Dynamics and cytochemistry of oogenesis in Astyanax fasciatus (Cuvier) (Teleostei, Characiformes, Characidae) from Rio Sapucaí, Minas Gerais State, Brazil

Oogenesis involves a set of transformations which are undergone by female germ cells These cells change into oogonias and then into mature oocytes. Sexually mature female fish were collected monthly, during one year, from the Sapucaí River, a tributary of the Rio Grande, which is part of the Furnas Reservoir in the state of Minas Gerais. During the several stages of maturation, we observed small round oogonias with a large nucleus, a single nucleolus, and weakly stained cytoplasm with eosinophilic granules. The primary oocytes showed a large basophilic nucleus, with a developed peripheral nucleolus and a reduced cytoplasm. The previtellogenic oocytes presented voluminous cytoplasm and nucleus with several small peripheral nucleoli. The oocytes underwent vitellogenesis with the development of the zona radiata and the follicle cells. Their cytochemical reactions indicated that the two layers of the zona radiata of A. fasciatus contained proteins and polysaccharides. The initially squamous follicle cells, became cuboidal. In mature oocytes, the nucleus moved toward the periphery, next to the micropyle, and the yolk granules formed by proteins, fulfilled the cytoplasm. The clear unstained vesicles are likely to be the cortical alveoli in the perivitelline region.

Dynamics and cytochemistry of oogenesis in Leporinus striatus Kner (Teleostei, Characiformes, Anostomidae) from the Rio Sapucaí, Minas Gerais State, Brazil

Oogenesis involves a sequense of transformations which are undergone by female germ cells. These cells change into oogonias and then into mature oocytes. Sexually mature females were collected monthly, during one year, from the Rio Sapucaí, tributary of the Rio Grande, which is part of the Furnas Reservoir system in the state of Minas Gerais. The observed material showed that oogonias were small spherical cells, had a big spherical nucleus, with a single nucleolus, and weakly stained cytoplasm with eosinophilic granules (FG stained), which indicate their protein content. The primary oocytes showed a big basophilic nucleus, with a large peripheral nucleolus, and several smaller nucleoli. They show a reduced cytoplasmic content. The previtellogenic oocytes presented voluminous cytoplasm and nucleus with several small peripheral nucleoli. The oocytes underwent vitellogenesis with the development of the zona radiata and the follicle cells. The zona radiata had two layers, the outer and the inner, which showed its protein content when stained with CM and FG techniques. TB pH 2.5 and pH 4.0 staining showed that oocytes undergoing vitellogenesis presented weakly stained cytoplasm and peripheral cytoplasmic vesicles. The follicle cells that were squamous became cuboidal. In mature oocytes, the yolk granules that filled the cytoplasm became green and blue when stained with FG and CM techniques, indicating their protein content. The perivitclline region showed rosy stained vesicles (TB pH 2.5 and pH 4.0) spread among the weakly stained peripheral vesicles, which seemed to be the cortical alveoli. The zona radiata cells, CM and FG stained, still showed two layers like the oocytes from the previous stage, but thicker.

Volumes de tanques-rede na produção da tilápia-do-nilo: estudo de caso

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

How the fluctuations of water levels affect populations of invasive bivalve Corbicula fluminea (Muller, 1774) in a Neotropical reservoir?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cyanobacteria and Cyanotoxin in the Billings Reservoir (São Paulo, SP, Brazil)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nenneguya garavelli n. sp and Myxobolus peculiaris n. sp (Myxozoa : Myxobolidae) in the gills of Cyphocharax nagelli (Osteichthyes : Curimatidae) from Rio do Peixe Reservoir, Sao Jose do Rio Pardo, São Paulo, Brazil

The present work describes myxozoans found in Cyphocharax nagelli (Characiformes: Curimatinae) commonly called saguiru collected from Rio do Peixe Reservoir, Sao Jose do Rio Pardo, São Paulo, Brazil. From a total of 38 examined fish, 24 were infected with Henneguya garavelli n. sp. (63% prevalence) and two with Myxobolus peculiaris n. sp. (5% prevalence) in the gills. Spores were studied by staining and fresh spores were observed by differential interference contrast optics. Henneguya garavelli n. sp. differs from Henneguya iheringi , Henneguya occulta, Henneguya cesarpintoi, Henneguya santae, Henneguya pisciforme, Henneguya amazonica, Henneguya striolata, Henneguya leporinicola and Henneguya chydadea in spore length and from Henneguya travassosi, Henneguya adherens, Henneguya malabarica, Henneguya piaractus and also Henneguya chydadea in polar capsule length and tail length. Myxobolus peculiaris n. sp. was very different when compared to other species of Myxobolus in its morphology and the biggest size of spore body. The authors present tables with comparative measurements of Brazilian myxozoan parasites. (c) 2006 Elsevier B.V. All rights reserved.

Description and prevalence of Thynnascaris sp. larvae Dollfus, 1933 (Nematoda: Anisakidae) in Plagioscion squamosissimus Heckel, 1840 from Volta Grande Reservoir, State of Minas Gerais, Brazil

O presente trabalho teve por objetivo o estudo da helmintofauna da corvina de água doce Plagioscion squamosissimus, do reservatório de Volta Grande, MG, Brasil. Foram colhidos 68 peixes com comprimento médio de 25,2 cm e peso médio de 180,9 g, com rede de espera, bimestralmente no período de dezembro de 1995 a dezembro de 1996. Os parasitos foram cuidadosamente retirados de seus cistos que estavam aderidos ao mesentério intestinal. Os espécimes foram fixados em AFA a 65°C e conservados em álcool 70°GL contendo 5% de glicerina. Após diafanização com ácido acético ou lactofenol de Amann, 21 nematóides foram desenhados em câmara clara. As larvas foram identificadas como Thynnascaris sp. (Nematoda: Anisakidae). Das 68 corvinas examinadas, 30 estavam infectadas por esses parasitos com uma prevalência de 44,1%. O número médio de parasitos por hospedeiro foi de 0 a 13,8 e a intensidade média, de 0 a 16. A análise estatística, de acordo com o Teste Exato de Fisher, mostrou que a sazonalidade foi dependente da pluviosidade e temperatura do ar.

Prevalence and histopathology of Neoechinorhynchus curemai Noronha, 1973 (Acanthocephala: Neoechinorhynchidae) in Prochilodus lineatus Valenciennes, 1836 from Volta Grande Reservoir, MG, Brazil

O presente trabalho estudou a prevalência e a histopatologia de Neoechinorhynchus curemai Noronha, 1973 (Acanthocephala: Neoechinorhynchidae) em curimbatá, Prochilodus lineatus Valenciennes, 1836. Dezoito peixes com comprimento total médio de 46,7 + 1,1 cm e peso médio de 1.674,8 + 75,6 g foram coletados com rede, bimestralmente, de dezembro de 1995 a dezembro de 1996 na usina hidrelétrica do Reservatório de Volta Grande (Cemig), Minas Gerais, Brasil. Dos peixes analisados, 15 estavam infectados com acantocéfalos no intestino (prevalência de 83,3%). A maior intensidade média ocorreu em agosto de 1996, com 66,5 (16 a 208) parasitos. A análise histopatológica revelou completa descamação do epitélio intestinal com severa hiperplasia e hipertrofia das células caliciformes. Observou-se, ainda, forte reação inflamatória na submucosa, deslocamento de feixes, associado a edemas, bem como infiltração mononuclear e eosinofílica.

Recent Studies on Neoechinorhynchus curemai Noronha, 1973 (Acanthocephala: Neoechinorhynchidae), in Prochilodus lineatus Valenciennes, 1836, from Volta Grande Reservoir, MG, Brazil

O presente trabalho estudou a helmintofauna do curimbatá, Prochilodus lineatus Valenciennes, 1836, do reservatório de Volta Grande, MG, Brasil. Foram analisados 18 peixes com comprimento médio de 46,7 ± 1,1 cm e peso médio de 1.674,8 ± 75,6 g, sendo que 15 apresentaram acantocéfalos no intestino com prevalência de 83,3%. O helminto foi identificado como Neoechinorhynchus curemai Noronha, 1973 (Acanthocephala: Neoechinorhynchidae), que diferiu das outras espécies descritas pelas dimensões dos caracteres e pela morfologia. da descrição original de N. curemai difere pelas maiores dimensões dos testículos, pela glândula de cimento alongada, pela presença de núcleos nos lemniscos, pelas dimensões dos ovos e pelos maiores ganchos da probóscide presentes na segunda e na terceira fileiras nos machos e na primeira fileira nas fêmeas. Foi observada menor porcentagem ocupada pelo sistema reprodutivo em relação ao tronco da fêmea. A observação dos parátipos de N. curemai de Noronha (1973) mostrou grande semelhança com os do presente trabalho. Este fato complementa a descrição do helminto em outra localidade.

Tetracaine stimulates insulin secretion through the mobilization of Ca2+ from thapsigargin- and IP3-insensitive Ca2+ reservoir in pancreatic beta-cells

The effect of tetracaine on Ca-45 efflux, cytoplasmic Ca2+ concentration [Ca2+](i), and insulin secretion in isolated pancreatic islets and beta-cells was studied. In the absence of external Ca2+, tetracaine (0.1-2.0 mM) increased the Ca-45 efflux from isolated islets in a dose-dependant manner. Tetracaine did not affect the increase in Ca-45 efflux caused by 50 mM K+ or by the association of carbachol (0.2 mM) and 50 mM K+. Tetracaine permanently increased the [Ca2+](i) in isolated beta-cells in Ca2+-free medium enriched with 2.8 mM glucose and 25 mu M D-600 (methoxiverapamil). This effect was also observed in the presence of 10 mM caffeine or 1 mu M thapsigargin. In the presence of 16.7 mM glucose, tetracaine transiently increased the insulin secretion from islets perfused in the absence and presence of external Ca2+. These data indicate that tetracaine mobilises Ca2+ from a thapsigargin-insensitive store and stimulates insulin secretion in the absence of extracellular Ca2+. The increase in Ca-45 efflux caused by high concentrations of K+ and by carbachol indicates that tetracaine did not interfere with a cation or inositol triphosphate sensitive Ca2+ pool in beta-cells.

Elimination and replacement of canine reservoir in an area endemic for visceral leishmaniasis

This work reviews studies about dog culling in Brazilian endemic areas for visceral leishmaniasis, as well as studies on dog replacement after euthanasia in areas where it is indicated as a control measure for this zoonosis.

Genetic diversity in Egeria densa and E. najas in Jupia Reservoir, Brazil

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

Catch and selectivity parameters of the anastomid fish Schizodon nasutus using gillnets in the Jurumirim reservoir (São Paulo, Brazil)

Catch and selectivity parameters using gillnets were calculated for Schizodon nasutus in the Jurumirim reservoir on the Parana-panema River in southern Brazil. The simple gillnets used were made of monofilament nylon of 30 to 140 mm mesh size an of different heights. The relative abundance of the S. nasutus caught was analysed monthly and a positive relationship was found between catches per unit effort in number and biomass. The relative catches were more abundant for the nets of 40 and 50 mm, mesh size. Catches were characterized by clear temporal variations and a predominance of medium size fish throughout the study period. The selectivity curve of gillnets for S. nasutus in this ecosystem was obtained. The catch obtained was compared with the available catch for each mesh size, and the available catch for a certain length of fish was calculated starting from the theoretical selectivity curve. The 50 mm mesh size gillnet showed the best fit between real and available captures and was considered the most suitable, because a smaller mesh size resulted in a catch of predominantly immature specimens. It is expected that these results will contribute to improving management strategies for conservation of resources. Parameters such as the minimum catch length advisable or the mesh size permitted for a given species are indispensable for such decision-making.

Population structure and stock assessment of Hoplias malabaricus (Characiformes: Erythrinidae) caught by artisanal fishermen in river-reservoir transition area in Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Length-weight relationships for 20 species collected in the Jurumirim reservoir (Paranapanema Basin, Brazil)

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