Search

Molecular markers can be used to monitor genetic variability in cultivated fish stocks with the aim of developing better aquaculture techniques and increasing productivity. In view of the above, the objective of the present work was to evaluate the genetic variability in pirarucu broodstocks in fish farms in the southeast and northeast of the of Pará state, Brazil. The samples were genotyped using four microsatellite markers, and genetic diversity indices were calculated for each broodstock. A total of 16 alleles were identified from the four loci tested in the 33 pirarucu samples, with means of 3.00, 2.75, and 2.25 alleles per locus in broodstocks from Tucumã, Parauapebas, and Moju municipalities, respectively. The Parauapebas broodstock had the highest mean observed heterozygosity. In the broodstocks from Tucumã and Parauapebas, the markers AgCAm16 and AgCAm18 were not at Hardy-Weinberg equilibrium. This pilot study showed that there were considerable losses of genetic variability in pirarucu breeding centers in the municipalities of Tucumã, Parauapebas and Moju compared to the variability in the natural populations of this fish species. [ABSTRACT FROM AUTHOR]

Leporinus friderici is a migratory neotropical fish with elevated ecological and economic importance in Brazil. Microsatellite markers are highly important in population genetic studies, management, and conservation programs; however, no markers are available for this species. In this study, seven microsatellite loci, previously developed for Megaleporinus obtusidens, were successfully cross-amplified in L. friderici. Among these loci, five presented moderate to high genetic variability levels, with four to seven alleles per loci and expected heterozygosities varying from = 0.574 to 1.000. These markers represent a valuable tool for the future management and ecological studies involving this species and group of neotropical fishes. [ABSTRACT FROM AUTHOR]

The chromosomal location of 5S rRNA and U2 snRNA genes of Piabina argentea, Piabarchus stramineus and two Bryconamericus species from two different Brazilian river basins were investigated, in order to contribute to the understanding of evolutionary characteristics of these repetitive DNAs in the subfamily Stevardiinae. The diploid chromosome number was 2n = 52 for Bryconamericus cf. iheringii, Bryconamericus turiuba, Piabarchus stramineus and Piabina argentea. The 5S rDNA clusters were located on one chromosome pair in P. stramineus and B. cf. iheringii, and on two pairs in B. turiuba and P. argentea. The U2 snDNA clusters were located on the one pair in all species. Two-color FISH experiments showed that the co-localization between 5S rDNA and U2 snDNA in P. stramineus can represent a marker for this species. Thus, the present study demonstrated that the number of U2 snDNA clusters observed for the four species was conserved, but particular characteristics can be found in the genome of each species. [ABSTRACT FROM AUTHOR]

The present study sought to identify general patterns of genetic variability and structure of fish stocks (migratory and non-migratory species) along one of the largest Brazilian rivers, the São Francisco. Given that genetic variability of populations of all organisms is governed by both present and past influences, herein we investigate both these aspects by evaluating the current genetic differences between populations of five species ( Leporinus piau, Megaleporinus reinhardti, Pimelodus maculatus, Prochilodus argenteus, and Pygocentrus piraya) along the entire extension of the river, as well as their demographic history. Analyses were done through sequences of two mitochondrial fragments and microsatellite data. In general, the data showed no support for recent fragmentation of stocks by the dams present in this river, and that all species show signs of past population expansion. We discuss the possible reasons for the common patterns found between these species, including the influence of the river's topography and history. [ABSTRACT FROM AUTHOR]

Individuals of jacks that were captured off the Rio de Janeiro coast were characterized using multivariate morphometrics and allozymes molecular markers. The main objectives were to determine the number of fish captured and their species. Classical taxonomic classification and multivariate morphometry indicated the existence of three species in the landings from Rio de Janeiro State ( Caranx crysos , Carangoides bartholomaei and Caranx latus ). The results of the genetic analyses performed were consistent with these results. However, Bayesian analysis revealed the possible presence of a fourth species, which could not be discriminated by classical taxonomy. Caranx crysos possibly comprises two different species. Other population indexes, such as unique alleles, degree of structuring and genetic identity, also pointed to different species. Therefore, based on evidences from classical taxonomy, geometric morphometric analyses together with genetic data from allozymes molecular markers it is possible to support that at least four different Carangidae species are present in fish landings from Niterói, Rio de Janeiro State, Brazil, whereas fish capture records for the same location have recorded only two species. These results are important for not only developing fisheries management strategies but also providing general information regarding the ecology and evolution of the genus. [ABSTRACT FROM AUTHOR]

Oysters of the genusCrassostreaare an economically important resource occurring along the Brazilian coast, mainly in estuarine regions. Inter- and intra-population genetic diversity is essential for monitoring long-term genetic changes and for sustainable use of this bivalve by coastal fishing communities. Microsatellite markers were used to evaluate the genetic diversity of natural populations of the mangrove oysterCrassostrea rhizophoraein southeastern Brazil. Samples of 150 oysters from four areas were analyzed. Microsatellite loci were obtained from an enriched microsatellite library. The genetic structure was evaluated using an index of genetic differentiation described previously. The effective population size and rate of gene flow were estimated through a maximum likelihood coalescent approach using Migrate. The mean number of alleles ranged from 10 to 21 and the expected heterozygosity from 0.89 to 0.91. Evidence of a possible bottleneck effect under three mutational models was found. TheDestindex indicated low to moderate differentiation among sample locales. Coalescent analysis showed variation in effective population size and asymmetry in the gene flow among samples. Levels of genetic variability and differentiation found amongC. rhizophoraepopulated banks have important implications for the sustainable harvest, cultivation and conservation of this marine resource in the studied area. [ABSTRACT FROM PUBLISHER]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fish have been shown to act as sentinel organisms in genetic toxicology studies and the micronucleus (MN) test using fish erythrocytes has been successfully used to evaluate the genotoxic impact of environmental pollutants on aquatic environments. This study used the MN test of peripheral blood of specimens of a native fish species (Hyphessobrycon luetkenii) to evaluate the genotoxicity of the water of two unconnected reservoirs of the Canela National Forest in southern Brazil. Fish were caught in the reservoirs and MN frequencies in blood smears were determined. Baseline MN frequency ofH. luetkeniiwas determined in the uncontaminated reservoir (reference site) and compared with the results obtained at two different sampling periods (winter and spring) in the reservoir which receives discharges of industrial and municipal wastes. In the spring season, MN frequency in the contaminated reservoir was about five times higher than in the reference site (0.51‰ and 0.10‰, respectively). The results of this study indicate that some fish populations are at risk of exposure to genotoxic pollutants in the Canela National Forest. [ABSTRACT FROM AUTHOR]

Abstract: Historically, the ichthyofauna of large Brazilian rivers has been subject to anthropogenic interference, such as impoundments. Currently, cage fish farming systems are a new source of impact on aquatic ecosystems. The objective of this study was to characterise the impact of freshwater fish farms on the feeding of five species of Neotropical freshwater fish. Specimens of Astyanax altiparanae, Galeocharax knerii, Iheringicthys labrosus, Pimelodus maculatus and Plagioscion squamosissimus were sampled in areas around two systems of cage fish farming (CF), and two control areas (CT) that were not influenced by this activity. Results show that there were significant changes in the diet of trophic generalist species (A. altiparanae, P. maculatus and I. labrosus) accompanied by a related increase in the condition factor values of these species in cage areas. Trophic specialist species, such as the carnivorous fish species G. knerii and P. squamosissimus, presented small differences between the CF and CT areas with regard to diet and showed no differences in other analyses performed. In conclusion, cage fish farms can affect the natural diet of trophic generalist fish species, directly affecting the nutritional status (condition factor), where food wastes was found to be one of the principal items consumed by this trophic guild. Results indicate that these species are responsible for recycling a great quantity of organic matter transferred by this type of activity, which, along with local fishery activities, contribute to mitigation of associated processes of eutrophication. [Copyright &y& Elsevier]

Abstract: We provide initial information regarding the population structure and genetic diversity of Stenella frontalis from the Caribbean and southeastern Brazil from analyses of mitochondrial control region sequences and sequences from the first intron of the α-lactalbumin gene. Comparisons with previously described S. frontalis sequences showed a high number of haplotypes shared between populations throughout their distribution range. High diversity was found for southeastern Brazil and Caribbean samples, and population structure analyses indicate significant differentiation among population units at the F ST level, but not at the Φ ST level. Significant differentiation at the F ST level was found between the Caribbean population unit and all other populations units. These results suggest historical or present connectivity between the Azores and Madeira and the southeastern Brazil groups and population differentiation between the Caribbean and southeastern Brazil, supporting the notion of two separate stocks in the waters around the Atlantic coast of South America. [Copyright &y& Elsevier]

Abstract: Molecular markers (Multiplex-PCR and PCR-RFLP of nuclear and mitochondrial genes) were used to assess the frequency of hybrids in wild stocks of two catfish species: Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum. Analysis of fish from the Paraguay–Parana hydrographic basin (Brazil) revealed a low frequency of hybrids in the Parana River (3.60%), which might be the result of natural hybridisation. However, the frequency of hybrids was higher in the Mogi Guaçu (50.00%) and Aquidauana (30.75%) Rivers, whose aquaculture systems support the majority of Brazil''s fish farms, suggesting that the existence of hybrids in wild populations may be due to introduction or escapes from farm stocks. Furthermore, the identification of a post-F1 individual in the Mogi-Guaçu River provides evidence of genetic introgression. These results show that safeguards are needed to ensure the correct handling of hybrids and the protection of native species. [Copyright &y& Elsevier]

Biological monitoring through animals exposed to pollutants using biomarkers provides a promising tool for the identification of pollutants that may cause damage to human health and/or to sustainability of ecosystems. The effects of pollutants in fish tissues are important tools to understand the impact of human activities in natural ecosystems. The aim of this work was to study the water quality of two estuarine lakes in Santa Catarina, Brazil (Camacho Lake and Santa Marta Lake). Geophagus brasiliensis is a species widely distributed in Brazil and was used in this work. Comet assays in peripheral red blood and kidney cells, micronucleus tests in peripheral red blood cells, measurements of acetylcholinesterase activity in axial muscle and histopathological analysis of liver were used as biomarkers. Three sampling campaigns were undertaken in November 2004, June 2005 and November 2005. Thirty adult animals were sampled from each of three different sites (P1-Santa Marta Lake, P2 and P3-Camacho Lake). A negative control was sampled in a non-polluted site at Costa Ecological Park, Paraná. The positive control for genotoxicity was obtained by treating animals with copper sulphate. The results showed that both studied lakes are impacted by potential genotoxic substances. Severe lesions in liver of G. brasiliensis were also observed. The inhibition of acetylcholinesterase activity suggests the presence of pesticides or metals in the studied sites. This work shows that the water quality of Santa Marta and Camacho Lakes have been compromised and further control source of pollutants into these ecosystems is required. [ABSTRACT FROM AUTHOR]

This study documents unexpectedly low levels of intra and interpopulation genetic diversity in Kryptolebias ocellatus, an androdioecious and predominantly self-fertilizing killifish from south-eastern Brazil. This finding generally is inconsistent with the established opinion that the K. ocellatus and K. marmoratus clade originated in this geographic region and later dispersed northward into the Caribbean. [ABSTRACT FROM AUTHOR]

Abstract: Octopus vulgaris is a cephalopod species in several oceans and commonly caught by artisanal and industrial fisheries. In Brazil, O. vulgaris populations are mainly distributed along the southern coast and have been subjected to intensive fishing during recent years. Despite the importance of this marine resource, no genetic study has been carried out to examine genetic differences among populations along the coast of Brazil. In this study, 343 individuals collected by commercial vessels were genotyped at six microsatellite loci to investigate the genetic differences in O. vulgaris populations along the southern coast of Brazil. Genetic structure and levels of differentiation among sampling sites were estimated via a genotype assignment test and F-statistics. Our results indicate that the O. vulgaris stock consists of four genetic populations with an overall significant analogous F ST (ΦCT =0.10710, P <0.05) value. The genetic diversity was high with an observed heterozygosity of Ho=0.987. The negative values of FIS found for most of the loci examined suggested a possible bottleneck process. These findings are important for further steps toward more sustainable octopus fisheries, so that this marine resource can be preserved for long-term utilization. [Copyright &y& Elsevier]

The freshwater silver catfish from the genus Rhamdia belongs to a group of neotropical fish with wide distribution throughout Central and South America. The results obtained in the F1 generation of native specimens of this species bred in captivity using molecular cytogenetic tools revealed a high number of triploid specimens (46.8%) in the samples analyzed. The use of double fluorescent in situ hybridization (double-FISH) with 18S and 5S rDNA probes allowed highlighting the location of ribosomal sites with independent activity. This chromosome marker allowed the identification of triploid nuclei, in which three markers were visualized, in contrast to diploid fish, which only exhibited two fluorescent signals. As triploid specimens exhibit either total or partial gonad sterility, the present study demonstrates the importance of cytogenetic monitoring in restocking programs aimed at genetic conservation. [ABSTRACT FROM AUTHOR]

Abstract: We investigated demographic history and population structuring of Colossoma macropomum sampled from 14 localities in the Amazon basin and the Bolivian sub-basin; the two basins are separated by a series of 16 rapids. Although genetically differentiated, IMa analyses suggest non-zero bi-directional migration rates, and inter-basin divergence of approximately 17 thousand years ago. Analyses in BEAST indicated that Bolivian C. macropomum has been demographically stable except for a moderate population increase in the last 12 thousand years, while Amazonian C. macropomum has been experiencing demographic growth over the last 350 thousand years, resulting in approximately one order of magnitude increase in coalescent Ne . [Copyright &y& Elsevier]

Characidium fishes with a sex chromosome system form a monophyletic group. This work presents data of Characidium lanei from the South Atlantic basin (Brazil), including an unknown type of ZW sex chromosome system for the groups including the presence of rDNA sites on sex chromosomes. [ABSTRACT FROM AUTHOR]

The aim of the present study is to test by molecular DNA data a hypothesis concerned to speciation by allopatry occurring in Mimagoniates microlepis, associated to the Serra do Mar mountain chain (Atlantic Rain Forest hotspot) in Southern Brazil. Overall genetic diversity and mean genetic distances were high, demonstrating both good conservation status and genetic differentiation. Neighbor-Joining (NJ) and parsimony analyses, together with population genetic parameters (ΦST, Nm, GST, and AMOVA), identified two main vicariant genetic/evolutionary stocks dividing the upper Iguaçu River samples from those of the coastal plains. Other well-supported intrinsic monophyletic clades were also identified, suggesting fast and remarkable speciation processes. In addition, the genetic, evolutionary, geographic, and phylogeographic evidences reinforced an occurring species complex. Moreover, these evolutionarily significant units (species complex) seem to be inside four natural biogeographic areas. Thus, the genesis and evolution of the Serra do Mar complex might be associated to diversification processes of M. microlepis. Such a consideration suggests that the areas including the upper Iguaçu River and the coastal plains of the states of São Paulo, Paraná, and Santa Catarina require distinct conservation policies involving one of the global biodiversity hotspots, namely, the Brazilian Atlantic Rain Forest. [ABSTRACT FROM AUTHOR]

The taxonomy of the genus Hypostomus in the upper Rio Paraná basin presents some very complex issues. For this reason, an allozyme electrophoresis survey of 10 populations of Hypostomus from the Rio Corumbá basin was performed, revealing 25 loci from 14 enzyme systems. Allozyme data revealed diagnostic genetic markers for the four nominal species analyzed ( Hypostomus ancistroides, H. iheringi, H. margaritifer, and H. regani) and for six possible undescribed species. The mean expected heterozygosity of the populations ranged from 0.009 in H. iheringi to 0.099 in Hypostomus sp. 4. The genetically most similar populations ( I = 0.954) were H. iheringi and Hypostomus sp. 2; the most divergent ( D = 0.839) were H. iheringi and H. ancistroides. [ABSTRACT FROM AUTHOR]

Cytogenetic analyses were performed on three Gymnotus species, Gymnotus paraguensis, Gymnotus sylvius and Gymnotus pantanal, collected in sympatry in the region of Guaíra, Paraná State (Brazil). Gymnotus paraguensis presented 54 chromosomes (52m-sm + 2st) in both sexes, G. sylvius presented 40 chromosomes (36m-sm + 4a) in both sexes and G. pantanal presented 40 chromosomes (14m-sm + 26a) in females and 39 (15m-sm + 24a) in males, with an X1X1X2X2/X1X2Y multiple sex chromosome system. All three species had single nucleolar organizing regions and heterochromatin in the centromeric region of most chromosomes. Gymnotus pantanal, previously collected only in the Lower Paraná and Paraguay River basins, was confirmed for the first time in the Upper Paraná River basin. This species constitutes one of several examples of species that have colonized the region after flooding of the great Sete Quedas waterfalls by the construction of the Itaipu hydroelectric dam. The probable absence or infertility of hybrids is indicated by the high level of chromosome differentiation between these species. [ABSTRACT FROM AUTHOR]

Abstract  Morphometric analyses of 220 specimens of a characid, Bryconops sp. cf. melanurus, from the Brazilian Pantanal were used to describe allometric growth in that species and determine whether specimens from highland habitats were more streamlined than those from lowland habitats. Relative warp analysis of 14 landmarks and principal component analysis of 28 interlandmark distances returned complementary results. The increased streamlining of the highland specimens is highly consistent with known inductive effects of high water velocity on fish phenotypes. Genetic differentiation and inductive effects of temperature variation are also potential explanations of the observed phenotypic differentiation. [ABSTRACT FROM AUTHOR]

Brycon species are the most important local fishing source, wherever found, and therefore, are seen as having great economical value. Based on the amplification of genomic DNA by PCR (Polymerase Chain Reaction) with arbitrary nucleotide sequence primers, RAPD can detect high levels of DNA polymorphisms and can produce fine genetic markers. Nowadays, the main concern of researchers and scientific studies, regarding genetics and improvement of fish lineage in Brazil, has been directed to the organization and characterization of genetic banks to study native populations. In order to contribute to restock programs and deeply understand the framework of the piracanjuba Brycon orbignyanus the genetic divergence and variability of these stocked populations were estimated by using the RAPD markers. The population of piracanjuba reproducers from Castilho (São Paulo - Brazil) and Porto Ferreira (São Paulo - Brazil) and their offspring were evaluated. Jaccard's similarity coefficient matrix was used in order to elaborate a dendrogram, and the genetic divergence among populations was determined by Mantel's test. The genetic variability was estimated by using both Shannon's index and the polyphormic loci percentage. The genetic divergence in Castilho'$s population (0.1551) and its offspring (0.1889) and the genetic variability (Shannon's index: 0.3184 in Castilho's population and 0.3433 in offspring; polyphormic loci percentage: 54.02% and 57.47% respectively) were similar, indicating that the control of non-intentional selection was efficient in maintaining reproducers genetic diversity. Porto Ferreira's population showed similar values of genetic divergence (0.1987 and 0.1970) and variability (Shannon's index: 0.3687; polyphormic loci percentage: 58.62%) to Castilho's population and its offspring respectively, therefore, the values of genetic divergence and genetic variability remained uniform, which means that, basically, there was no populations or progeny genetic changes, despite being geographically separated one from the other. [ABSTRACT FROM AUTHOR]