Classical and molecular cytogenetics of the scorpions of family Buthidae Koch 1837 from Argentina

En este trabajo de Tesis se estudiaron mediante citogenética clásica ymolecular las nueve especies de escorpiones de la familia Buthidae descriptas parala Argentina, además de una especie aún no descripta. Se analizó el cariotipo, eldesarrollo meiótico, la distribución de la heterocromatina constitutiva y lalocalización de las regiones organizadoras nucleolares y de repeticionesteloméricas. Todas las especies presentaron cromosomas holocinéticos y meiosisaquiasmática en machos, como es característico de la familia. Se observó una granvariación inter- e intraespecífica para el número diploide y las configuracionesmeióticas en machos: Ananteris balzanii, 2n=14 (4II+VI); Tityus (Tityus) bahiensis, 2n=12 (2II+III configuración 2 + V), 2n=13 (4II+V, 3II+VII configuración 1, 3II+VIIconfiguración 2), 2n=14 (4II+VI) y 2n=15 (6II+III configuración 1); Tityus (Tityus)confluens, 2n=5 (V configuración 1, V configuración 2) y 2n=6 (II+IV, VI); Tityus (Tityus) argentinus, 2n=9 (II+VII) y 2n=10 (5II, 3II+IV, X); Tityus (Tityus) sp. 1, 2n=32 (16II) y 2n=31 (14II+III); Tityus (Tityus) uruguayensis, 2n=31 (12II+VII, 10II+IV configuración 1+VII, 10II+IV configuración 2 +VII); Tityus (Archaeotityus)paraguayensis, 2n=16 (8II, 5II+2III, 6II+IV); Zabius birabeni, 2n=16 y Zabius fuscus, 2n=18 (9II, 7II+IV). Los multivalentes en meiosis I, producto de rearregloscromosómicos, se encontraron en estado polimórfico en T. confluens, T.paraguayensis, Tityus sp. 1 y T. uruguayensis, y en estado polimórfico y politípicoen T. bahiensis, T. argentinus y Z. fuscus. La segregación cromosómica en meiosis I fue balanceada, tanto en individuos homocigotas como heterocigotasestructurales. Las hembras partenogenéticas de distintas poblaciones de Tityus (Tityus)trivittatus presentaron 2n=6, sin variabilidad cariotípica. En la meiosis femenina en Z. fuscus se describió un estadio difuso y bivalentes en forma de anillo en profase I tardía; se discute el posible origen de estos bivalentes en el marco de una meiosisquiasmática o aquiasmática. La localización de la heterocromatina constitutiva mostró variaciones entrelas especies. La mayoría presentó bloques terminales en todos los cromosomas eintersticiales en algunos, mientras que A. balzanii, T. paraguayensis y Z. fuscuspresentaron bloques terminales en pocos pares cromosómicos. Las regionesorganizadoras nucleolares se localizaron principalmente en un par cromosómico enposición terminal y asociadas a un bloque conspicuo de heterocromatinaconstitutiva; las excepciones fueron dos pares cromosómicos con NORs terminalesen T. uruguayensis y la posición subterminal en A. balzanii. Las repeticionesteloméricas (TTAGG)n se localizaron exclusivamente en regiones terminales ypermitieron el análisis detallado de la profase meiótica de machos y hembras. Los estudios poblacionales de T. confluens, T. bahiensis y T. argentinuspermitieron proponer qué cromosomas estaban implicados en los rearregloscromosómicos que originan los multivalentes, así como en las variaciones de losnúmeros diploides. La variabilidad cromosómica intraespecífica se debeprincipalmente a fusiones y, en menor grado, a translocaciones recíprocas. Losestudios citogenéticos pueden aportar datos para la delimitación y diagnosis denuevas especies, como en T. uruguayensis y Tityus sp. 1. El estudio de una población de T. confluens permitió proponer que existiríancromosomas sexuales crípticos homomórficos XY/XX (macho/hembra), que enalgunas especies se asociarían con la heterocigosis estructural en machos y lahomocigosis estructural en hembras.In this Thesis the nine species of Buthidae scorpions described for Argentinaand one undescribed species were cytogenetically analyzed by classical andmolecular techniques. Karyotype, meiotic division, constitutive heterochromatindistribution and the localization of nucleolar organizer regions and telomeric repeatswere analyzed. All the species presented holokinetic chromosomes andachiasmatic male meiosis, as is characteristic of this family. A great intra- andinterspecific variation of chromosome number and meiotic configurations wasobserved in males: Ananteris balzanii, 2n=14 (4II+VI); Tityus (Tityus) bahiensis, 2n=12 (2II+III configuration 2 + V), 2n=13 (4II+V, 3II+VII configuration 1, 3II+VIIconfiguration 2), 2n=14 (4II+VI) and 2n=15 (6II+III configuration 1); Tityus (Tityus)confluens, 2n=5 (V configuration 1, V configuration 2) and 2n=6 (II+IV, VI); Tityus (Tityus) argentinus, 2n=9 (II+VII) and 2n=10 (5II, 3II+IV, X); Tityus (Tityus) sp. 1, 2n=32 (16II) and 2n=31 (14II+III); Tityus (Tityus) uruguayensis, 2n=31 (12II+VII, 10II+IV configuration 1+VII, 10II+IV configuration 2 +VII); Tityus (Archaeotityus)paraguayensis, 2n=16 (8II, 5II+2III, 6II+IV); Zabius birabeni, 2n=16 and Zabiusfuscus, 2n=18 (9II, 7II+IV). Multivalent associations at meiosis I, as a consequenceof chromosomal rearrangements, were polymorhpic in T. confluens, T.paraguayensis, Tityus sp. 1 and T. uruguayensis, and polymorphic and polytypic in T. bahiensis, T. argentinus and Z. fuscus. Chromosome segregation was regular atmeiosis I, both in structural homozygotes and heterozygotes. Parthenogenetic females of Tityus (Tityus) trivittatus from differentpopulations presented 2n=6 and showed no karyotypic variability. Female meiosisof Z. fuscus revealed a diffuse stage and the presence of ring-shaped bivalents atlate prophase I; the possible origin of these bivalents in the framework of chiasmaticor achiasmatic female meiosis is discussed. Constitutive heterochromatin distribution was variable between the species. Most of the species presented heterochromatin at terminal regions of allchromosomes and at interstitial regions of some chromosomes, while A. balzanii, T.paraguayensis and Z. fuscus presented only terminal heterochromatin in a fewchromosome pairs. Nucleolar organizer regions were mainly found at the terminalheterochromatic region of one chromosome pair; the exceptions were the presenceof two NOR pairs in T. uruguayensis and the subterminal localization in A. balzanii. Telomeric (TTAGG)n repeats were found only at terminal regions and permitted adetailed analysis of male and female meiotic prophase. Population studies of T. confluens, T. bahiensis and T. argentinus allowed topropose the chromosomes involved in the rearrangements and in the variations ofdiploid numbers. Intraspecific chromosome variability is originated by fusions and, ina lesser extent, by reciprocal translocations. Cytogenetic studies may provide datafor the delimitation and diagnosis of new species, as is the case of T. uruguayensisand Tityus sp. 1. The study of a population of T. confluens allowed to propose the presence ofhomomorphic cryptic sex chromosomes XY/XX (male/female), which in somespecies would be associated with structural heterozygosity in males and structuralhomozygosity in females.Fil: Adilardi, Renzo Sebastián. 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.Fil: Adilardi, Renzo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Citogenética y Evolución; ArgentinaFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; ArgentinaFil: Mola, Liliana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Citogenética y Evolución; Argentin

Cytogenetic analysis on geographically distant parthenogenetic populations of Tityus trivittatus Kraepelin, 1898 (Scorpiones, Buthidae): karyotype, constitutive heterochromatin and rDNA localization

Tityus trivittatus Kraepelin, 1898 is the most medically important scorpion species of Argentina, and parthenogenetic populations are present in the major cities of this country. We performed a detailed cytogenetic analysis of specimens of three synanthropic parthenogenetic populations, all distant about 900 km from each other, using Ag-NOR, C-banding, DAPI/CMA3 staining and FISH with autologous 28S rDNA probes. The karyotype of females and embryos from the three populations showed 2n=6, with two large and four middle-sized holokinetic chromosomes. Constitutive heterochromatin was found in terminal and interstitial location and its pattern allowed the identification of three chromosome pairs. NORs were found on the terminal heterochromatic region of one pair of middle-sized chromosomes. The use of fluorochromes to characterize heterochromatin showed the absence of GC-rich heterochromatin and a low and variable number of AT-rich heterochromatic regions. We propose that a possible explanation for the lack of karyotypic variation between these geographically distant populations could be a recent colonization of urban areas by human means of synanthropic specimens from a single lineage of northeastern Argentina.Fil: Adilardi, Renzo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Pque. Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia". Departamento de Invertebrados. Area de Entomologia; ArgentinaFil: Marti, Dardo Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Mola, Liliana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Classical and molecular cytogenetics of the scorpions of family Buthidae Koch 1837 from Argentina

En este trabajo de Tesis se estudiaron mediante citogenética clásica ymolecular las nueve especies de escorpiones de la familia Buthidae descriptas parala Argentina, además de una especie aún no descripta. Se analizó el cariotipo, eldesarrollo meiótico, la distribución de la heterocromatina constitutiva y lalocalización de las regiones organizadoras nucleolares y de repeticionesteloméricas. Todas las especies presentaron cromosomas holocinéticos y meiosisaquiasmática en machos, como es característico de la familia. Se observó una granvariación inter- e intraespecífica para el número diploide y las configuracionesmeióticas en machos: Ananteris balzanii, 2n=14 (4II+VI); Tityus (Tityus) bahiensis, 2n=12 (2II+III configuración 2 + V), 2n=13 (4II+V, 3II+VII configuración 1, 3II+VIIconfiguración 2), 2n=14 (4II+VI) y 2n=15 (6II+III configuración 1); Tityus (Tityus)confluens, 2n=5 (V configuración 1, V configuración 2) y 2n=6 (II+IV, VI); Tityus (Tityus) argentinus, 2n=9 (II+VII) y 2n=10 (5II, 3II+IV, X); Tityus (Tityus) sp. 1, 2n=32 (16II) y 2n=31 (14II+III); Tityus (Tityus) uruguayensis, 2n=31 (12II+VII, 10II+IV configuración 1+VII, 10II+IV configuración 2 +VII); Tityus (Archaeotityus)paraguayensis, 2n=16 (8II, 5II+2III, 6II+IV); Zabius birabeni, 2n=16 y Zabius fuscus, 2n=18 (9II, 7II+IV). Los multivalentes en meiosis I, producto de rearregloscromosómicos, se encontraron en estado polimórfico en T. confluens, T.paraguayensis, Tityus sp. 1 y T. uruguayensis, y en estado polimórfico y politípicoen T. bahiensis, T. argentinus y Z. fuscus. La segregación cromosómica en meiosis I fue balanceada, tanto en individuos homocigotas como heterocigotasestructurales. Las hembras partenogenéticas de distintas poblaciones de Tityus (Tityus)trivittatus presentaron 2n=6, sin variabilidad cariotípica. En la meiosis femenina en Z. fuscus se describió un estadio difuso y bivalentes en forma de anillo en profase I tardía; se discute el posible origen de estos bivalentes en el marco de una meiosisquiasmática o aquiasmática. La localización de la heterocromatina constitutiva mostró variaciones entrelas especies. La mayoría presentó bloques terminales en todos los cromosomas eintersticiales en algunos, mientras que A. balzanii, T. paraguayensis y Z. fuscuspresentaron bloques terminales en pocos pares cromosómicos. Las regionesorganizadoras nucleolares se localizaron principalmente en un par cromosómico enposición terminal y asociadas a un bloque conspicuo de heterocromatinaconstitutiva; las excepciones fueron dos pares cromosómicos con NORs terminalesen T. uruguayensis y la posición subterminal en A. balzanii. Las repeticionesteloméricas (TTAGG)n se localizaron exclusivamente en regiones terminales ypermitieron el análisis detallado de la profase meiótica de machos y hembras. Los estudios poblacionales de T. confluens, T. bahiensis y T. argentinuspermitieron proponer qué cromosomas estaban implicados en los rearregloscromosómicos que originan los multivalentes, así como en las variaciones de losnúmeros diploides. La variabilidad cromosómica intraespecífica se debeprincipalmente a fusiones y, en menor grado, a translocaciones recíprocas. Losestudios citogenéticos pueden aportar datos para la delimitación y diagnosis denuevas especies, como en T. uruguayensis y Tityus sp. 1. El estudio de una población de T. confluens permitió proponer que existiríancromosomas sexuales crípticos homomórficos XY/XX (macho/hembra), que enalgunas especies se asociarían con la heterocigosis estructural en machos y lahomocigosis estructural en hembras.In this Thesis the nine species of Buthidae scorpions described for Argentinaand one undescribed species were cytogenetically analyzed by classical andmolecular techniques. Karyotype, meiotic division, constitutive heterochromatindistribution and the localization of nucleolar organizer regions and telomeric repeatswere analyzed. All the species presented holokinetic chromosomes andachiasmatic male meiosis, as is characteristic of this family. A great intra- andinterspecific variation of chromosome number and meiotic configurations wasobserved in males: Ananteris balzanii, 2n=14 (4II+VI); Tityus (Tityus) bahiensis, 2n=12 (2II+III configuration 2 + V), 2n=13 (4II+V, 3II+VII configuration 1, 3II+VIIconfiguration 2), 2n=14 (4II+VI) and 2n=15 (6II+III configuration 1); Tityus (Tityus)confluens, 2n=5 (V configuration 1, V configuration 2) and 2n=6 (II+IV, VI); Tityus (Tityus) argentinus, 2n=9 (II+VII) and 2n=10 (5II, 3II+IV, X); Tityus (Tityus) sp. 1, 2n=32 (16II) and 2n=31 (14II+III); Tityus (Tityus) uruguayensis, 2n=31 (12II+VII, 10II+IV configuration 1+VII, 10II+IV configuration 2 +VII); Tityus (Archaeotityus)paraguayensis, 2n=16 (8II, 5II+2III, 6II+IV); Zabius birabeni, 2n=16 and Zabiusfuscus, 2n=18 (9II, 7II+IV). Multivalent associations at meiosis I, as a consequenceof chromosomal rearrangements, were polymorhpic in T. confluens, T.paraguayensis, Tityus sp. 1 and T. uruguayensis, and polymorphic and polytypic in T. bahiensis, T. argentinus and Z. fuscus. Chromosome segregation was regular atmeiosis I, both in structural homozygotes and heterozygotes. Parthenogenetic females of Tityus (Tityus) trivittatus from differentpopulations presented 2n=6 and showed no karyotypic variability. Female meiosisof Z. fuscus revealed a diffuse stage and the presence of ring-shaped bivalents atlate prophase I; the possible origin of these bivalents in the framework of chiasmaticor achiasmatic female meiosis is discussed. Constitutive heterochromatin distribution was variable between the species. Most of the species presented heterochromatin at terminal regions of allchromosomes and at interstitial regions of some chromosomes, while A. balzanii, T.paraguayensis and Z. fuscus presented only terminal heterochromatin in a fewchromosome pairs. Nucleolar organizer regions were mainly found at the terminalheterochromatic region of one chromosome pair; the exceptions were the presenceof two NOR pairs in T. uruguayensis and the subterminal localization in A. balzanii. Telomeric (TTAGG)n repeats were found only at terminal regions and permitted adetailed analysis of male and female meiotic prophase. Population studies of T. confluens, T. bahiensis and T. argentinus allowed topropose the chromosomes involved in the rearrangements and in the variations ofdiploid numbers. Intraspecific chromosome variability is originated by fusions and, ina lesser extent, by reciprocal translocations. Cytogenetic studies may provide datafor the delimitation and diagnosis of new species, as is the case of T. uruguayensisand Tityus sp. 1. The study of a population of T. confluens allowed to propose the presence ofhomomorphic cryptic sex chromosomes XY/XX (male/female), which in somespecies would be associated with structural heterozygosity in males and structuralhomozygosity in females.Fil: Adilardi, Renzo Sebastián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Robust, versatile DNA FISH probes for chromosome-specific repeats in <i>Caenorhabditis elegans</i> and <i>Pristionchus pacificus</i>

AbstractRepetitive DNA sequences are useful targets for chromosomal fluorescence in situ hybridization. We analyzed recent genome assemblies of Caenorhabditis elegansPristionchus pacificu

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

Chromosome puzzle in the southernmost populations of the medically important scorpion Tityus bahiensis (Perty 1833) (Buthidae), a polymorphic species with striking structural rearrangements

The scorpion Tityus bahiensis is the most common scorpion species of medical importance with sexual reproduction in South America. Many of the populations cytogenetically studied so far are polymorphic both for chromosome number and meiotic configuration in males. In this work, we perform cytogenetic analysis of three of the most meridional populations of T. bahiensis occurring in north-eastern Argentina (Misiones province), which showed numerical and structural variations with respect to previously studied populations. We describe four new diploid numbers in males for this species, from 2n = 12 to 2n = 15, seven different cytotypes, and we analyze the chromosome rearrangements involved in the different multivalent associations observed during meiosis (II, III, V, VI, VII and IX). Ribosomal DNA is invariably present at one terminal region on each of two chromosomes. Blocks of constitutive heterochromatin of different sizes are found at the terminal regions of every chromosome in the different cytotypes, along with subterminal and interstitial blocks in some chromosomes. Based on the rDNA and constitutive heterochromatin localization, we analyzed chromosome evolution within these populations. We propose that all the cytotypes could have originated from a hypothetical ancestral karyotype with 2n = 18 and 9 bivalents at meiosis I but followed two pathways with different sequences of mainly fusions and some translocations from the ancestral karyotype. Furthermore, we review all the cytogenetically studied populations of this species and their distribution to discuss the chromosomal evolution of this polymorphic species.Fil: Adilardi, Renzo Sebastián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Citogenética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Marti, Dardo Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Mola, Liliana Maria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Citogenética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

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

Male and female meiosis in the mountain scorpion Zabius fuscus (Scorpiones, Buthidae): Heterochromatin, rDNA and TTAGG telomeric repeats

All cytogenetically studied scorpions present male achiasmatic meiosis and lack heteromorphic sex chromosomes. In contrast, information about female meiosis in scorpions is scarce due to the difficulty of finding meiotic cells. The genus Zabius includes three described species and no chromosome studies have been performed on it until now. We analyzed the constitutive heterochromatin distribution, NORs and telomeric sequences in mitosis and meiosis of males and females of different populations of Zabius fuscus. All specimens presented 2n=18 holokinetic chromosomes that gradually decreased in size. Male meiosis presented nine bivalents and a polymorphism for one reciprocal translocation in one population. Telomeric signals were detected at every terminal region, confirming also the presence of a (TTAGG)n motif in Buthidae. Constitutive heterochromatin was found in three chromosome pairs at a terminal region; moreover, NORs were embedded in the heterochromatic region of the largest pair. Chromosome size and landmarks allowed us to propose the chromosomes involved in the rearrangement. In four females, cells at different prophase I stages were analyzed. We describe a diffuse stage and the presence of ring-shaped bivalents. We discuss the possible origin of these bivalents in the framework of chiasmatic or achiasmatic female meiosis. These results contribute to increase the scarce evidence of female meiosis in scorpions and raise new questions about its mechanism.Fil: Adilardi, Renzo Sebastián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; ArgentinaFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Mattoni, Camilo Ivan. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Mola, Liliana Maria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentin

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