Abstract Chromosomal polymorphisms have been reported in numerous vertebrates, including fishes. Such variation is usually related to karyoevolutionary trends and speciation but might also be a result of environmental stress. Herein, we provide the first karyotype characterization in populations of a widespread small characin (Hemigrammus marginatus) from an impacted river basin in Northeastern Brazil to infer their chromosome organization and putative genotoxic effects. Therefore, we reported intra and interindividual structural polymorphism and multiple active nucleolar organizer regions in samples from Contas River, a highly polluted environment when compared to less impacted areas. Furthermore, this report represents the first description of chromosomal mosaicism in the family Characidae so far. Besides revealing peculiar karyotypic patterns in relation to populations from other basins, our results suggest that the chromosomal instability in specimens H. marginatus might be associated with the presence of xenobiotics in polluted environments. vertebrates fishes stress Herein Hemigrammus effects Therefore River areas Furthermore far basins H environments

Abstract Molecular species delimitation methods are efficient tools to identify species, including the discovery of new taxa and cryptic organisms, thus being useful to biodiversity studies. In the present work, 16S mitochondrial sequences and cytochrome oxidase I (COI) were used to evaluate the richness of species in the genus Scinax and Ololygon from a biodiversity hotspot in Atlantic Forest. A total of 109 specimens formally belonging to eight species of Scinax and three species of Ololygon were collected in 13 localities along the state of Bahia (northeastern Brazil) and one site in Espírito Santo (southeastern Brazil). Of the Scinax species collected in this study, three were morphologically differentiated from other described species and identified as putative new species (Scinax sp.1, Scinax sp.2 and Scinax sp.3). The species delimitations were inferred using three different methods: ABGD, PTP and mPTP which allowed recognizing 11 Scinax species and five Ololygon species. Scinax sp. 1, Scinax sp. 2 and Scinax sp. 3, have been confirmed as new putative species and Ololygon argyreornata possibly contains cryptic species. We suggest additional studies, including morphological and bioacoustic data to validate these new putative species.

Abstract Scinax (Anura: Hylidae) is a species-rich genus of amphibians (113 spp.), divided into five species groups by morphological features. Cladistic analyses however revealed only two monophyletic clades in these groups: Scinax catharinae and Scinax ruber. Most species from the S. catharinae clade are found in Atlantic rainforest, except for Scinax canastrensis,S. centralis, S. luizotavioi, S. machadoi,S. pombali and S. skaios. In the present work, specimens of Scinax collected in Chapada dos Guimarães, central Brazil, were morphologically compatible with species from theS. catharinae group. On the other hand, genetic analysis based on mitochondrial (16S and 12S) and nuclear (rhodopsin) sequences revealed a nucleotide divergence of 6 to 20% between Scinax sp. and other congeners from the Brazilian savannah (Cerrado). Accordingly, Bayesian inference placed Scinax sp. in the S. catharinae clade with high support values. Hence, these findings strongly indicate the presence of a new species in the S. catharinae clade from the southwestern portion of the Brazilian savannah. To be properly validated as a novel species, detailed comparative morphological and bioacustic studies with other taxa from Brazil such asS. canastrensis, S. centralis, S. luizotavioi, S. machadoi, S. pombali and S. skaios are required.

Scinax species are still underrepresented in cytogenetic studies, mainly with respect to populations from northeastern and northern Brazil. In this study, we provide new chromosomal information on Scinax boesemani, S. camposseabrai, S. garbei, S. pachycrus, S. trilineatus and S. x-signatus, all belonging to clade S. ruber. They were collected at two locations in the Caatinga biome (northeastern Brazil) and at one in the Amazon (northern Brazil) biomes. Chromosomes were analyzed by conventional staining, C-banding, Ag-NOR staining, and fluorochrome staining. All species shared a modal diploid value of 2n = 24 and fundamental arm number (FN) of 48. Moreover, both chromosomal size and morphology were similar to other species in this Scinax clade. C-banding revealed centromeric heterochromatin in all species, along with terminal species-specific C-bands in some species. Active nucleolar organizer regions (Ag-NORs) were identified at 11q in most species, except for S. boesemani and S. garbei (Ag-NORs at interstitial region of 8q). Differing from most anurans, GC-rich regions were not restricted to NORs, but also coincident with some centromeric and terminal C-bands. These data contribute to the cytotaxonomy of Scinax by providing chromosomal markers and demonstrating the occurrence of microstructural rearrangements and inversions on chromosomal evolution of Scinax.

Parrotfishes (Labridae, Scarinae) comprise a large marine fish group of difficult identification, particularly during juvenile phase when the typical morphology and coloration of adults are absent. Therefore, the goal of this study was to test cytogenetic markers and DNA barcoding in the identification of bucktooth parrtotfish Sparisoma radians from the northeastern coast of Brazil. Sequencing of cytochrome c oxidase subunit I (COI) confirmed all studied samples as S. radians, and all showed high similarity (99-100%) with Caribbean populations. The karyotype of this species was divergent from most marine Perciformes, being composed of 2n = 46 chromosomes. These consisted of a large number of metacentric and submetacentric pairs with small amounts of heterochromatin and GC-rich single nucleolar organizer regions (NORs) not syntenic to 5S rDNA clusters. These are the first data about DNA barcoding in parrotfish from the Brazilian province and the first refined chromosomal analysis in Scarinae, providing useful data to a reliable genetic identification of S. radians.

The fish genus Astyanax is widespread throughout the Neotropical region and is one of the most species-rich genera of the Characiformes. Cytogenetic studies of Astyanax have revealed marked intra-and interspecific diversity, with the identification of various species complexes. In this report, we describe the karyotypic structure of two sympatric species of Astyanax (Astyanax sp. and Astyanax aff. fasciatus) from the Middle Contas River basin in the northeastern Brazilian state of Bahia. Both species had 2n = 48 but differed in their karyotypic formulae. Small heterochromatic blocks and multiple nucleolar organizer regions (NORs) were identified in both species. Terminal CMA3+/DAPI-signals were observed in Astyanax sp. and A. aff. fasciatus, mostly coincident with NORs. These results show that chromosomal markers can be used to identify species in this fish complex. These markers can provide useful information for evolutionary studies and investigations on the mechanisms of chromosomal diversity in Astyanax.

A espécie Hoplias malabaricus é um predador que ocorre em praticamente todas as bacias cis-andinas. Sob o ponto de vista citogenético, ela compreende, pelo menos, sete cariomorfos diferenciáveis. Várias localidades já foram previamente analisadas no Brasil, porém, algumas regiões, como o Estado da Bahia, permanecem pouco amostradas. Recentemente, o Ministério de Meio Ambiente classificou as bacias do rio Itapicuru e Contas (inteiramente localizadas na Bahia), como áreas prioritárias de conservação, cuja biodiversidade carece de informações suficientes. Neste sentido, o objetivo do presente trabalho foi caracterizar citogeneticamente populações de H. malabaricus nessas bacias, por meio de técnicas de coloração convencional, Ag-RON e bandamento C. Todos os espécimes e populações analisadas apresentaram número diploide 2n = 40 com cromossomos metacêntricos/submetacêntricos, sem diferenças entre os sexos, representando assim o denominado "cariomorfo F". O primeiro par metacêntrico apresentou tamanho notavelmente maior que os demais pares. As RONs foram múltiplas, ocupando a região terminal do braço longo de dois pares cromossômicos em ambas populações. Entretanto, os padrões de heterocromatina foram relativamente diferenciáveis entre as bacias hidrográficas estudadas. Apesar de compartilharem blocos heterocromáticos na região centromérica de todos os cromossomos, a população da bacia do Itapicuru apresentou alguns blocos mais conspícuos em relação aos da bacia do rio de Contas. O cariótipo similar encontrado em ambas as populações parece indicar uma história geológica em comum. Os dados obtidos representam um avanço no conhecimento dos padrões citogenéticos de populações de H. malabaricus provenientes de bacias pouco estudadas

The species Hoplias malabaricus is a predator fish found in nearly all cis-Andean basins. From a cytogenetic point of view, this species comprises, at least, seven differentiated karyomorphs. Several localities have been formerly analyzed in Brazil, however, some regions, such as Bahia State, remain underrepresented. Recently, the Brazilian Environment Ministry classified both Itapicuru and Contas river basins (entirely located within Bahia territory) as priority conservation areas, whose biodiversity status lacks enough information. Therefore, the goal of the present work was to characterize, cytogenetically, populations of H. malabaricus from both basins, by using conventional staining, Ag-NOR and C-banding techniques. All specimens presented a diploid number of 2n = 40 with metacentric/submetacentric chromosomes, without differences between sexes, thereby representing the so-called "karyomorph F". The first metacentric pair presented a remarkably larger size in relation to the other pairs. The NORs were multiple, comprising the terminal region on long arms of two chromosomal pairs in both populations. However, the C-banding pattern was somewhat distinguishable between samples. Although sharing heterochromatic blocks at centromeric region of all chromosomes, the population from Itapicuru River basin appeared to have some more conspicuous blocks than those observed in the population from Contas River basin. The similar karyotype observed in both populations suggests a common geological history between them. The present results represent an advance in the knowledge about the cytogenetic pattern of H. malabaricus populations from poorly studied basins.

Poucos estudos ictiofaunísticos estão disponíveis em rios típicos do semi-árido, apesar da constante ameaça à diversidade local devido a influências antrópicas, com destaque para o represamento e construção de barragens. O presente trabalho teve como objetivo avaliar, por meio de diferentes metodologias, a estrutura genética de populações de uma espécie de caracídeo, Astyanax aff. bimaculatus, amplamente distribuída em bacias hidrográficas da Bahia, Nordeste do Brasil. Análises morfológicas (dados merísticos e morfométricos), citogenéticas (cariótipo e Ag-RONs) e moleculares (RAPD e SPAR) foram realizadas em espécimes coletados à montante e à jusante da Barragem da Pedra, na calha principal do médio rio de Contas (bacia do Rio de Contas) e no ribeirão Mineiro, pertencente à bacia adjacente do Recôncavo Sul. Poucas diferenças externas foram detectadas entre as populações, sendo os indivíduos originários do reservatório, à montante da barragem, ligeiramente maiores. Os dados citogenéticos também mostraram padrões cariotípicos semelhantes (2n=50; 6m+28sm+12st+4a; FN= 96) e RONs situadas nos braços curtos de até dois pares cromossômicos, com variação numérica inter- e intra-populacional. Contudo, as análises por RAPD e SPAR diferenciaram as três populações de forma eficiente, revelando freqüências alélicas significativamente diferentes entre as localidades amostradas e índices significativos de estruturação populacional (Fst=0.1868, P<0.0001). As diferenças entre populações do mesmo rio foram tão significativas quanto entre bacias hidrográficas distintas, indicando que a represa constitui uma barreira eficiente ao fluxo gênico. Além disso, acredita-se que peculiaridades ambientais de cada localidade possam também influenciar os padrões genéticos encontrados. Por outro lado, a similaridade entre amostras das bacias do Rio de Contas e Recôncavo Sul pode estar relacionada a uma história evolutiva comum, já que ambas estão geograficamente próximas. Por fim, o presente estudo demonstra que a realização de estudos envolvendo diferentes marcadores é extremamente útil para a identificação de estruturas de populações em espécies amplamente distribuídas e para avaliação dos impactos das atividades humanas sobre as populações naturais de peixes.

Few reports are available about the ichthyofauna of typical semi-arid rivers, although the regional diversity has been constantly threatened by human activities, mainly related to impoundment and construction of dams. The goal of the present work was to evaluate using different methods, the population genetic structure of a characin fish, Astyanax aff. bimaculatus, widespread throughout hydrographic basins of Bahia, Northeastern Brazil. Morphological (meristic and morphometric data), cytogenetic (karyotype and Ag-NOR), and molecular (RAPD and SPAR) analyses were carried out in specimens collected upstream and downstream of Pedra Dam, in the main channel of Contas River (Contas River Basin), and in the Mineiro stream, which belongs to the adjacent Recôncavo Sul basin. Few external differences were detected among populations, where the individuals collected upstream of Pedra Dam were slightly larger than the others. Cytogenetic data also showed a similar karyotypic pattern (2n=50; 6m+28sm+12st+4a; FN= 96) and NORs located on the short arms of up to two chromosome pairs, with numerical inter- and intra-populational variation. Nonetheless, RAPD and SPAR analyses differentiated reliably the three populations, revealing striking differences in the allele frequencies among the localities studied and a significant difference in population structure index (Fst=0.1868, P<0.0001). The differences between populations within a same river were as significant as those between distinct hydrographic basins, indicating that the dam/reservoir represents an effective barrier to gene flow. Additionally, environmental peculiarities from each locality are also believed to influence the genetic patterns detected herein. On the other hand, the similarity between samples from Contas River and Recôncavo Sul basins could be related to a common evolutionary history, since both basins are geographically close to each other. Finally, the present study shows that a multi-approach analysis is particularly useful in identifying the population structure of widely distributed species and to evaluate the impacts of human activities on natural fish populations.

In the present work, morphometric and cytogenetic analyses were carried out in populations of the fish Astyanax fasciatus (Characidae) from Contas and Recôncavo Sul River basins (State of Bahia, Brazil), providing new data on the genetic structure of this species along the region. Based on morphologic measurements, we observed that populations from the same hydrographic basin were more similar to each other (Contas and Preto do Costa Rivers), and remarkably divergent from Recôncavo Sul (Mineiro Stream), as indicated by clustering analysis. Cytogenetic data revealed a same diploid number for all populations (2n = 48), but distinct karyotype formulae (8M+24SM+12ST+4A, FN = 92 in Contas River, 8M+24SM+10ST+6A, FN = 90 in Preto do Costa River, and 8M+18SM+16ST+6A, FN = 90 in Mineiro Stream). Ag-NORs were identified at telomeres on a subtelocentric chromosome pair, although multiple ribosomal sites have been detected in some specimens from Contas River. These results show that A. fasciatus populations from northeastern river basins are well differentiated and present peculiar cytogenetic features when compared to populations from other regions. Therefore, the apparent chromosomal plasticity of this species, likely to represent a complex of cryptic forms, is corroborated. Finally, we demonstrated that morphological features can be successfully used to support other sources of genetic information.