Comparative Cytogenetics and Molecular Phylogeography in the Group Astyanax altiparanae - Astyanax aff. bimaculatus (Teleostei, Characidae)

The genus Astyanax comprises small characin fish of the neotropical region. The so-called `yellow-tailed characins` compose one of the most widely distributed Astyanax groups. A. altiparanae and A. aff. bimaculatus, are evolutionarily closely related and commonly found in several Brazilian hydrographic basins. In the present work, chromosomal data of specimens of A. altiparanae and A. aff. bimaculatus from 4 hydrographic basins in the states of Sao Paulo (Upper Tiete, Paranapanema, Ribeira de Iguape) and Rio de Janeiro (Guapimirim) are shown. All the populations showed 50 chromosomes, with different karyotypic formula. Although only a single Ag-NOR bearing chromosome pair was observed, all populations possess multiple cistrons of 18S rDNA. FISH with the 5S rDNA probe showed single signals at the interstitial position of one metacentric chromosome pair. C-bands are distributed in the terminal and interstitial regions of several chromosomes. However, the As-51 satDNA are frugally located in a few chromosomes of fishes from Upper Tiete, Paranapanema and Guapimirim Rivers, being absent in individuals of A. aff. bimaculatus from Ribeira de Iguape River basin. Beside these 4 populations, molecular phylogeography studies were also performed in individuals from Middle and Lower Tiete River basin and from 2 additional collection sites in the Paranapanema and Ribeira de Iguape River basins. The phylogeographic analysis using 2 mtDNA regions (totalizing 1.314 bp of ND2 and ATPase6/8 genes) of 8 populations of the group of `yellow-tailed characins` from 3 major hydrographic basins showed structuring of populations, suggesting a correlation between chromosomal (nuclear) and molecular (mitochondrial) data. Copyright (C) 2011 S. Karger AG, Basel

Redescription of Astyanax goyacensis Eigenmann, 1908 (Ostariophysi: Characiformes: Characidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Revalidação de Astyanax rupununi Fowler, 1914 (Teleostei, Characidae) e descrição de duas espécies novas para o gênero

A. rupununi Fowler, 1914, considerada sinônimo de A. bimaculatus (Linnaeus) por Eigenmann (1921) é revalidada e duas espécies novas são descritas: A. clavitaeniatus, do alto rio Branco, Roraima, Brasil, e A. siapae, da bacia do Casiquiare-Orinoco, Estados Amazonas e Apure, Venezuela. Essas três espécies apresentam o mesmo padrão básico de coloração: mancha umeral negra horizontalmente ovalada, mancha negra no pedúnculo caudal estendida à extremidade dos raios caudais medianos, duas barras verticais marrons (a primeira cruzando a mancha umeral e a segunda situada 23 escamas atrás) e característica faixa lateral negra em forma de clava. Os caracteres que distinguem as três espécies são discutidos e é apresentada uma chave de identificação para as três espécies.

Reprodução de peixes (Osteichthyes) em afluentes do reservatório de Volta Grande, Rio Grande, Sudeste do Brasil

The most abundant species caught in the tributaries of the Volta Grande dam, Buriti, Divisa and Água Comprida streams were Plagioscion squamosissimus (Heckel, 1840), Pimelodus maculatus Lacépède 1803, Myleus tiete (Eigenmann & Norris, 1900), Astyanax bimaculatus (Linnaeus, 1758) and A. fasciatus (Cuvier, 1819). Plagioscion squamosissimus and Pimelodus maculatus do not have reproduction activity in the area, they just use the creeks to food and growth. Myleus tiete and Astyanax bimaculatus use the area to reproduction whereas A. fasciatus uses it to reproduction, food and growth.

Redescription of Prosthenhystera obesa (Diesing, 1850) (Callodistomidae, Digenea) with New Host Records and Data on Morphological Variability

Prosthenhystera obesa (Diesing,1850) Travassos, 1922 from the gall bladder of Astyanax bimaculatus, Caranx gibbosus, Galeocharax humeralis, Leporinus copelandii, Pimelodus fur, Pseudopimelodus roosevelti, Salminus brevidens, Salminus maxillosus and from the new hosts, Cynopotamus amazonum and Triurobrycon lundii is redescribed, demonstrating a large morphological variation, mainly in body and testes size and shape. New hosts harbouring immature specimens of P. obesa are presented: Brycon sp., Leporellus vittatus, Pachyurus squamipinnis, Pimelodus clarias, Pseudoplatystoma corruscans and Salminus hilarii. Scanning electron microscopy micrographies, original figures and measurements of adult and immature specimens from different Brazilian hosts and localities are presented

Plasma levels of luteinizing hormone and gonadal maturation of lambari females under different photoperiods

The objective of this work was to evaluate the effect of photoperiod on luteinizing hormone (LH) plasma levels and gonadal maturation of lambari females. One hundred and twenty adult lambaris, distributed into 12 aquaria of 20 L each, were randomly subjected to three different treatments, in a completely randomized design, and four replicates. Treatments were photoperiods in hours of light (L) and darkness (D): T1, 0 L:24 D; T2, 12 L:12 D; T3, 24 L:0 D. After 40 days, fish were subjected to fasting for 24 hours and, then, anesthetized. Immediately after slaughter, fish were weighed, and their gonads and livers were removed and weighed. Ovaries were weighed and immersed in Bouin's fixative solution for 24 hours and, then, kept in 70% alcohol until processing the material. Subsequently, the oocyte developmental stage was determined. No significant differences were observed between treatments for final weight, ovary weight, gonadosomatic index (GSI), hepatosomatic index (HSI) and LH levels. In all treatments, lambari females showed maturing ovaries with prevalence of vitellogenic oocytes. Photoperiod does not affect the LH levels and ovarian maturation in lambari females.

Deep barcode divergence in Brazilian freshwater fishes: the case of the Sao Francisco River basin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

DNA barcodes discriminate freshwater fishes from the Paraiba do Sul River Basin, São Paulo, Brazil

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

Reprodução de peixes (Osteichthyes) em afluentes do reservatório de Volta Grande, Rio Grande, Sudeste do Brasil

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

Parasites of four ornamental fish from the Chumucuí River (Bragança, Pará, Brazil)

O objetivo do presente trabalho foi avaliar a fauna parasitária de quatro espécies de peixes ornamentais capturados no rio Chumucuí, no município de Bragança-PA. Foram coletados um total de 307 peixes pertencentes a 4 espécies, sendo elas: Moenkhausia sanctaefilomenae (olho de fogo, n = 23), Carnegiella strigata (borboleta, n = 37), Chilodus punctatus (cabeça-para-baixo, n = 7) e Astyanax bimaculatus (lambari, n = 240) coletados de junho de 2006 a dezembro de 2007. Foram observados 3 taxa parasitando os peixes: monogenéticos nas brânquias, nematóides (larvas de Capillaria sp. e Contracaecum sp.) no trato digestório e fígado e acantocéfalos (Quadrigyrus torquatus, Q. brasiliensis e Q. nickoli) no estômago e intestino. Astyanax bimaculatus apresentou maior prevalência de acantocéfalos na estação chuvosa, menor prevalência de nematóides na estação seca. Discute-se a eventual importância destes parasitas na exportação de peixes ornamentais.

Histological alterations in liver and testis of Astyanax aff. bimaculatus caused by acute exposition to zinc

This study investigated the effect of acute exposition to zinc (Zn) on histology of the liver and testes of yellow tail lambari (Astyanax aff. bimaculatus). The exposure consisted of six concentrations of Zn (0, 3, 5, 10, 15, and 20 mg/L) for 96 hours of exposure. Fragments of liver and testis were routinely processed and embedded in plastic resin based on glycol methacrylate. Fragments of bones, muscles, liver and testis were dehydrated and digested to quantify the absorption levels of Zn in the tissue. Acute exposure to concentrations above 10mg/L has produced structural changes in the liver and gonads. The changes found in the liver were vascular congestion; decrease of cellular volume; displacement of the hepatocyte nucleus; necrosis; disarrangement of cordon structure; leukocyte infiltrate and vacuolization. The changes found in the gonads were ruptured cyst, delayed development of germ cells, pyknotic nucleus, cell cluster, displacement of cyst wall and vacuolization. The histological changes observed were compatible with the increasing concentration of zinc in environment, compromising liver and reproductive functions, because there was an increase in relative frequency of hepatocytes and reduced sperm production

Comparative cytogenetics in Astyanax (Characiformes: Characidae) with focus on the cytotaxonomy of the group

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chromosomal Mapping of Repetitive DNA and Cytochrome C Oxidase I Sequence Analysis Reveal Differentiation among Sympatric Samples of Astyanax fasciatus (Characiformes, Characidae)

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