Comparative cytogenetic patterns in Carangidae fishes in association with their distribution range

Carangidae are an important and widespreaded family of pelagic predatory fishes that inhabit reef regions or open ocean areas, some species occupying a vast circumglobal distribution. Cytogenetic comparisons among representatives of its different tribes help to understand the process of karyotype divergence in marine ecosystems due to the variable migratory ability of species. In this sense, conventional cytogenetic investigations (Giemsa staining, Ag-NORs, and C-banding), GC base-specific fluorochrome staining and FISH mapping of ribosomal DNAs were performed. Four species, Elagatis bipinnulata (Quoy et Gaimard, 1825) and Seriola rivoliana (Valenciennes, 1883) (Naucratini), with circumtropical distributions, Gnathanodon speciosus (Forsskål, 1775) (Carangini), widely distributed in the tropical and subtropical waters of the Indian and Pacific oceans, and Trachinotus carolinus (Linnaeus, 1766) (Trachinotini), distributed along the western Atlantic Ocean, were analyzed, thus encompassing representatives of three out its four tribes. All species have diploid chromosome number 2n = 48, with karyotypes composed mainly by acrocentric chromosomes (NF = 50–56). The 18S rDNA/Ag-NORs/GC+ and 5S rDNA loci were located on chromosomes likely homeologs. Karyotypes showed a pattern considered basal for the family or with small variations in their structures, apparently due to pericentric inversions. The migratory capacity of large pelagic swimmers, in large distribution areas, likely restricts the fixation of chromosome changes in Carangidae responsible for a low level of karyotype diversification.

Comparative Cytogenetic Analysis of Three Eumeninae Species (Hymenoptera, Vespidae)

Eumeninae represents the largest subfamily within Vespidae, with 3,600 species described. Of these, only 18 have been cytogenetically analysed. In the present study, we used both classical and molecular techniques to characterise and compare the karyotypes of 3 Eumeninae species, namely, <i>Ancistrocerus</i> sp., <i>Pachodynerus grandis,</i> and <i>Pachodynerus nasidens</i>. <i>Ancistrocerus</i> sp. presented a haploid chromosome number of n = 12, with the first 2 chromosomes of the karyotype being almost entirely heterochromatic and much larger than the remaining chromosomes. The 2 <i>Pachodynerus</i> species presented the same chromosome number (n = 11 and 2n = 22) but displayed different karyotypic formulae<i>.</i> Additionally, chromosomal polymorphisms were observed in the analysed <i>P. nasidens</i> female. In the 3 species, heterochromatin was located in one of the chromosome arms. Fluorochrome staining revealed a balanced composition of AT and GC bases within the chromatin for each of the 3 species, except for few regions that were visibly GC-rich. All species had a single 18S rDNA site that co-localised with GC-rich regions; however, this localisation varied from species to species and not all GC-rich regions corresponded to ribosomal genes. Based on the cytogenetic data obtained here, we discuss the possible numerical/structural rearrangements that may be involved in the karyotypic evolution of the 3 studied species. In addition to the first description of the molecular cytogenetic characteristics of the Eumeninae subfamily and the genus <i>Pachodynerus</i>, this study also provides a relevant contribution towards the discussion of chromosomal evolution in Eumeninae wasps.

Molecular cytogenetics insights in two pelagic big-game fishes in the Atlantic, the tarpon, Megalops atlanticus (Elopiformes: Megalopidae), and the sailfish, Istiophorus platypterus (Istiophoriformes: Istiophoridae)

Some pelagic and usually large sized fishes are preferential targets for sport and commercial fishing. Despite their economic importance, cytogenetic data on their evolutionary processes and management are very deficient, especially due to logistical difficulties. Here, information for two of such charismatic species, the tarpon, Megalops atlanticus (Elopiformes: Megalopidae), and the sailfish, Istiophorus platypterus (Istiophoriformes: Istiophoridae), both with a wide Atlantic distribution, were provided. Cytogenetic data were obtained using conventional methods (Giemsa staining, Ag-NORs technique, and C-banding), base-specific fluorochrome staining and fluorescence in situ hybridization (FISH) with rDNA probes. Megalops atlanticus has 2n = 50 chromosomes, all acrocentric ones (NF = 50), while Istiophorus platypterus has 2n = 48 chromosomes, 2m + 2st + 44a (NF = 52). Megalops atlanticus populations from the South Atlantic and Caribbean share identical karyotypic patterns, likely associated with gene flow between them. In turn, I. platypterus presents karyotype similarities with phylogenetically close groups, such as Carangidae. The chromosomal characteristics of these species highlight their independent evolutionary paths. Additionally, the current data contribute to knowledge of new aspects of pelagic fish fauna and will support further comparative studies with congeneric species, clarifying evolutionary karyotype trends of these fish groups.

First Record of a B Chromosome in Polybia fastidiosuscula Saussure (Vespidae) and Investigation of Chromatin Composition Through Microsatellite Mapping

The characterization of karyotypes is an important aspect in understanding the structure and evolution of genomes. Polybia is a genus of social wasps of the family Vespidae. This genus has 58 species, but for only 8 of these chromosome number and morphology have been reported in the literature. The aim of this study was to describe and characterize the Polybia fastidiosuscula Saussure karyotype, presenting the first case of a B chromosome in Vespidae. In addition, we investigated the chromatin composition of this species through C-banding, base-specific fluorochrome staining, and physical mapping of 7 microsatellites and 18S rDNA. Four colonies of P. fastidiosuscula from Minas Gerais and Paraná states, Brazil, were analyzed. The chromosome number identified was 2n = 34, and 2 colonies presented a B chromosome. We characterized the chromatin composition of this species, analyzing the existence of different microsatellite-rich heterochromatic regions which are also enriched with AT or GC base pairs. We suggest an intraspecific origin of the B chromosome based on the homology of the heterochromatic composition with A chromosomes and also verify that the TTAGG and TCAGG sequences are not telomeric, but only microsatellites that occur in the centromeres of most chromosomes, as well as GAG and CGG.

Sensitivitas Metode Pemeriksaan Mikroskopis Fluorokrom dan Ziehl-Neelsen untuk Deteksi Mycobacterium tuberculosis pada Sputum

<p class="AbstractNormal"><em>Background: Detection of fast acid bacteria (FAB) using smear microscopy is used as a primary screening for tuberculosis diagnosis. Previous studies have shown that fluorochrome </em>(<em>Auroamine-rhodamine</em>) <em>staining showed better sensitivity compared to Ziehl-Neelsen (ZN) method in the detection of FAB in sputum. However this method has not been recommended for routine use including in Indonesia. This study aimed to evaluate the sensitivity and specificity of fluorochrome compared to ZN to detect FAB in patient’s sputum.</em><em></em></p><p class="AbstractNormal"><em>Methods: </em><em>This study analyzed 60 sputum samples from patients with tuberculosis and suspected pulmonary tuberculosis. Samples were obtained consecutively from microbiology laboratory</em><em> Moewardi Hospital, Indonesia. Each sample was examined using ZN and fluorochrome staining and cultured in Lowenstein-Jensen (LJ) medium.</em><em> Data were analyzed using sensitivity and spesificity tests.</em></p><p class="AbstractNormal"><em>Results: ZN staining detected FAB in 12 samples (10%), while fluorochrome detected FAB in 17 samples (28%). The sensitivity and specificity of ZN staining were 70% and 90% while these for fluorochrome were 90% and 84%. </em><em></em></p><p class="AbstractNormal"><em>Conclusions: The sensitivity of fluorochrome staining is better compared to ZN staining. This method can be recommended for early detection of tuberculosis.</em><em></em></p><p class="AbstractNormal"><em> </em></p>

Paracentric Inversions Differentiate the Conservative Karyotypes in Two Centropomus Species (Teleostei: Centropomidae)

Centropomus is the sole genus of the Centropomidae family (Teleostei), comprising 12 species widely distributed throughout the Western Atlantic and Eastern Pacific, with 6 of them occurring in the Western Atlantic in extensive sympatry. Their life history and phylogenetic relationships are well characterized; however, aspects of chromosomal evolution are still unknown. Here, cytogenetic analyses of 2 Centropomus species of great economic value (C. undecimalis and C. mexicanus) were performed using conventional (Giemsa, Ag-NOR, and fluorochrome staining, C- and replication banding) and molecular (chromosomal mapping of 18S and 5S rDNA, H2A-H2B and H3 hisDNA, and (TTAGGG)n repeats) approaches. The karyotypes of both species were composed of 48 solely acrocentric chromosomes (2n = 48; FN = 48), but the single ribosomal site was located in varying positions in the long arms of the second largest chromosome pair. Replication bands were generally similar, although conspicuous differences were observed in some chromosome regions. In both species, the histone H3 genes were located on 3 apparently homeologous chromosome pairs, but the exact position of these clusters differed slightly. Interspecific hisDNA and rDNA site displacements can indicate the occurrence of multiple paracentric inversions during the evolutionary diversification of the Centropomus genomes. Although the karyotypes remained similar in both species, our data demonstrate an unsuspected microstructural reorganization between them, driven most likely by a series of paracentric inversions.

Comparative molecular cytogenetics in Melipona Illiger species (Hymenoptera, Apidae)

Cytogenetic studies in Melipona are scarce with only 24 species analyzed cytogenetically. Of these, six species had the rDNA sites physically mapped and characterized by Fluorescent in situ Hybridization (fish). The aim of this study was to perform karyotype analyzes on Melipona species from different regions of Brazil, with a greater sampling representative of the Amazonian fauna and using conventional, fluorochrome staining and FISH with heterologous rDNA probes. The predominant chromosome number was 2n = 18, however, the subspecies M. seminigra abunensis and M. s. pernigra showed 2n = 22 chromosomes. The karyotypes were symmetrical, however M. bicolor, M. quadrifasciata, M. flavolineata, M. fuscopilosa, M. nebulosa presented the first pair heteromorphic in length. CMA3+ blocks also exhibited heteromorphism of size and in almost all cases coincided with rDNA sites, except for M. crinita and M. nebulosa, which presented additional non-coincident CMA3+ blocks. The CMA/ rDNA sites were terminal and interstitial in species with high heterochromatic content, and pericentromeric in those species with low heterochromatic content. In addition to pointing out cytogenetic features of cytotaxonomic importance, the reorganization of the genome in Melipona is discussed.

Loop-Mediated Isothermal Amplification Assay for Rapid and Reliable Detection of Mycobacterium tuberculosis in Sputum Samples

Introduction: Tuberculosis (TB) remains a major global health problem. The most common method for diagnosing TB in developing countries is sputum smear microscopy; however, the sensitivity of this test is relatively lower. Detection of Mycobacterium tuberculosis using conventional culture and biochemical-based assays is time-consuming and laborious. Polymerase Chain Reaction (PCR) is also available for diagnosis of Mycobacterium tuberculosis. However, the PCR assay requires an expensive thermal cycler to amplify the DNA fragment in multiple temperature-dependent steps. Therefore, a simple and sensitive method for rapid detection has been anxiously awaited. The loop-mediated isothermal amplification (LAMP) assay is a diagnostic technique which can aid in the fight against TB in resource-poor countries. The LAMP assay can amplify a targeted sequence at a constant temperature. Therefore, a large and costly thermal cycler is not necessary for a LAMP assay.Objectives: The objective of this study was to identify Mycobacterium tuberculosis directly from sputum by LAMP and to compare its efficacy over routinely used methods.Methods: A total of 106 (53 fluorochrome staining positive and 53 fluorochrome staining negative) sputum samples were collected in this study. Mycobacterial DNA was extracted from concentrated sputum samples by freezing and boiling method. LAMP assay using a set of six specific primers targeting the M. tuberculosis 16S rRNA gene with high sensitivity was used to analyze sputum samples. The results were then compared with that of the culture method, which was considered as the gold standard method.Results: Among total of 106 samples studied by microscopy and culture, 53 were positive by both, whole four were positive by culture but negative by microscopy. With reference to culture, the microscopy had sensitivity 92.98%, specificity 100%, and predictive value of positive test 100%, predictive value of negative test 92.5%. Out of 106 samples subjected to culture and LAMP for the diagnosis of TB, 55 samples were positive by both tests and two were positive only in culture, while 48 were negative in both tests and one was negative only in culture. While comparing the LAMP with culture as a gold standard, the sensitivity of LAMP was 96.49%, specificity was 97.95%, predictive value of positive test was 98.21%, predictive value of negative test was 96%.Conclusions: Comparative experiments showed that the LAMP assay is a rapid, sensitive, and specific method to detect M. tuberculosis infection. Indeed, an inexpensive LAMP assay would be potential as a diagnostic test for tuberculosis, especially in resource-limited settings. J-GMC-N | Volume 11 | Issue 01 | January-June 2018, Page: 27-34