New occurrence of microchromosomes B in Moenkhausia sanctaefilomenae (Pisces, Characidae) from the Parana River of Brazil: analysis of the synaptonemal complex

The Moenkhausia sanctaefilomenae specimens showed a karyotype consisting of 2n = 50 chromosomes with 12 metacentrics, 36 submetacentrics and two subtelocentrics. In addition to the basic karyotype, all the males specimens have cells ranging from zero to two B microchromosomes in mitotic metaphases. These chromosomes were not observed in the female specimens. C-band analysis showed a distribution pattern of characteristic heterochromatin with interstitial and centromeric blocks. However, the B chromosomes were faintly stained with C-banding and were not fluorescent with CMA(3) staining. The meiotic studies showed the formation of bivalents in metaphase I and in pachytene under an optical microscope. Through synaptonemal complex analysis with an electron microscope, the pachytene showed 25 bivalents completely paired and a small bivalent corresponding to the B chromosomes. In the same preparation, one of the B chromosomes was observed in a univalent form. on the basis of pairing behavior and morphology it is assumed that B chromosomes of M. sanctaefilomenae show homology between them and their evolutionary aspects are discussed.

Cytogenetical analyses in three Astyanax scabripinnis populations (Pisces, Characidae) from Minas Gerais State, Brazil

Cytogenetical data in 3 populations of characid fish assigned to the complex of Astyanax scabripinnis from São Francisco river basin and Grande river basin, Minas Gerais State, Brazil, are presented for the first time. The same diploid number, 2n=50, was detected in the 3 populations, which has conspicuous differences involving karyotype morphology: 8M, 20SM, 6ST and 16A (Cambeba stream), 6M, 28SM, 6ST and 10A (Machado headwater), 6M, 24SM, 8ST and 12A (Pedra Branca stream). Differences involving amount and/or locations of heterochromatin blocks, number and position of nucleolar organizer regions (NORs) and CMA3 positive signals were also observed. Some aspects related to the chromosome diversification of Astyanax scabripinnis are discussed. © 2007 The Japan Mendel Society.

Influência de uma piscicultura em tanquesrede na dieta e atributos biológicos de Galeocharax knerii na represa de Chavantes, Brasil

The aim of the present study was to evaluate the diet and biological attributes of the population of Galeocharax knerii residing near net cage fish farming activities in the Chavantes reservoir (Paranapanema River, Brazil) to check their possible impacts. Samples were collected from two populations: one near the net cages (NC) and one from an area not influenced by these cages denominated the reference site (RS). Monthly sampling was carried out from March 2008 to February 2009. Fish were caught with a standardized effort using gill nets deployed for 14 hours. The alimentary index (AI) and degree of repletion (RD) were calculated to determine diet composition. Analyses of the sex ratio and the gonadosomatic index (GSI) were also performed. The calculations of AI revealed that fish wastes constituted the most frequent food item in the diet in both study areas (NC = 70.43; RS = 87.55), followed by the consumption of Apareiodon affinis (AI = 29.56), which was abundant near the NC, and prawn at the reference site (AI = 12.28). The sex ratio differed from 1:1 and mature individuals were only found in the population near the NC. The findings demonstrate that G. knerii indirectly benefits from the input of organic matter, using small fish as its main food resource. We conclude that the activities of fish farming influence diet and biological attributes of the species G. knerii, evidenced mainly by higher feeding activity, numerical abundance and biomass in the area of the cages.

Brycon gouldingi (Teleostei, Characidae): aspects of the embryonic development in a new fish species with aquaculture potential

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Screening and characterization of sex-specific DNA fragments in the freshwater fish matrinch, Brycon amazonicus (Teleostei: Characiformes: Characidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

DNA barcoding reveals hidden diversity in the Neotropical freshwater fish Piabina argentea (Characiformes: Characidae) from the Upper Parana Basin of Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Three sympatric karyomorphs in the fish Astyanax fasciatus (Teleostei, Characidae) do not seem to hybridize in natural populations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic structure of the ornamental tetra fish species Piabucus melanostomus Holmberg, 1891 (CHARACIDAE, IGUANODECTINAE) in the Brazilian Pantanal wetlands inferred by mitochondrial DNA sequences

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic characterisation of the ornamental freshwater fish, Piabucus melanostomus (Iguanodectinae) from Brazilian wetlands and its relation with species of Characidae basal group

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The role of riverine forests for food supply for the omnivorous fish Brycon opalinus Cuvier, 1819 (Characidae) in the Serra do Mar, Southeast Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hyphessobrycon rutiliflavidus n. sp., a new characid fish from the upper rio Paraguai, State of Mato Grosso, Brazil (Characiformes : Characidae)

Hyphessobrycon rutiliflavidus, new species, is described from the upper rio Paraguai in Cuiaba, State of Mato Grosso, Brazil. The new species differs from all other congeners by the following combination of characters: black humeral spot, slightly diffuse at its tips, and caudal-peduncle blotch present; midlateral body stripe conspicuous in its posteriormost portion, extending to the tips of the middle caudal rays; anal fin with iii, 15 to iv, 19 rays (mode iv, 17); upper jaw length, 42.3 to 49.5% of the head length; maxilla with 2-5 teeth (mode 3); all the fins of males reddish-orange and of females yellowish.

Extensive polymorphism and chromosomal characteristics of ribosomal DNA in the characid fish Triportheus venezuelensis (Characiformes, Characidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphofunctional changes in Leydig cells throughout the continuous spermatogenesis of the freshwater teleost fish, Serrasalmus spilopleura (Characiformes, Characidae): an ultrastructural and enzyme study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Frugivory by the fish Brycon hilarii (Characidae) in western Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morphological, cytochemical, and ultrastructural study of thrombocytes and leukocytes in neotropical fish, Brycon orbignyanus Valenciennes, 1850 (Characidae, Bryconinae)

Morphological, cytochemical and ultrastructural studies are important to demonstrate the function of the blood cells, which is very little understood in teleosts. In peripheral blood of piracanjuba' Brycon orbignyanus, thrombocytes, lymphocytes, monocytes, neutrophils and heterophils were studied and characterized. Thrombocytes had a fusiform or oval shape with PAS-positive granules. Lymphocytes presented small size with sparse basophilic cytoplasm. Monocytes were large in size, presented basophilic cytoplasm that may be foamy or vacuolated, with non-specific esterase staining. The neutrophils presented lightly neutrophilic granule cytoplasm, with positivity for PAS and peroxidase. The heterophils were large in size, with eosinophilic and basophilic granules cytoplasm and PAS-positive. Transmission electron microscopy study demonstrated that the thrombocytes, lymphocytes and monocytes features were similar to other teleosts. In ultrastructural study only one type of neutrophils was observed. Cytochemical findings indicated that neutrophils and monocytes of B. orbignyanus may be involved in phagocytosis, and neutrophils play an important microbicidal role.