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Distribution of 6 microsatellites and 5 transposable elements on the chromosomes of Semaprochilodus taeniurus and S. insignis, commonly referred to as Jaraqui, was performed using their physical mapping with fluorescence in situ hybridization. In this study, we aim to understand the evolutionary dynamics in genomes of S. taeniurus and S. insignis by comparing the position, abundance and contribution of the repetitive sequences in the origins and differentiation of a ZZ/ZW sex chromosome system in S. taeniurus. Results revealed that distribution patterns of repetitive DNAs along the chromosomes varied considerably. Hybridization signals were observed on several autosomes in both species; however, in S. taeniurus genome, the repetitive sequences were more abundant. In addition, large clusters of known repetitive sequences were detected in sex chromosomes of S. taeniurus. This observation is notable because the accumulation of repetitive DNAs could reflect the degradation of genetic activities and the differentiation of protosex chromosomes, evolving into the heteromorphic ZW pair observed in S. taeniurus. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Interspaced repetitive DNA elements and segmental duplications have been extensively analyzed in fishes through physical chromosome mapping methods, providing a better comprehension of the structure and organization of the genome of this group. In order to contribute to this scenario, a sequence integration study of different classes of repetitive DNA with high resolution physical chromosome mapping was performed in Sorubim lima. Fluorescence in situ hybridization (FISH) and fiber-FISH with probes for 18S and 5S rRNA genes, TTAGGGn sequence and non-LTR retrotransposon family members Rex1, Rex3 and Rex6 showed that non-LTR elements may be dispersed in the chromosome set with relative concentration in heterochromatic regions, as shown by Rex1, or may even intercalate in 45S rDNA and the telomeric sequence, as found for Rex3 and Rex6. These results reinforce the presence of preferential regions of retroelement accumulation and contribute to a better understanding of the genomic organization of some repetitive DNA classes in fishes. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The Xyp sex determination mechanism is the system most frequent and ancestral to Coleoptera. Moreover, the presence of argyrophilous material associated with the sex bivalent is described as being responsible for the maintenance and association of these chromosomes. There are no karyotype data available regarding the genus Lagria and no consensus in the literature regarding the argyrophilous material present in the lumen of sex bivalent. Therefore, the aim of this work was to investigate the mechanism of sex chromosome bivalent association in Lagria villosa by analyzing the argyrophilous nature of the material present in the Xyp lumen. It was also intended to characterize L. villosa cytogenetically. The analysis of meiotic cells showed 2n = 18 = 16+Xyp for males and 2n = 18 = 16+XX in females and the meiotic formula was 2n = 8II+Xyp. The C-banding showed blocks of pericentromeric heterochromatin in all chromosomes except in the yp chromosome. In these regions, the use of fluorochromes revealed the presence of heterochromatin containing GC rich DNA sequences. The study of synaptonemal complex showed a gradual increase in the electron-density of the axial elements of the sex chromosomes and their association with strongly electron-dense material. The pepsin pretreatment revealed that the material impregnated by silver is protein. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Thrips are small insects (0.5–3.0 mm) with distinct habits and life histories characterized by haplodiploid sex determination. In general, low levels of genetic diversity have been reported in haplodiploid insects, although most reports focus on the order Hymenoptera. Therefore, we used RAPD markers to evaluate the structure and both inter- and intra-population genetic variability of Gynaikothrips uzeli (Thysanoptera: Phlaeothripidae). Six populations, three from Paraná state, southern Brazil, and three from Bahia, northeastern Brazil, were studied. Similarly to other haplodiploid insects, the genetic diversity of G. uzeli was reduced. This result is putatively related to the haplodiploid sex determination system, which yields little genetic variation, and to ecological traits of the studied species, such as the low dispersal abilities and life mode in leaf galls. All individuals were homogeneously clustered in their respective collection sites, forming two main groups in which populations from similar environments were more closely related. The analyzed populations were highly structured, and the genetic variation was higher among than within populations. [ABSTRACT FROM PUBLISHER]