAs in the sex chromosomes of Dichromatos and an independent origin of the sex chromosomes of the neo-XY and neo-X1X2Y systems. Our data indicate a possible role for repetitive DNAs in the diversification of sex chromosome systems in grasshoppers.

Neo-sex chromosome diversity in Neotropical melanopline grasshoppers (Melanoplinae, Acrididae).

We report the results of a study on the neo-sex chromosome systems of six Neotropical Melanoplinae species for contributing to a better understanding of their origin and behaviour of these systems. Our analyses included detailed descriptions of the structure and behaviour of the sex chromosome configurations in male and female meiosis of species belonging to the genera Ronderosia, Dichromatos and Atrachelacris. Three species, R. forcipatus, R. malloi and A. unicolor, showed typical Robertsonian fusion-derived neo sex-chromosomes. However, the male metaphase I orientation of R. bergi sex pair indicated that more than one rearrangement was involved in its origin. The two species of Dichromatos presented a multiple neo-X1X2Y/X1X1X2X2 sex system, with two Robertsonian fusions involved in their genesis. Observations of female meiosis, confirmed the nature of the sex-chromosomes analyzed. Our results also showed different degrees of homology divergence between the neo-sex chromosomes and emphasize the plasticity of the chromosome complement of the Neotropical Melanoplinae to establish Robertsonian fusions and generate novel sex-chromosome systems. We also discuss karyotypic diversity within this group in terms of the centromeric drive theory of chromosomal evolution.

Effects of Abiotic Factors on the Geographic Distribution of Body Size Variation and Chromosomal Polymorphisms in Two Neotropical Grasshopper Species (Dichroplus: Melanoplinae: Acrididae)

We review the effects of abiotic factors on body size in two grasshopper species with large geographical distributions: Dichroplus pratensis and D. vittatus, inhabiting Argentina in diverse natural habitats. Geographical spans for both species provide an opportunity to study the effects of changes in abiotic factors on body size. The analyses of body size distribution in both species revealed a converse Bergmannian pattern: body size is positively correlated with latitude, altitude, and seasonality that influences time available for development and growth. Allen’s rule is also inverted. Morphological variability increases towards the ends of the Bergmannian clines and, in D. pratensis, is related with a central-marginal distribution of chromosomal variants that influence recombination. The converse Bergmannian patterns influence sexual size dimorphism in both species but in different fashions. Body size variation at a microspatial scale in D. pratensis is extremely sensitive to microclimatic clines. We finally compare our results with those for other Orthopteran species.

Revision of the family Carabodidae (Acari: Oribatida) V (third part). Redefinition of Congocepheus, definition of Cavaecarabodes gen. nov., and descriptions of three new species, Congocepheus germani sp. nov., Cavaecarabodes pulchritude gen. nov., sp. nov., and Cavaecarabodes anouchkae gen. nov., sp. nov.

Redefinition of Congocepheus Balogh, 1958 and description of Congocepheus germani sp. nov., that displays notogastral neotrichy, which was previously unknown in the genus. Definition of Cavaecarabodes gen. nov. together with the descriptions of Cavaecarabodes pulchritude sp. nov. (type) from Gabon and Cavaecarabodes anouchkae sp. nov. from Madagascar has been provided. http://zoobank.org/urn:lsid:zoobank.org:pub:97F8E1B8-5526-44EC-BFFC-59554D4C575D

Inexorable spread: inexorable death? The fate of neo-XY chromosomes of grasshoppers

2008;Pannell and Pujol 2009), but it does not take into account theevolutionary fate of the neo-chromosomes. We discuss herethat, although neo-XY chromosomes of grasshoppers maybe a useful model to explain the spread of a new chromo-somal rearrangement, they are not a predictive example ofsex-chromosome evolution and recycling.The origin of sex-chromosomes, and the mechanismsthrough which they influence sex-determination, are biolog-ical issues of the utmost relevance for the understandingof a number of evolutionary problems that have been withus since the earliest times of Mendelism and the chromo-some theory of heredity (Kingsland 2007; Bidau and Marti2001; Castillo

Oribatid mites from deep soils of Hòn Chông limestone hills, Vietnam: the family Lohmanniidae (Acari: Oribatida), with the descriptions of Bedoslohmannia anneae n. gen., n. sp., and Paulianacarus vietnamese n. sp.

ABSTRACT In this first work on the oribatid mite fauna of Hòn Chông limestone hills, Vietnam, we describe Bedoslohmannia anneae n. gen., n. sp. and Paulianacarus Vietnamese n. sp., in both cases studied with optical microscopy. Bedoslohmannia n. gen. presents a very interesting “leg-folding process”, unusually shaped legs and significant notogastral neotrichy. Paulianacarus Balogh, 1960 is newly reported from Vietnam and P. Vietnamese n. sp. is most similar to P. rugulosus Mahunka, 1995 from Thailand.

Phylogeny and chromosomal diversification in the Dichroplus elongatus species group (Orthoptera, Melanoplinae)

In an attempt to track the chromosomal differentiation in the Dichroplus elongatus species group, we analyzed the karyotypes of four species with classical cytogenetic and mapping several multigene families through fluorescent in situ hybridization (FISH). We improved the taxon sampling of the D. elongatus species group adding new molecular data to infer the phylogeny of the genus and reconstruct the karyotype evolution. Our molecular analyses recovered a fully resolved tree with no evidence for the monophyly of Dichroplus. However, we recovered several stable clades within the genus, including the D. elongatus species group, under the different strategies of tree analyses (Maximum Parsimony and Maximum Likelihood). The chromosomal data revealed minor variation in the D. elongatus species group’s karyotypes caused by chromosome rearrangements compared to the phylogenetically related D. maculipennis species group. The karyotypes of D. intermedius and D. exilis described herein showed the standard characteristics found in most Dichroplini, 2n = 23/24, X0♂ XX♀, Fundamental number (FN) = 23/24. However, we noticed two established pericentric inversions in D. intermedius karyotype, raising the FN to 27♂/28♀. A strong variation in the heterochromatic blocks distribution was evidenced at interespecific level. The multigene families’ mapping revealed significant variation, mainly in rDNA clusters. These variations are probably caused by micro chromosomal changes, such as movement of transposable elements (TEs) and ectopic recombination. These observations suggest a high genomic dynamism for these repetitive DNA sequences in related species. The reconstruction of the chromosome character “variation in the FN” posits the FN = 23/24 as the ancestral state, and it is hypothesized that variations due to pericentric inversions has arisen independently three times in the evolutionary history of Dichroplus. One of these independent events occurred in the D. elongatus species group, where D. intermedius is the unique case with the highest FN described in the tribe Dichroplini.

Neo-sex Chromosomes in the Maculipennis Species Group (Dichroplus: Acrididae, Melanoplinae): The Cases of D. maculipennis and D. vittigerum

South American melanopline grasshoppers display a disproportionate number of derived karyotypes, including many cases of neo-sex chromosome systems. This is especially true of the genus Dichroplus and its Maculipennis species group. We analyzed the karyotype and neo-sex chromosomes in mitosis and meiosis of Dichroplus maculipennis and D. vittigerum from Argentina using conventional and fluorescent cytogenetic protocols in order to elucidate the behavior and origin of these neo-XY systems in relation to the current phylogeny of this group. Our results showed that D. maculipennis (2n = 22♂/22♀; neoXY/neoXX) and D. vittigerum, whose karyotype is described here for the first time (2n = 18♂/18♀; neoXY/neoXX), show highly evolved neo-XY systems, although with significant differences between them. Furthermore, both species differ for two autosomal fixed Robertsonian fusions present in D. vittigerum. Analysis of karyotypic character state optimization strongly suggests the independent origin and evolution of neo-sex systems within this species group.

Revision of the family Carabodidae (Acari, Oribatida) VII. Redefinition of the genus Malgasodes; redescription of M. curvisetus Mahunka, 2000; and complementary description of M. hungarorum Mahunka, 2010. Phylogenetic relationships between Malgasodes, Bovicarabodes, Afticarabodes, Congocepheus and Cavaecarabodes are discussed

Abstract The genus Malgasodes is redefined; the type species M. curvisetus Mahunka, 2000, is redescribed by means of studies using optic and Scanning Electron Microsopy (SEM), and a complementary description of M. hungarorum Mahunka, 2000 is included. Comparison of genera Malgasodes Mahunka, 2000, Bovicarabodes Fernandez, Theron, Rollard, 2013a, Cavaecarabodes Fernandez, Theron, Rollard, Rodriguez Castillo, 2014, Afticarabodes Fernandez, Theron, Rollard, 2013b, and Congocepheus Balogh, 1958 is made. Problems concerning chaetotaxy, regressive evolution and neotrichy are explained and phylogenetic relationships between Malgasodes, Bovicarabodes, Afticarabodes, Congocepheus and Cavaecarabodes are discussed.

Uncovering the evolutionary history of neo-XY sex chromosomes in the grasshopper Ronderosia bergii (Orthoptera, Melanoplinae) through satellite DNA analysis

BackgroundNeo-sex chromosome systems arose independently multiple times in evolution, presenting the remarkable characteristic of repetitive DNAs accumulation. Among grasshoppers, occurrence of neo-XY was repeatedly noticed in Melanoplinae. Here we analyzed the most abundant tandem repeats of R. bergii (2n = 22, neo-XY♂) using deep Illumina sequencing and graph-based clustering in order to address the neo-sex chromosomes evolution.ResultsThe analyses revealed ten families of satDNAs comprising about ~1% of the male genome, which occupied mainly C-positive regions of autosomes. Regarding the sex chromosomes, satDNAs were recorded within centromeric or interstitial regions of the neo-X chromosome and four satDNAs occurred in the neo-Y, two of them being exclusive (Rber248 and Rber299). Using a combination of probes we uncovered five well-defined cytological variants for neo-Y, originated by multiple paracentric inversions and satDNA amplification, besides fragmented neo-Y. These neo-Y variants were distinct in frequency between embryos and adult males.ConclusionsThe genomic data together with cytogenetic mapping enabled us to better understand the neo-sex chromosome dynamics in grasshoppers, reinforcing differentiation of neo-X and neo-Y and revealing the occurrence of multiple additional rearrangements involved in the neo-Y evolution of R. bergii. We discussed the possible causes that led to differences in frequency for the neo-Y variants between embryos and adults. Finally we hypothesize about the role of DNA satellites in R. bergii as well as putative historical events involved in the evolution of the R. bergii neo-XY.