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Search Results: 1 - 10 of 33090 matches for " Fausto;Oliveira "
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Cytotaxonomic diagnosis of Trichomycterus diabolus (Teleostei: Trichomycteridae) with comments about its evolutionary relationships with co-generic species
Torres, Rodrigo A.;Oliveira, Claudio;Foresti, Fausto;
Neotropical Ichthyology , 2004, DOI: 10.1590/S1679-62252004000300003
Abstract: the karyotype and the ag-nor location of a sample of trichomycterus diabolus collected in the córrego hortel? (botucatu, s?o paulo, brazil) are described. the species exhibited 2n=56 chromosomes (42 metacentrics, 12 submetacentrics and 2 subtelocentrics) and the nucleolus organizing region located near to the centromere on the long arm of the largest metacentric pair. the presence of 2n=56 chromosomes in t. diabolus is an interesting characteristic since until now all cis-andean species karyotyped presented 2n=54 chromosomes while almost all trans-andean species presented different diploid numbers. the possible origin of this unexpected karyotypic form is discussed.
Karyological characterization of four Neotropical fish species of the genus Hisonotus (Teleostei, Loricariidae, Hypoptopomatinae) from distinct Brazilian river basins
Andreata, Artur Antonio;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 2006, DOI: 10.1590/S1415-47572006000100013
Abstract: the karyotypes of four hisonotus species (two provisionally-named species a and d, h. nigricauda, and h. leucofrenatus) were found to have the same diploid number of 2n = 54 and interstitial silver-staining nucleolus organizer regions (ag-nors) located on the long arm of the largest metacentric pair. the c-banding pattern appeared to be species-specific, with one group (h. nigricauda and the unnamed species a and d) being characterized by small amounts of positive c-banded segments and containing a sub-group (species a and d) identified by a large positive c-banded segment on a small metacentric chromosome pair. the second group contained different samples of h. leucofrenatus, characterized by a larger amount of c-band positive segments spread over several chromosome arms. heterochromatin appears to play an important evolutionary role in chromosome differentiation in hisonotus species, especially in h. leucofrenatus. the geographic isolation of several h. leucofrenatus populations seems to have favored chromosome evolution of each sample analyzed.
Karyotype description of five species of Trichomycterus (Teleostei: Siluriformes: Trichomycteridae)
Sato, Luciana Ramos;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 2004, DOI: 10.1590/S1415-47572004000100008
Abstract: trichomycteridae is a family of small catfish which are widely distributed throughout southern central america and south america. the present study showed that the cis-andean species trichomycterus florensis, trichomycterus sp. aff. trichomycterus itatiyae, trichomycterus reinhardti, trichomycterus davisi and trichomycterus auroguttatus had 2n = 54 chromosomes (42 metacentric, 10 submetacentric and 2 subtelocentric), with t. reinhardti, t. auroguttatus and t. sp. aff. t. itatiyae exhibiting only one chromosome pair with silver-stained nucleolus organizer regions (nors). the cytogenetic data suggest the existence of at least two groups of species in the cis-andean representatives of the genus trichomycterus. in the first group the first metacentric pair is considerably larger than the second metacentric pair and the nors occur in the pericentromeric position of the short arm of a large submetacentric pair while in the second group the first and second metacentric pairs are about the same size and larger than the other metacentric pairs and the nors are located in the pericentromeric position of the long arm of a large metacentric pair. the relative conservatism of the karyotype of the cis-andean trichomycterus species contrasts with the wide diversification observed in the trans-andean species, reinforcing the hypothesis that the genus is not monophyletic.
R- and G-band patterns in Astyanax scabripinnis paranae (Pisces, Characiformes, Characidae)
Maistro, Edson Luis;Foresti, Fausto;Oliveira, Claudio;
Genetics and Molecular Biology , 1999, DOI: 10.1590/S1415-47571999000200011
Abstract: the absence of longitudinal bands in fish chromosomes has been associated with technical problems in chromosome preparations or the absence of a structural compartmentalization in the fish genome. in the present study, a r-banding pattern was obtained using a replication banding technique by in vivo treatment with 5-bromodeoxyuridine (5-brdu). g-banding patterns were obtained after trypsin treatment and also after chromosome cleavage by in situ treatment with the restriction endonuclease bamhi. a similar g-banding pattern was also obtained after cleavage with the endonuclease hinfi. presence of a resolute r- and g-banding patterns shows that astyanax scabripinnis paranae chromosomes could present an isochore-like structure similar to that found in other vertebrates.
Comparative cytogenetic and morphological analysis of Astyanax scabripinnis paranae (Pisces, Characidae, Tetragonopterinae)
Maistro, Edson Luis;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 1998, DOI: 10.1590/S1415-47571998000200005
Abstract: cytogenetic and morphological studies were carried out on nine local populations ofastyanax scabripinnis paranae. all populations exhibited 2n = 50 chromosomes as well as conspicuous differences involving karyotype morphology, number and position of nucleolar organizer regions (nors) and amount and/or locations of constitutive heterochromatin blocks. a quantitative study of the cytogenetic data showed that eight populations possessed different karyotypes. morphological analyses based on nine measurements and two meristic parameters were effective in establishing clear identification of five populations. comparative analysis of cytogenetic and morphological traits suggests that chromosomal changes have occurred at a more rapid rate than morphological differentiation. despite the close morphological similarity found among some populations, chromosomal differentiation was identified in all of them, even in those presenting only small morphological differences.
Nuclear DNA content of thirty species of Neotropical fishes
Carvalho, Margarida Lima;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 1998, DOI: 10.1590/S1415-47571998000100009
Abstract: the present paper reports nuclear dna content in 30 neotropical freshwater fish species and summarizes the data on other neotropical species presented in the literature. among neotropical fishes, the nuclear dna content ranges from 1.04 ± 0.09 pg/nucleus in corydoras cf. simulatus (2n = 62) to 248.0 pg/nucleus in lepidosiren paradoxa (2n = 38). a general analysis of the data obtained in the present study for each species showed that dna measurements were practically constant at the individual level, while significant differences were observed among individuals of the same population. this observation was valid for all species analyzed and was more evident in those species that presented other karyotypic particularities such as sex chromosomes or supernumerary chromosomes. the importance of changes in nuclear dna content in the evolutionary process of neotropical fishes is discussed.
Sympatric occurrence of two cytotypes of Astyanax scabripinnis (Characiformes, Characidae)
Maistro, Edson Luis;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 2000, DOI: 10.1590/S1415-47572000000200021
Abstract: among four specimens of astyanax scabripinnis sympatrically collected from the tamanduá stream (state of s?o paulo, brazil), three, named cytotype i, had 2n = 50 chromosomes (6m + 26sm + 4st + 14a) and a fundamental number (fn) of 86, and one specimen, named cytotype ii, had 2n = 48 chromosomes (6m + 28sm + 4st + 10a) and fn = 86. besides the difference in diploid number, the cytotypes showed a clear difference in the distribution of constitutive heterochromatin. one nor-bearing chromosome pair was detected in both cytotypes and one specimen of cytotype i had multiple nors (tree chromosome pairs). robertsonian translocations and an increase or loss of heterochromatin are proposed to explain the karyotypic divergence observed. some aspects related to the chromosome evolution of astyanax scabripinnis are discussed.
Description of a ZZ/ZW sex chromosome system in Thoracocharax cf. stellatus (Teleostei, Characiformes, Gasteropelecidae)
Carvalho, Margarida Lima;Oliveira, Claudio;Foresti, Fausto;
Genetics and Molecular Biology , 2002, DOI: 10.1590/S1415-47572002000300008
Abstract: the family gasteropelecidae is composed of three genera and eight species. this study shows that thoracocharax cf. stellatus has 2n = 52 chromosomes for both sexes. the five males studied showed 8 metacentric, 16 submetacentric, 4 subtelocentric, and 24 acrocentric chromosomes; the seven females showed only one submetacentric chromosome, belonging to pair 11, and one extra acrocentric chromosome, smaller than all the other chromosomes, characterizing the presence of a zz/zw sex chromosome system in this species. nucleolus organizing regions (nors) were detected on the short arms of the subtelocentric chromosome pair 13. constitutive heterochromatin was identified at pericentromeric and terminal positions in almost all chromosomes. the w chromosome was almost entirely heterochromatic, except for a small terminal euchromatic segment. the analyses of the amount of nuclear dna found 2.18 ± 0.09 pg of dna per diploid nucleus, without significant differences between sexes. a discussion about the evolution of the sex chromosomes in this group is presented.
Description of a ZZ/ZW sex chromosome system in Thoracocharax cf. stellatus (Teleostei, Characiformes, Gasteropelecidae)
Carvalho Margarida Lima,Oliveira Claudio,Foresti Fausto
Genetics and Molecular Biology , 2002,
Abstract: The family Gasteropelecidae is composed of three genera and eight species. This study shows that Thoracocharax cf. stellatus has 2n = 52 chromosomes for both sexes. The five males studied showed 8 metacentric, 16 submetacentric, 4 subtelocentric, and 24 acrocentric chromosomes; the seven females showed only one submetacentric chromosome, belonging to pair 11, and one extra acrocentric chromosome, smaller than all the other chromosomes, characterizing the presence of a ZZ/ZW sex chromosome system in this species. Nucleolus organizing regions (NORs) were detected on the short arms of the subtelocentric chromosome pair 13. Constitutive heterochromatin was identified at pericentromeric and terminal positions in almost all chromosomes. The W chromosome was almost entirely heterochromatic, except for a small terminal euchromatic segment. The analyses of the amount of nuclear DNA found 2.18 ± 0.09 pg of DNA per diploid nucleus, without significant differences between sexes. A discussion about the evolution of the sex chromosomes in this group is presented.
Karyotype description of five species of Trichomycterus (Teleostei: Siluriformes: Trichomycteridae)
Sato Luciana Ramos,Oliveira Claudio,Foresti Fausto
Genetics and Molecular Biology , 2004,
Abstract: Trichomycteridae is a family of small catfish which are widely distributed throughout Southern Central America and South America. The present study showed that the cis-Andean species Trichomycterus florensis, Trichomycterus sp. aff. Trichomycterus itatiyae, Trichomycterus reinhardti, Trichomycterus davisi and Trichomycterus auroguttatus had 2n = 54 chromosomes (42 metacentric, 10 submetacentric and 2 subtelocentric), with T. reinhardti, T. auroguttatus and T. sp. aff. T. itatiyae exhibiting only one chromosome pair with silver-stained nucleolus organizer regions (NORs). The cytogenetic data suggest the existence of at least two groups of species in the cis-Andean representatives of the genus Trichomycterus. In the first group the first metacentric pair is considerably larger than the second metacentric pair and the NORs occur in the pericentromeric position of the short arm of a large submetacentric pair while in the second group the first and second metacentric pairs are about the same size and larger than the other metacentric pairs and the NORs are located in the pericentromeric position of the long arm of a large metacentric pair. The relative conservatism of the karyotype of the cis-Andean Trichomycterus species contrasts with the wide diversification observed in the trans-Andean species, reinforcing the hypothesis that the genus is not monophyletic.
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