Systematics and phylogeny of the scorpion genus Brachistosternus Pocock 1893 (Arachnida, Scorpiones, Bothriuridae)

Se estudió la sistemática del género de escorpiones Brachistosternus; se redescribieron todas las especies conocidas del género y se describieron 19 nuevas entidades para la ciencia. Se brindan datos sobre distribución de todas las especies del género. Se realizó una clave para la mayor parte de las especies conocidas. Se realizó una filogenia del género utilizando caracteres morfológicos y moleculares, tanto por separado como de manera combinada. Los caracteres morfológicos corresponden a la pigmentación, a la ornamentación del metasoma y los pedipalpos, y en especial al patrón tricobotrial y a la morfología del hemiespermatóforo. Para los estudios moleculares se secuenciaron 5 genes, 2 nucleares: 18s y 28s pertenecientes al ADN ribosomal de la sub-unidad mayor, y 3 mitoncondriales: un fragmento bastante conservado de la subunidad I del gen para la Citocromo oxidasa c, y dos fragmentos bastante más lábiles de ADN mitocondrial, el fragmento 16S rDNA perteneciente al ADN ribosomal de la subunidad mayor, y el fragmento 12S rDNA perteneciente al ADN ribosomal de la subunidad menor, totalizando unos 4200 pares de bases. Los resultados de los análisis filogenéticos respaldan la monofilia del género; sin embargo, la división subgenérica actual no es soportada en todos los análisis realizados. En los análisis filogenéticos basados en caracteres morfológicos las especies del subgénero Brachistosternus aparecen anidadas dentro del subgénero Leptosternus, mientras que el subgénero Ministernus permanece como una entidad separada. En los análisis realizados sobre la base de caracteres moleculares, así como en los análisis basados en caracteres morfológicos y moleculares combinados, el subgénero Ministernus se conserva como un clado separado, mientras que las especies del subgénero Brachistosternus aparecen en la mayoría de los análisis, formando un clado con Br. roigalsinai, como grupo hermano del resto de las especies del subgénero Leptosternus. Sobre la base de estos resultados, se decide conservar solo dos subgéneros, Brachistosternus (= Leptosternus) y Ministernus. Se realizaron estudios citogenéticos de tres especies representativas de los distintos grupos obtenidos como resultado del análisis filogenético. Estas especies presentaron números haploides de n=23 y n=21, con cromosomas meta y submetacéntricos. Como resultado de esta contribución, el género Brachistosternus resulta ser el más diverso de Bothriuridae, y el segundo en diversidad en Sudamérica, con más de 40 especies descriptas.The systematics of the scorpion genus Brachistosternus has been studied; all known species of the genus have been redescribed, and 19 species are newly proposed. Data about the distribution of all species are provided. A key for most of the species of the genus is also provided. Phylogenetic analyses of the genus are performed using morphological and molecular data. Morphological characters correspond to pigmentation, external granulation and carinae, but mostly to the trichobothrial pattern and the morphology of the hemispermatophore. Five genes have been sequenced, 2 of them nuclear: 18S and 28S, belonging to major subunit of ribosomal DNA, and 3 mitochondrial genes: a fragment of cytochrome c oxidase, the fragment 16S rDNA belonging to major subunit of ribosomal DNA, and the fragment 12S rDNA belonging to minor subunit of ribosomal DNA; all these fragments involve about 4200 base pairs. The phylogenetic analysis supports the monophyly of the genus; however the present subgeneric division is not supported in all analyses. In the phylogenetic analysis performed using only morphological characters, the subgenus Leptosternus is nested within the subgenus Leptosternus, whereas the subgenus Ministernus remains as a separate clade. In the analysis performed using molecular characters, as well as in those using morphological and molecular characters together, the subgenus Ministernus always remains as a separate clade. On the other hand the species of subgenus Brachistosternus are, together with Br. roigalsinai, the sister group of the subgenus Leptosternus. Based on these results, it has been decided to keep only two subgenera, Brachistosternus (= Leptosternus) and Ministernus. Cytogentic analyses have also been performed on three representative species according to results of phylogenetic analysis. These species showed haploid numbers of n=21 and n=23, with meta and submetacentric chromosomes. As a result of this contribution, the genus Brachistosternus is the most diversified of Bothriuridae, and the second most diversified in South America, with more than 40 known speciesFil: Ojanguren Affilastro, Andrés Alejandro. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Sex-Linked Chromosome Heterozygosity in Males of Tityus confluens (Buthidae): A Clue about the Presence of Sex Chromosomes in Scorpions.

Scorpions of the genus Tityus show holokinetic chromosomes, achiasmatic male meiosis and an absence of heteromorphic sex chromosomes, like all Buthidae. In this work, we analysed the meiotic behaviour and chromosome rearrangements of a population of the scorpion Tityus confluens, characterising the cytotypes of males, females and embryos with different cytogenetic techniques. This revealed that all the females were structural homozygotes, while all the males were structural heterozygotes for different chromosome rearrangements. Four different cytotypes were described in males, which differed in chromosome number (2n = 5 and 2n = 6) and meiotic multivalent configurations (chains of four, five and six chromosomes). Based on a detailed mitotic and meiotic analysis, we propose a sequence of chromosome rearrangements that could give rise to each cytotype and in which fusions have played a major role. Based on the comparison of males, females and a brood of embryos, we also propose that the presence of multivalents in males and homologous pairs in females could be associated with the presence of cryptic sex chromosomes, with the male being the heterogametic sex. We propose that the ancestral karyotype of this species could have had homomorphic XY/XX (male/female) sex chromosomes and a fusion could have occurred between the Y chromosome and an autosome

A Fine-Scale Hotspot at the Edge: Epigean Arthropods from the Atacama Coast (Paposo-Taltal, Antofagasta Region, Chile)

The Atacama Desert at its margins harbors a unique biodiversity that is still very poorly known, especially in coastal fog oases spanning from Perú towards the Atacama coast. An outstand-ing species-rich fog oasis is the latitudinal fringe Paposo-Taltal, that is considered an iconic site of the Lomas formation. This contribution is the first to reveal the knowledge on arthropods of this emblematic coastal section. We used pitfall traps to study the taxonomic composition, richness, and abundance of terrestrial arthropods in 17 sample sites along a 100 km section of the coast between 24.5 and 25.5 southern latitude, in a variety of characteristic habitats. From a total of 9154 individuals, we were able to identify 173 arthropod species grouped into 118 genera and 57 families. The most diverse group were insects, with 146 species grouped in 97 genera and 43 families, while arachnids were represented by 27 species grouped into 21 genera and 14 families. Current conservation challenges on a global scale are driving the creation and evaluation of potential conservation sites in regions with few protected areas, such as the margins of the Atacama Desert. Better taxonomic, distributional, and population knowledge is urgently needed to perform concrete conservation actions in a biodiversity hotspot at a desert edge.Fil: Pizarro Araya, Jaime. Universidad de La Serena; ChileFil: Alfaro, Fermín M.. Universidad de La Serena; ChileFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Departamento de Invertebrados. Area de Entomologia; ArgentinaFil: Moreira Muñoz, Andrés Sergio. Pontificia Universidad Católica de Valparaíso; Chil

Diagram of the hypothetical offspring of the crosses between males and females of the studied population of <i>Tityus confluens</i>.

<p>Colours and sizes are in accordance with the diagram in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164427#pone.0164427.g005" target="_blank">Fig 5</a>; the proposed X and Y chromosomes are indicated. Only alternate segregation of multivalents was considered for the formation of male gametes.</p

FISH with 28S rDNA probes (a-c) and C-banding (d-f) of females and embryos of <i>Tityus confluens</i>.

<p>a, d. Female mitotic prometaphase (2n = 6); b, e. Embryonic mitotic prometaphase (2n = 6); c, f. Embryonic mitotic prometaphase (2n = 5). White arrowheads indicate 28S rDNA hybridisation signals. White arrows indicate C-bands corresponding to rDNA sites. Scale bar = 10 μm</p

C-banding of mitotic prometaphase (a-d) and postpachytene (e-h) cells of males of <i>Tityus confluens</i>.

<p>Cytotype A: a. 2n = 6; e. II+IV. Cytotype B: b. 2n = 5; f. V version 1. Cytotype C: c. 2n = 5; g. V version 2. Cytotype D: d, 2n = 6; h. VI. White arrows indicate C-bands corresponding to rDNA sites. Scale bar = 10μm.</p

Diagram of the chromosome rearrangements that could give rise to each cytotype.

<p>a. Hypothetical ancestral karyotype and possible rearrangements that gave rise to cytotype A; b. Cytotype A and possible rearrangements that gave rise to the three other cytotypes; c. Cytotype B; d. Cytotype C; e. Cytotype D. Colours indicate the four different chromosome pairs of the hypothetical ancestral karyotype. Idiograms of cytotype A-D are in accordance with relative lengths shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164427#pone.0164427.t001" target="_blank">Table 1</a>. Letters inside the chromosomes indicate terminal regions. Schematic representations of cells in b, c, d and e correspond to those shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164427#pone.0164427.g002" target="_blank">Fig 2c, 2f, 2i and 2l</a>, respectively.</p

Chromosome measurements of males, females and embryos of <i>Tityus confluens</i>.

<p>Relative lengths expressed as percentage of total diploid complement length (%TCL). Mean values and standard deviations (SD) are given. Measurements are ordered by decreasing length and do not necessary imply homology between different cytotypes.</p

Giemsa staining of mitosis and meiosis of males of <i>Tityus confluens</i>.

<p>Cytotype A (a-d): a. Mitotic metaphase (2n = 6); b. Postpachytene (II+IV); c, d. Metaphases II (n = 3). Cytotype B (e-h): e. Mitotic prometaphase (2n = 5); f. Postpachytene (V, version 1); g, h. Metaphases II (n = 3, n = 2). Cytotype C (i-l): i. Mitotic prometaphase (2n = 5); j. Postpachytene (V, version 2); k, l. Metaphases II (n = 3, n = 2). Cytotype D (m-q): m. Mitotic prometaphase (2n = 6); n. Postpachytene (VI, chain form); o. Postpachytene (VI, ring-bearing form) p, q. Metaphases II (n = 3). Scale bar = 10μm.</p

Silver staining (a, d, g, j), FISH with 28S rDNA (b, c, e, f, h, i, k, l) and (TTAGG)_<i>n</i> telomeric probes (m, n, o) in males of <i>Tityus confluens</i>.

<p>Cytotype A: a, b. Mitotic prometaphase (2n = 6); c, m. Postpachytene (II+IV). Cytotype B: d, e. Mitotic prometaphase (2n = 5); f, n. Postpachytene (V, version 1); Cytotype C: g, h. Mitotic prometaphase (2n = 5); i, o. Postpachytene (V, version 2). Cytotype D: j. Mitotic prometaphase (2n = 6); k. Early mitotic anaphase (2n = 6); l. Postpachytene (VI). Black arrowheads indicate Ag-NORs. White arrowheads indicate 28S rDNA hybridisation signals. Scale bar = 10 μm.</p