Journal ArticleDOI
Cytogenetic Considerations on the Genus Astyanax (Pisces, Characidae). I. Karyotypic Variability
TLDR
In this paper, a study was carried out on mitotic and meiotic chromosomes of four species of the genus Astyanax from three different water basins in the State of Sao Paulo, Brazil.Abstract:
SUMMARYA study was carried out on mitotic and meiotic chromosomes of four species of the genus Astyanax (Pisces, Characidae) from three different water basins in the State of Sao Paulo, Brazil. The following karyotypic characteristics were observed: A. bimaculatus, 2n = 50 (n = 25, FN = 86–88); A. fasciatus, 2n = 46 (n = 23, FN = 90); « A. fasciatus » from the Juquia river, 2n = 48 (n = 24, FN = 94); A. schubarti, 2n = 36 (n = 18, FN = 70) and A. scabripinnis paranae, 2n = 50 (n = 25, FN = 90–92). The diversity in the number and morphology of the chromosomes suggests a model of non-conservative karyotypic evolution in this genus, with chromosome rearrangements of the centric fusion/fission type and/or inversion playing an important role in these alterations. On the basis of its characteristics, A. schubarti has the most differentiated karyotype and, in view of the low diploid number and small number of subtelocentric-acrocentric chromosomes, is probably of most recent origin. The two karyotypes encountere...read more
Citations
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Journal ArticleDOI
Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental influences
TL;DR: The lability of sex-determination systems in fish makes some species sensitive to environmental pollutants capable of mimicking or disrupting sex hormone actions, and such observations provide important insight into potential impacts from endocrine disruptors, and can provide useful monitoring tools for impacts on aquatic environments.
Journal ArticleDOI
Accentuated polymorphism of heterochromatin and nucleolar organizer regions in Astyanax scabripinnis (Pisces, Characidae): tools for understanding karyotypic evolution.
Monique Mantovani,Luciano Douglas dos Santos Abel,Carlos Alberto Mestriner,Orlando Moreira-Filho +3 more
TL;DR: The mechanisms involved in the dispersion of heterochromatin and NORs through the karyotypes, as well as the possible events related to the generation of polymorphism of those regions are discussed.
Journal ArticleDOI
Genetics of neotropical fish: from chromosomes to populations.
TL;DR: A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution.
Journal ArticleDOI
Food partitioning among some characids of a small Brazilian floodplain lake from the Paraná River basin
TL;DR: Acute cyclic changes in the environment, as observed in this study, suggest the necessity of small interval sampling in food partitioning studies in tropical freshwater floodplains, in order to understand how species interact and cope with changes in food availability.
Journal ArticleDOI
B chromosomes in Astyanax scabripinnis (Pisces, Characidae)
TL;DR: Two types of B could be identified on the basis of their constitutive heterochromatin patterns, similar in size and shape to pair 1 of the karyotype, with a high intra-individual constancy.
References
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Journal ArticleDOI
Nomenclature for centromeric position on chromosomes
TL;DR: At the present time, with the immense increase in research activity in mammalian cytology, the terminology of the centromeric position has become burdened by much obscurity and confusion.
Journal ArticleDOI
Rapid Chromosome Preparations from Solid Tissues of Fishes
TL;DR: A technique is described for obtaining well-spread metaphases from solid tissues of fishes without the use of methodologies that rely on tissue grinders, centrifuges, digestive enzymes, or tissue culture.
Book ChapterDOI
Chromosomes of Two Fish-Species of the Genus Diretmus (Osteichthyes, Beryciformes: Diretmidae)
TL;DR: In addition to an ichthyological program cytological studies were carried out during the 36th cruise of the FRS “Walther Herwig” during which smear preparations of gonads dissected from adult males of 47 species of oceanic fishes furnished the material for investigations.