Nannostomus is comprised of 20 species. Popularly known as pencilfishes the vast majority of these species lives in the flooded forests of the Amazon basin and are popular in the ornamental trade. Among the lebiasinids, it is the only genus to have undergone more than one taxonomic revision. Even so, it still possesses poorly defined species. Here, we report the results of an application of DNA barcoding to the identification of pencilfishes and highlight the deeply divergent clades within four nominal species. We surveyed the sequence variation in the mtDNA cytochrome c oxidase subunit I gene among 110 individuals representing 14 nominal species that were collected from several rivers along the Amazon basin. The mean Kimura-2-parameter distances within species and genus were 2% and 19,0%, respectively. The deep lineage divergences detected in N. digrammus, N. trifasciatus, N. unifasciatus and N. eques suggest the existence of hidden diversity in Nannostomus species. For N. digrammus and N. trifasciatus, in particular, the estimated divergences in some lineages were so high that doubt about their conspecific status is raised.

Karyotypes of six cichlid species of the genus Crenicichla were investigated. The species C. cincta, C. inpa, C. reticulata, C. lugubris, and C. cf. johanna were collected from Amazon basin, and C. britskii was collected from the Paraná-Paraguai basin. All of the analysed species showed 2n = 48 chromosomes; however, C. cincta, C. lugubris, C. cf. johanna, and C. britskii had a karyotype formula of 8M-SM+40ST-A, FN = 56, while C. inpa and C. reticulata exhibited the formula 6M-SM+42ST-A, FN = 54. Analysis of active Ag-NORs revealed two NOR-bearing chromosomes in all species; however, theses cistrons were located on different chromosome pairs and/or in different chromosome locations in each species. This condition bears evolutionary significance, since it is the main chromosome marker of the process of karyotypic evolution among the species of the genus Crenicichla. In general, C-banding revealed a similar constitutive heterochromatin pattern in all species, although it was possible to detect some features that led us to infer that Crenicichla also presents a species-specific heterochromatin pattern.

B chromosomes are reported in three different Amazonian cichlid species. One to three supernumerary microchromosomes were detected in the peacock bass Cichla monoculus (4 out of 28 specimens) and Cichla sp. (4 out of 13 specimens), and pike cichlids Crenicichla reticulata (2 out of 5 specimens), with no similar standard chromosomal morphology. C-banding revealed that B chromosomes are totally heterochromatic. We suggest two scenarios for the origin of these B chromosomes either by chromosomal breakdowns due to mutagenic action of methyl mercury present in the aquatic environment or by interspecific origin due to hybridization events.

Alzheimer disease (AD) is a complex neurodegenerative pathology that is characterized by a cognitive decline. Its causes and mechanisms are still largely unknown. It has been suggested that both genetic and life exposure factors can contribute to AD development. There are also evidences that chromosomal alterations can be related to this disease. So far, there is not a precise diagnosis for AD, which is given only after the exclusion of other dementia by clinical and neurological examination. The possible association of AD with chromosomal alterations and the easy access of classical cytogenetics analysis are important aspects to consider, given the difficulties in diagnosis. Due to the lack of similar studies in Brazil and the increasing number of AD cases in the state of Amazonas, the aim of this study was to investigate the presence of chromosomal alterations in patients diagnosed with AD in Manaus, Amazonas, Brazil. Peripheral blood lymphocytes of twelve patients and twelve healthy individuals with the same age were analyzed using conventional karyotyping. All AD patients presented cells with autosomal aneuploidy, while no chromosomal alterations were found in the age-matched controls. Also, rare events of double and multiple aneuploidies are being reported in association with AD for the first time. Our results corroborate that the increase in the frequencies of aneuploidies is not related to the aging process itself, but it might be associated to the disease development. However, no chromosomes were preferentially affected in all AD patients, and no consistent karyotype pattern for AD lymphocytes was found. Therefore, our results do not support the use of standard cytogenetics as a tool for AD diagnosis. Future studies are necessary to understand better the association between chromosomal alterations and AD.

Abstract:Chromosomal alterations are the main causes of genetic diseases. One of the characteristics of certain genetic syndromes is ID (intellectual disability) presented by the individual in varying degrees. The study of the ID, its etiology, association or not with chromosomal abnormalities and a clinical diagnosis associated with the examination of karyotype are important aspects to consider when providing genetic counseling for families. Due to the lack of similar studies and of easy access to cytogenetic services for the Amazonian population, this study aimed to contribute to the advancement of this line of study in the state, analyzing the karyotype of individuals with ID, not Down Syndrome treated at the APAE-Manaus and identifying the main types of chromosomal alterations in the individuals analyzed. Analyzes were performed of the clinical diagnosis through investigation of the data from the interview and medical records as well as analysis of the karyotype of 31 patients with non-Down syndrome ID, attended in the APAE-Manaus. Of these subjects, 20 were female and 11 male. The results showed only 2 cases of chromosome abnormalities are detectable by classical cytogenetics, one of mosaic Turner syndrome and one a heterochromatic variant. It is therefore necessary to complement the study with the addition of molecular techniques for the investigation of microdeletions and/or other alterations not detectable through the banding technique, mainly for individuals whose dysmorphisms indicate a suspected syndrome.