Navegando por Palavras-chave "nucleolar organizer region"
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- ItemSomente MetadadadosChromosome mapping of 28S ribosomal genes in 11 species of Cassidinae (Coleoptera: Chrysomelidae)(Czech Acad Sci, Inst Entomology, 2017) Lopes, Amalia T.; Fernandes, Flavia R.; Schneider, Marielle C. [UNIFESP]In this study, we examined for the first time the distribution of the 28S ribosomal genes in beetles of the subfamily Cassidinae. More than 55% of the species in this subfamily have a similar karyotype, 2n = 16 + Xy(p). For this work, we selected species belonging to the tribes Cassidini and Mesomphaliini, which have, respectively, the most conserved and diversified karyotype characteristics within the Cassidinae. An analysis of 11 species revealed that rDNA sites on one pair of autosomes is the most frequent pattern, occurring in 10 species. This condition occurs in the seven genera examined and in species of both of the tribes, Cassidini and Mesomphaliini. Nevertheless, the differences in the locations of 28S rDNA were more pronounced in the tribe Cassidini and among species with similar karyotype characteristics. On the other hand, in Mesomphaliini, the increase in the diploid number was not accompanied by an increase in the number of ribosomal sites. Moreover, the comparison of the number and localization of major rDNA sites with the distribution of constitutive heterochromatin indicates that there is no direct correlation between the dispersion of constitutive heterochromatin and 28S rDNA genes in Cassidinae.
- ItemAcesso aberto (Open Access)Chromosomes of Theridiidae spiders (Entelegynae): interspecific karyotype diversity in Argyrodes and diploid number intraspecific variability in Nesticodes rufipes(Sociedade Brasileira de Genética, 2010-01-01) Stavale, Leila Miguel; Schneider, Marielle Cristina [UNIFESP]; Araujo, Douglas; Brescovit, Antonio Domingos; Cella, Doralice Maria; Universidade Estadual Paulista (UNESP); Universidade Federal de São Paulo (UNIFESP); Universidade Estadual de Mato Grosso do Su; Instituto Butantan Laboratório de ArtrópodesTheridiidae is a derived family within the Araneoidea clade. In contrast to closely related groups, the 2n(male) = 20+X1X2 with acro/telocentric chromosomes is the most widespread karyotype among the theridiid spiders. In this work, the cytogenetic analysis of Argyrodes elevatus revealed original chromosome features different from those previously registered for Theridiidae, including the presence of 2n(male) = 20+X with meta/submetacentric chromosomes. Most individuals of Nesticodes rufipes showed family conserved karyotype characteristics. However, one individual had a 2n(male) = 24 due to the presence of an extra chromosome pair, which exhibited regular behavior and reductional segregation during meiosis. After silver staining, mitotic cells exhibited NORs localized on the terminal regions of the short arms of pairs 2, 3, and 4 of A. elevatus and on the terminal regions of long arms of pair 4 of N. rufipes. The comparative analysis with data from phylogenetically related species allowed the clarification of the origin of the interspecific and intraspecific chromosome variability observed in Argyrodes and in N. rufipes, respectively.
- ItemSomente MetadadadosComparative cytogenetic analysis among filistatid spiders (Araneomorphae: Haplogynae)(Amer Arachnological Soc, 2017) Paula-Neto, Emygdio; Cella, Doralice Maria; Araujo, Douglas; Brescovit, Antonio Domingos; Schneider, Marielle Cristina [UNIFESP]The family Filistatidae is considered sister to Synspermiata or sister to Hypochilidae. Cytogenetic knowledge of this family could be useful for understanding the mechanism of chromosome evolution that has occurred within the group. In this work, two filistatid species belonging to distinct subfamilies, Kukulcania hibernalis (Hentz, 1842) (Filistatinae) and Misionella mendensis (Mello-Leitao, 1920) (Prithinae), were investigated using standard and differential chromosome staining. Analysis of mitotic and meiotic cells revealed the diploid 2n male = 25 for K. hibernalis and 2n male = 21 for M. mendensis. Both species exhibited a sex chromosome system of the X1X2Y type and metacentric/submetacentric chromosomes. In prophase I cells, the sex chromosomes were in a trivalent configuration with all elements associated without chiasma through their terminal regions. Both species revealed six nucleolar organizer regions on the terminal region of three autosomal pairs. In K. hibernalis, constitutive heterochromatin was located mainly in the terminal regions of autosomes and sex chromosomes while in M. mendensis, the heterochromatin occurred in the pericentromeric region of all chromosomes. Despite the scarcity of cytogenetic information for Filistatidae, the available results show the occurrence of high variability in the diploid number but with the maintenance of the X1X2Y sex chromosome system. Additionally, the karyotype differentiation in the species of this family seems to have involved not only the number of autosomes but also specific chromosomal sites, such as the constitutive heterochromatic regions.
- ItemSomente MetadadadosComparative Cytogenetics of Seven Ctenidae Species (Araneae)(Zoological Soc Japan, 2014-02-01) Araujo, Douglas; Oliveira, Edson Gabriel de; Giroti, Andre Marsola; Mattos, Viviane Fagundes; Paula-Neto, Emygdio; Brescovit, Antonio Domingos; Schneider, Marielle Cristina [UNIFESP]; Cella, Doralice Maria; Universidade Federal de Mato Grosso do Sul (UFMS); Universidade de São Paulo (USP); Inst Butantan; Universidade Federal de São Paulo (UNIFESP)The present study elevates the number of cytogenetically analyzed ctenid species and genera from two to eight and six, respectively, presenting comparisons between chromosomal data obtained and the phylogenetic hypothesis proposed in the literature. Six ctenid species presented 13 autosomal pairs, exhibiting either X(1)X(2)0 (Ctenus ornatus, Ctenus sp., Parabatinga brevipes and Phoneutria nigriventer) or X(1)X(2)X(3)0 sex chromosome systems (Nothroctenus sp. and Viracucha andicola). Asthenoctenus borellii showed 2n male = 20 + X(1)X(2)0. in all species, the chromosomes were telocentric. Some cells of one C. ornatus specimen exhibited one extra chromosome that, considering the behavioral similarities between the two chromosomes, can be considered to be supernumerary, derived from or giving rise to a sex chromosome. Silver impregnation revealed nucleolar organizer regions on one autosomal pair of C. ornatus and P. nigriventer (Cteninae) and two pairs of V. andicola (Acanthocteninae). Chromosomal data suggests that the X(1)X(2)X(3)0 system arose several times in the evolution of entelegyne spiders, and that conversion of an X(1)X(2)0 system into an X(1)X(2)X(3)0 system and vice-versa has been a relatively common event in spiders. All the chromosomal data corroborate the close relationship between Ctenus and Phoneutria, the placement of P. brevipes within Cteninae, the placement of Anahita in a separated branch within Cteninae, and the inclusion of A. borellii in a distinct group within the ctenids (Viridasiinae), all of which are as proposed by phylogenetic hypotheses available in the literature.