Chromosomal similarities and differences among four Neotropical Elateridae (Conoderini and Pyrophorini) and other related species, with comments on the NOR patterns in Coleoptera

This work deals with the comparative cytogenetic analysis of four Neotropical Elateridae species and reviews the nucleolar organizer region (NOR) patterns on Coleoptera chromosomes, for the first time. The cytogenetic characterization of Conoderus malleatus (Conoderini), Pyrearinus candelarius, Pyrophorus divergens and Pyrophorus punctatissimus (Pyrophorini) was accomplished through the study of mitotic and meiotic cells submitted to standard (Giemsa) and differential staining [silver impregnation and GC-specific chromomycin A 3 (CMA 3) plus AT-specific 4′-6-diamidino-2-phenylindole (DAPI) fluorochromes]. The analysis of spermatogonial cells revealed the diploid numbers: 2n = 17 in C. malleatus and 2n = 15 in P. candelarius, P. divergens and P. punctatissimus. In these species, the X0 type sex-determination system and the acrocentric morphology of almost all chromosomes were observed. The study of meiotic cells of the four species revealed the occurrence of total synapsis between the autosomes, the presence of one terminal or interstitial chiasma in the majority of the bivalents, and the reductional behaviour and regular segregation of all chromosomes. Although the three Pyrophorini species demonstrated many similar karyotypical characteristics, there was one discrepancy, which was noted in the diplotene cells and concerns the number of bivalents with two chiasmata; P. candelarius only presented one bivalent, P. divergens showed two bivalents and P. punctatissimus exhibited up to four bivalents with two chiasmata. Testicular cells impregnated with silver nitrate demonstrated two terminal NORs located on the fourth autosomal pair of the Conoderini species and on the second autosomal pair of the three Pyrophorini representatives. Use of CMA 3/distamycin A (DA)/DAPI staining on the P. candelarius and P. punctatissimus chromosomes revealed that the CMA 3 labelled regions were coincident with the NORs. The main strategies of karyotypical differentiation that have occurred among the four Elateridae species and other related species, and the general trends of the NOR shifts during Coleoptera chromosomal evolution are discussed in this work. © 2007 The Authors.

Differential characterization of holocentric chromosomes in triatomines (Heteroptera, Triatominae) using different staining techniques and fluorescent in situ hybridization

A comparative study of holocentric chromosomes in the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans was carried out in order to characterize heterochromatin, rDNA active sites and nucleolar proteins. Cytological preparations of seminiferous tubules were stained by silver impregnation, C banding, fluorochromes CMA 3/DA and DAPI/DA, and fluorescent in situ hybridization (FISH) with Drosophila melanogaster 28S rDNA probe. Our results showed interesting aspects of the organization of chromatin and chromosomes in the meiotic cells of these insects. In R. pallescens, sex chromosomes (X, Y) were distinct from autosomes, when submitted to silver impregnation, C banding, CMA 3 staining, and FISH, confirming that these chromosomes bear nucleolar organizer regions (NORs). In P. megistus, two of the three sex chromosomes were CMA 3/DAPI-; at early meiotic prophase and at diakinesis, silver impregnation corresponded with FISH signals, indicating that in this species, two chromosomes (probably a sex chromosome and an autosome) bear NORs. In T. infestans, silver nitrate and FISH also stained corresponding areas on meiotic chromosomes. Our data suggest that in triatomines, in general, the number and location of NORs are species-specific. These regions may be considered important chromosome markers for comparative studies to improve the understanding of evolutionary mechanisms in these hematophagous insects. ©FUNPEC-RP.

Analysis of the nucleolar cycle in the seminiferous epithelium of rodents

The nucleolus is a subcompartment of the nucleus and the site of ribosome biogenesis. During the mitotic and meiotic cell cycles, a disorganization and later reorganization of the nucleolar material occur, an event called nucleologenesis. In the spermatogenesis of mammals and other vertebrates, there is evidence of the disorganization of the nucleolus at the end of meiosis I, which supplies material for the cytoplasmic formation of an organelle called the chromatoid body (CB). The CB is a structure characteristic of spermatogenic cells and seems to be responsible for RNA metabolism in these cells and for some events of spermiogenesis, such as the formation of the acrosome, cellular communication between spermatids, and the formation of the spermatozoon middle piece and tail. The aim of this paper was to obtain information about the cytochemical and ultrastructural nature of the nucleolar cycle and the distribution of cytoplasmic RNAs in the seminiferous tubule cells of Rattus novergiucus, Mus musculus and Meriones unguiculatus. The testis was fixed in Bouin and Karnovsky solutions for conventional histological analysis and for cytochemical study that included: periodic acid-Schiff, hematoxylin-eosin, Feulgen reaction, silver-ion impregnation, Gomori's reticulin stain, toluidine blue, modified method of critical electrolyte concentration, and basic and acid fast green. The blocks of testis fixed in glutaraldehyde were used for ultrastructural analysis by transmission electron microscopy. Ultrathin sections were double-stained with uranyl acetate and lead citrate. All the techniques used provided information on the origin and function of the CB in the spermatogenic cells. Therefore, considering the persistence of the RNA and nucleolar ribonucleoproteins during spermatogenesis of Rattus novergicus, Mus musculus and Meriones unguiculatus, our findings corroborate the statement that these molecular complexes are very important in the spermiogenesis phases. It can be suggested that these ribonucleoprotein corpuscles (chromatoid bodies) are of nuclear origin and have a role in the successive series of events that occur in the formation of the spermatozoon. Furthermore, these results reinforce the conservation of the mechanisms involved in preserving necessary levels of protein stocks in different stages of cell differentiation, from spermatid to spermatozoon, in these rodent species. ©FUNPEC-RP.

Cytogenetic analysis in the spermatogenesis of Triatoma melanosoma (Reduviidae; Heteroptera)

Triatomines are of great concern in public health because they are vectors of Chagas' disease. This study presents an analysis of the species Triatoma melanosoma. The cytogenetic characteristics of triatomines include holocentric chromosomes, post-reductional meiosis in the sex chromosomes and nucleolar fragmentation in the meiotic cycle. The methodology utilized consisted of the techniques of lacto-acetic orcein staining and silver ion impregnation. The organs analyzed were adult testicles. The results enabled to classify the chromosomes by number and size, being three large, eight medium and one small heterochromosome. The three largest chromosomes and the heterochromosomes showed heteropyknotic chromatin in meiosis. The heterochromosomes in 8.05% of the cells in metaphase I behaved as pseudobivalents, contrasting with 91.95% of the cells with individualized sex chromosomes, confirming the achiasmatic nature of these chromosomes. However, the pseudobivalents occurred prominently in metaphase II (78.38%), this fact probably is related to the post-reductional nature of the sex chromosomes. The nucleolus in T. melanosoma persisted until the diplotene phase after which it began to fragment. Nucleolar corpuscles were observed in metaphases I and II and during anaphases I and II, these characteristics being related to the phenomenon of nucleolar persistence. In the initial spermatids, peripheral silver ion impregnation occurred, which could be analogous to the pre-nucleolar corpuscles observed after fragmentation. Thus, this study extends our knowledge of the characteristics of triatomines, in particular, heteropyknotic degree, kinetic activity, formation of sex chromosome achiasmatic pseudobivalency, confirmation of the fragmentation phenomenon, and post-meiotic nucleolar reactivation. ©FUNPEC-RP.

Spermatogenesis and karyotypes of three species of water striders (Gerridae, Heteroptera).

Although they are of economic importance, there have been few cytogenetic studies of the Gerridae (Heteroptera) in Brazil. We examined spermatogenesis (meiosis and spermiogenesis) and nucleolar behavior in three species of the family Gerridae. Brachymetra albinerva and Halobatopsis platensis were found to have a chromosome complement of 2n = 25 (24A + X0) and Cylindrostethus palmaris 2n = 29 (28A + X0) chromosomes. Fifteen individuals of these species were collected from the reservoir of São José do Rio Preto, SP, using screens and were transported in pots containing water to the laboratory, where cytogenetic preparations were made. The polyploidy nuclei are formed by several heteropyknotic regions; cells in meiotic prophase have a heteropyknotic region that is probably the sex chromosome, and the chromosomes from chiasmata. The spermatids are rounded and have a heteropyknotic region at the periphery of the nucleus; the sperm head is small, with a long tail. Silver impregnation of meiotic cells showed one or more disorganized bodies around the perichromosomal sheath. The round spermatids had two bodies next to each other, but these were elongated; one of the bodies remained in the head and the other migrated to the initial part of the tail at the end of spermagenesis, when the staining was no longer evident. The meiotic cells appear during spermatogenesis and have very similar silver-impregnation patterns in different species of Heteroptera.

Chromosomal characteristics and karyotype evolution of oxyopidae spiders (araneae, entelegynae)

We made a cytogenetic analysis of four species of Oxyopidae and compared it with the karyotype data of all species of this family. In Hamataliwa sp, the mitotic cells showed 2n♂ = 26+X 1X 2 and telocentric chromosomes. The 2n♂ = 28, which has been described for only one oxyopid spider, is the highest diploid number reported for this family. Peucetia species exhibited distinct karyotype characteristics, i.e., 2n♂ = 20+X 1X 2 in P. flava and 2n♂ = 20+X in P. rubrolineata, revealing interspecific chromosome variability within this genus. However, both Peucetia species exhibited telocentric chromosomes. The most unexpected karyotype was encountered in Oxyopes salticus, which presented 2n♂ = 10+X in most individuals and a predominance of biarmed chromosomes. Additionally, one male of the sample of O. salticus was heterozygous for a centric fusion that originated the first chromosomal pair and exhibited one supernumerary chromosome in some cells. Testicular nuclei of Hamataliwa sp and O. salticus revealed NORs on autosomal pairs, after silver impregnation. The majority of Oxyopidae spiders have their karyotype differentiated by both reduction in diploid number chromosome number and change of the sex chromosome system to X type; however, certain species retain the ancestral chromosome constitution 2n = 26+X1X2. The most remarkable karyotype differentiation occurred in O. salticus studied here, which showed the lowest diploid number ever observed in Oxyopidae and the second lowest registered for Entelegynae spiders. © FUNPEC-RP www.funpecrp.com.br.

Cytogenetic analysis in Thoracocharax stellatus (Kner, 1858) (Characiformes, Gasteropelecidae) from Paraguay river basin, Mato Grosso, Brazil

Thoracocharax stellatus (Characiformes, Gasteropelecidae) is a small Neotropical species of fish, widely distributed in several rivers of South America. Evidence for karyotype heteromorphysm in populations from different geographical regions has been reported for this species. In this way, populations of T. stellatus from the Paraguay River basin were cytogenetically characterized and the results were compared with other studies performed in the same species but from different basins. The results showed a diploid number of 2n = 54 for T. stellatus, with chromosomes arranged in 6 metacentric (m), 6 submetacentric (sm), 2 subtelocentric (st) and 40 acrocentric (a), for both sexes, with a simple Nucleolus Organiser Region (NOR) system reported by the techniques of silver nitrate impregnation and fluorescent in situ hybridisation (FISH) using 18S rDNA sequences as probe. The distribution of constitutive heterochromatin, observed by the C-band technique and Chromomycin A3 staining showed great similarity among the analyzed populations and consists mainly of discrete blocks in the pericentromeric and telomeric regions of most chromosomes. The presence of female heterogamety was alsoobserved indicating a ZZ/ZW system with W chromosome almost totally heterochromatic. The results also show cytogenetic diversity of the group and are useful to understand the mechanisms of karyotype evolution of the family. © Edson Lourenço da Silva et al.

Karyotype analysis of seven species of the tribe lophiohylini (Hylinae, Hylidae, Anura), with conventional and molecular cytogenetic techniques

Few species of the tribe Lophiohylini have been karyotyped so far, and earlier analyses were performed mainly with standard staining. Based on the analysis of seven species with use of routine banding and molecular cytogenetic techniques, the karyotypes were compared and the cytogenetic data were evaluated in the light of the current phylogenies. A karyotype with 2n = 24 and NOR in the chromosome 10 detected by Ag-impregnation and FISH with an rDNA probe was shared by Aparasphenodon bokermanni Miranda-Ribeiro, 1920, Itapotihyla langsdorffii (Duméril and Bibron, 1841), Trachycephalus sp., T. mesophaeus (Hensel, 1867), and T. typhonius (Linnaeus, 1758). Phyllodytes edelmoi Peixoto, Caramaschi et Freire, 2003 and P. luteolus (Wied-Neuwied, 1824) had reduced the diploid number from 2n = 24 to 2n = 22 with one of the small-sized pairs clearly missing, and NOR in the large chromosome 2, but the karyotypes were distinct regarding the morphology of chromosome pairs 4 and 6. Based on the cytogenetic and phylogenetic data, it was presumed that the chromosome evolution occurred from an ancestral type with 2n = 24, in which a small chromosome had been translocated to one or more unidentified chromosomes. Whichever hypothesis is more probable, other rearrangements should have occurred later, to explain the karyotype differences between the two species of Phyllodytes Wagler, 1830. The majority of the species presented a small amount of centromeric C-banded heterochromatin and these regions were GC-rich. The FISH technique using a telomeric probe identified the chromosome ends and possibly (TTAGGG)n-like sequences in the repetitive DNA out of the telomeres in I. langsdorffii and P. edelmoi. The data herein obtained represent an important contribution for characterizing the karyotype variability within the tribe Lophiohylini scarcely analysed so far. © Simone Lilian Gruber et al.

Optically transparent membrane based on bacterial cellulose/ polycaprolactone

Optically transparent membranes from bacterial cellulose (BC)/polycaprolactone (PCL) have been prepared by impregnation of PCL acetone solution into dried BC membranes. UV-Vis measurements showed an increase on transparency in BC/PCL membrane when compared with pristine BC. The good transparency of the BC/PCL can be related to the presence of BC nanofibers associated with deposit of PCL nano-sized spherulites which are smaller than the wavelength of visible light and practically free of light scattering. XRD results show that cellulose type I structure is preserved inside the BC/PCL membrane, while the mechanical properties suggested indicated that PCL acts as a plasticizer for the BC membrane. The novel BC/PCL membrane could be used for preparation of fully biocompatible flexible display and biodegradable food packaging.

Lower Permian stems as fluvial paleocurrent indicators of the Parnaíba Basin, northern Brazil

A comprehensive biostratinomic study was carried out with abundant stems from the Lower Permian Motuca Formation of the intracratonic Parnaíba Basin, central-north Brazil. The fossils represent a rare tropical to subtropical paleofloristic record in north Gondwana. Tree ferns dominate the assemblages (mainly Tietea, secondarily Psaronius), followed by gymnosperms, sphenophytes, other ferns and rare lycophytes. They are silica-permineralized, commonly reach 4 m length (exceptionally more than 10 m), lie loosely on the ground or are embedded in the original sandstone or siltstone matrix, and attract particular attention because of their frequent parallel attitudes. Many tree fern stems present the original straight cylindrical to slightly conical forms, other are somewhat flattened, and the gymnosperm stems are usually more irregular. Measurements of stem orientations and dimensions were made in three sites approximately aligned in a W-E direction in a distance of 27.3 km at the conservation unit Tocantins Fossil Trees Natural Monument In the eastern site, rose diagrams for 54 stems indicate a relatively narrow azimuthal range to SE. These stems commonly present attached basal bulbous root mantles and thin cylindrical sandstone envelopes, which sometimes hold, almost adjacent to the lateral stem surface, permineralized fern pinnae and other small plant fragments. In the more central site, 82 measured stems are preferentially oriented in the SW-NE direction, the proportion of gymnosperms is higher and cross-stratification sets of sandstones indicate paleocurrents mainly to NE and secondarily to SE. In the western site, most of the 42 measured stems lie in E-W positions. The predominantly sandy succession, where the fossil stems are best represented, evidences a braided fluvial system under semiarid conditions. The low plant diversity, some xeromorphic features and the supposedly almost syndepositional silica impregnation of the plants are coherent with marked dry seasons. Thick mudstones and some coquinites below and above the sandy interval may represent lacustrine facies formed in probably more humid conditions. The taphonomic history of the preserved plants began with exceptional storms that caused fast-flowing high water in channels and far into the floodplains. In the eastern site region, many tree ferns only fell, thus sometimes covering and protecting plant litter and leaves from further fragmentation. Assemblages of the central and western sites suggest that the trees were uprooted and transported in suspension (floating) parallel to the flow. Heavier ends of stems (according to their form or because of attached basal bulbous root mantle or large apical fronds) were oriented to upstream because of inertial forces. During falling water stage, the stems were stranded on riverbanks, usually maintaining the previous transport orientation, and were slightly buried. The perpendicular or oblique positions of some stems may have been caused by interference with other stems or shallow bars. Rare observed stems were apparently waterlogged before the final depositional process and transported as bedload. The differences of interpreted channel orientations between the three sites are expected in a braided fluvial system, considering the very low gradients of the basin and the work scale in the order of tens of kilometers. The mean direction of the drainage probably was to east and the flows apparently became weaker downstream. This study seems to provide reliable data for paleocurrent interpretations, especially considering areas with scarce preserved sedimentary structures. © 2013 Elsevier Ltd.

Cytogenetic analysis of Phyllomedusa distincta Lutz, 1950 (2n = 2x = 26), P. tetraploidea Pombal and Haddad, 1992 (2n = 4x = 52), and their natural triploid hybrids (2n = 3x = 39) (Anura, Hylidae, Phyllomedusinae)

Background: Natural polyploidy has played an important role during the speciation and evolution of vertebrates, including anurans, with more than 55 described cases. The species of the Phyllomedusa burmeisteri group are mostly characterized by having 26 chromosomes, but a karyotype with 52 chromosomes was described in P. tetraploidea. This species was found in sintopy with P. distincta in two localities of São Paulo State (Brazil), where triploid animals also occur, as consequence of natural hybridisation. We analyse the chromosomes of P. distincta, P. tetraploidea, and their triploid hybrids, to enlighten the origin of polyploidy and to obtain some evidence on diploidisation of tetraploid karyotype.Results: Phyllomedusa distincta was 2n = 2x = 26, whereas P. tetraploidea was 2n = 4x = 52, and the hybrid individuals was 2n = 3x = 39. In meiotic phases, bivalents were observed in the diploid males, whereas both bivalents and tetravalents were observed in the tetraploid males. Univalents, bivalents or trivalents; metaphase II cells carrying variable number of chromosomes; and spermatids were detected in the testis preparations of the triploid males, indicating that the triploids were not completely sterile. In natural and experimental conditions, the triploids cross with the parental species, producing abnormal egg clutches and tadpoles with malformations. The embryos and tadpoles exhibited intraindividual karyotype variability and all of the metaphases contained abnormal constitutions. Multiple NORs, detected by Ag-impregnation and FISH with an rDNA probe, were observed on chromosome 1 in the three karyotypic forms; and, additionally, on chromosome 9 in the diploids, mostly on chromosome 8 in the tetraploids, and on both chromosome 8 and 9 in the triploids. Nevertheless, NOR-bearing chromosome 9 was detected in the tetraploids, and chromosome 9 carried active or inactive NORs in the triploids. C-banding, base-specific fluorochrome stainings with CMA3 and DAPI, FISH with a telomeric probe, and BrdU incorporation in DNA showed nearly equivalent patterns in the karyotypes of P. distincta, P. tetraploidea, and the triploid hybrids.Conclusions: All the used cytogenetic techniques have provided strong evidence that the process of diploidisation, an essential step for stabilising the selective advantages produced by polyploidisation, is under way in distinct quartets of the tetraploid karyotype. © 2013 Gruber et al.; licensee BioMed Central Ltd.

Chromosomal characteristics of a Brazilian whip spider (Amblypygi) and evolutionary relationships with other arachnid orders

We analyzed mitotic and meiotic cells of a Brazilian amblypygid, Heterophrynus longicornis, using conventional and molecular cytogenetic techniques (Giemsa staining, C-banding, Ag-NOR, and FISH with rDNA probe). This is the first study that focuses solely on amblypygid chromosomes; it was undertaken to add data on cytogenetic knowledge of this group and contribute to the understanding of chromosome evolution in the Arachnida. We found 2n = 66 for male and female individuals, monocentric chromosomes, and absence of morphologically differentiated sex chromosomes. C-banding showed heterochromatin in the pericentromeric region of most chromosomes. Mitotic and meiotic nuclei submitted to silver impregnation and FISH revealed, respectively, Ag-NORs and ribosomal genes in the terminal region of two chromosome pairs. Most chromosome features that we observed in H. longicornis are shared with species of other arachnid orders; however, the absence of morphologically differentiated sex chromosomes in amblypygid contrasts with the remarkable variety of sex chromosome systems recorded for the Araneae. Consequently, we conclude that analysis of species of the Tetrapulmonata clade is useful for understanding the trends of sex chromosome evolution in this arachnid group. © FUNPEC-RP.

Flexible magnetic membranes based on bacterial cellulose and its evaluation as electromagnetic interference shielding material

Flexible magnetic membranes with high proportion of magnetite were successfully prepared by previous impregnation of the never dried bacterial cellulose pellicles with ferric chloride followed by reduction with sodium bisulfite and alkaline treatment for magnetite precipitation. Membranes were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating magnetometer, field emission scanning electron microscopy (FEG-SEM) and impedance spectroscopy. Microwave properties of these membranes were investigated in the X-band (8.2 to 12.4 GHz). FEG-SEM micrographs show an effective coverage of the BC nanofibers by Fe 3O4 nanoparticles. Membranes with up to 75% in weight of particles have been prepared after 60 min of reaction. Magnetite nanoparticles in the form of aggregates well adhered to the BC fibers were observed by SEM. The average crystal sizes of the magnetic particles were in the range of 10 ± 1 to 13 ± 1 nm (estimated by XRD). The magnetic particles in the BC pellicles presented superparamagnetic behavior with a saturation magnetization in the range of 60 emu g- 1 and coercive force around 15 Oe. These magnetic pellicles also displayed high electrical permittivity and a potential application as microwave absorber materials. © 2013 Elsevier B.V.

Paratrichodina africana (Ciliophora): A pathogenic gill parasite in farmed Nile tilapia

Trichodinids are ciliated protozoa that are widely known as one of the main groups of fish parasites. The genus Trichodina presents the greatest species diversity. However, records of Paratrichodina species are scarce, and little is known about their pathogenicity in hosts. The present study provides new records of Paratrichodina africana Kazubski and El-Tantawy (1986) in Nile tilapia from South America and descriptions of pathological changes and seasonality. A total of 304 farmed fish were examined. From gill scraping, parasites were identified using Klein's nitrate impregnation method. Gill samples were fixed for histopathological analysis. Small trichodinid found in this study have a prominent blade apophysis and narrow central part and blade shape that corresponds to the characteristics of P. africana Kazubski and El-Tantawy (1986). Gill lesions were proportional to parasite intensity, in which the gill tissue was compromised in heavy infestation. Proliferative disturbances were found, including epithelial hyperplasia, desquamation, and mononuclear and eosinophilic infiltrate that culminated in necrosis. We did not observe a seasonality effect on the occurrence of P. africana. This ciliated protozoan causes compromised respiratory capacity that leads to severe gill lesions and currently is an important pathogen that afflicts intensive tilapia cultures in Brazil. © 2013 Elsevier B.V.

Propriedades físicas de um latossolo vermelho manejado com material orgânico e submetido à compactação

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)