Dermocystidium sp. infection in farmed striped catfish Pangasianodon hypophthalmus farmed in Ceará state, Northeastern Brazil.

The genus Dermocystidium infects a wide range of animals. The host infection often occurs through the ingestion of endospores. The diagnosis depends on wet mounts and histopathological analysis of the affected tissue. The aim of this study was to investigate the incidence of Dermocystidium sp. infection on the skin of farmed striped catfish (Pangasianodon hypophthalmus) from a fish farm located in Fortaleza, Ceará state, northeastern Brazil. From these observations, we determined that 100% of the analyzed animals were infected with Dermocystidium sp. The wet mount and histopathology of the fish lesions revealed spore-filled cysts between the dermis and epidermis, encapsulated by connective tissue. Owing to a lack of research on the parasite and its prevalence among different fish species in Brazil and the rest of the world, additional studies are required to understand their endemicity in fish farms of Brazil, and consequently develop better disease prevention methods and increase the overall productivity.

Parasitological diagnosis in food fish produced in a fish farm, in the Zona da Mata, Minas Gerais, southeastern Brazil.

This study identified the parasitic species in juvenile freshwater finfishes during the fattening stage, from a fish farm located in the Zona da Mata (MG), southeastern Brazil, and revealed both macro and microscopical lesions in fish gills. A total of 172 juvenile fishes of different species (Oreochromis niloticus, Ictalurus punctatus, Ctenopharyngodon idella, Cyprinus carpio, Astyanax bimaculatus and Brycon amazonicus) were transported to a laboratory in São Paulo city. The fish were sedated and then euthanized for parasitological analysis. All fish were infected by at least one parasite species. Ten different species of parasites were identified: Apiosoma sp., Epistylis sp., Ichthyobodo sp., trichodinids, Piscinoodinium pillulare, Ichthyophthirius multifiliis, Tetrahymena sp., monogeneans, Centrocestus formosanus metacercariae, and Dermocystidium sp. The best management practices and lack of sanitary control were also discussed.

Acute exposure to hyperosmotic conditions reduces sperm activation by urine in the yellowtail tetra Astyanax altiparanae, a freshwater teleost fish / Exposição aguda a condições hipereosmoticas reduz ativação do sêmen por urina em lambari do-rabo-amarelo (Astyanax altiparanae), um teleósteo de água doce

In freshwater fish with external fertilization, sperm sampling can be contaminated with urine, which triggers motility and gives rise to decreased fertilization success. The maintenance of freshwater fish in hyperosmotic conditions may reduce urine production and improve sperm quality. Thus, the aim of this work was to verify if acute exposure to various NaCl concentrations improves sperm quality in the yellowtail tetra Astyanax altiparanae. Spermiation was induced using a single dose of carp pituitary gland (5 mg kg-1) and the males were maintained at various NaCl concentrations: NaCl 0.00% (control), NaCl 0.45% (hypoosmotic), NaCl 0.9% (isosmotic) and NaCl 1.0% (hyperosmotic) for 6 h at 26 °C. Sperm was collected and verified for activation by urine and motility traits. At 0.00%, 0.45%, and 0.90%, the sperm was motile just after sampling, indicating activation by urine. Surprisingly, at hyperosmotic conditions, no activation was observed. Other sperm and motility parameters did not show any statistical differences, including sperm viability (P = 0.7083), concentration (P = 0.9030), total motility (P = 0.6149), VCL (curvilinear velocity; P = 0.1216), VAP (average path velocity; P = 0.1231) and VSL (straight-line velocity; P = 0.1340). Our results indicate that acute maintenance at hyperosmotic conditions eliminates sperm activation by urine and maintains sperm quality. Such a new procedure is interesting for both basic and applied sciences, including reproductive practice in fish.(AU)

Em peixes de água doce com fertilização externa, a amostragem de espermatozoides pode ser contaminada pela urina, o que desencadeia motilidade e gera menor sucesso na fertilização. A manutenção de peixes de água doce em condições hiperosmóticas pode reduzir a produção de urina e melhorar a qualidade do esperma. Assim, o presente trabalho foi delineado para verificar se a exposição aguda a várias concentrações de NaCl melhora a qualidade do esperma no tetra-amarelo Astyanax altiparanae. A espermiação foi induzida usando uma dose única de hipófise da carpa (5 mg kg-1) e os machos foram mantidos em várias concentrações de NaCl: NaCl 0,00% (controle), NaCl 0,45% (hipoosmótico), NaCl 0,9% (isosmótico) e NaCl 1,0% (hiperosmótico) por seis horas a 26 °C. O esperma foi colhido e verificado quanto à ativação por urina e traços de motilidade. Em 0,00%, 0,45%, 0,90% os espermatozóides eram móveis logo após a amostragem, indicando ativação pela urina. Surpreendentemente, em condições hiperosmóticas, nenhuma ativação foi observada. Outros parâmetros espermáticos e de motilidade não mostraram diferenças estatísticas, incluindo viabilidade espermática (P = 0,7083), concentração (P = 0,9030), motilidade total (P = 0,6149), VCL (Velocidade Curvilinear; P = 0,1216), VMD (Velocidade Média de Deslocamento; P = 0,1230) e VLR (Velocidade em linha Reta; P = 0,1340). Nossos resultados indicam que a manutenção aguda em condições hiperosmóticas elimina a ativação do esperma pela urina e mantém a qualidade do esperma. Esse novo procedimento é interessante para as ciências básicas e aplicadas, incluindo a prática reprodutiva em peixes.(AU)