The utilization of probiotic bacteria have been widely tested and applied in intestinal microflora modulation, through competitive exclusion of the pathogenic bacteria. Aeromonas hydrophila is a gram-negative bacterium, responsible for fish outbreaks in farms around the world, and is one of the major loss causes for neotropical fish farmers. 660 pacus (67 ± 7 g) were distributed in 20 tanks (n = 33), constituting five groups (four tanks for each treatment): four groups were fed with different levels (2, 4, 8 and 16 g kg −1) of Bacillus cereus and Bacillus subtilis (1:1, 10 8 CFU g −1), and the fifth group was fed with a control diet (without probiotic). Pacus fed with probiotic showed increment in the ROS production associated to elevated neutrophil and monocyte counts and increased phagocytic activity without affecting the growth parameters. Probiotic fed fish presented higher survival rates, subjected to an i.p. challenge with 10 8 CFU mL −1 of A. hydrophila. The results demonstrated a dose response effect and the ideal level of the probiotic (Bacillus cereus and Bacillus subtilis, 1:1, 10 8 CFU g −1) in P. mesopotamicus diets was around 8 g kg −1 , as the highest survival rates and immunological responses were found in groups of fish fed with this diet. In addition, too much probiotic should be avoided, as pacus fed diet with 16 g kg −1 showed partial suppression of these responses.
Parasitic diseases have caused significant problems to global aquaculture production. These studies will further our knowledge of this complex problem and help implement adequate prevention measures and control strategies. The present study aimed to investigate the presence of parasites in Megaleporinus obtusidens and to describe the epidemiology and pathology of parasitic infections in these fish. Five moribund fish were sent for parasitological examination. The integument and gills were scrapped off with a glass slide, and samples were examined under a light microscope. Parasitic crustaceans found in these specimens were submitted for scanning electron microscopy and histological analyses. The crustaceans Dolops carvalhoi and Lernaea cyprinacea and the Epistylis spp. were present in all fish examined. Epistylis spp. were also seen on the entire surface of the crustacean integument. Microscopic lesions observed in the parasitized gills included hyperplasia and hypertrophy of the lamellar epithelium, an inflammatory infiltrate, telangiectasia, foci of hemorrhage and necrosis, fusion of the secondary lamellae, and detachment of the lamellar epithelium. Crustacean parasites are important mechanical vectors of Epistylis infection and disseminate the disease in fish farming operations. Epistylis spp. infection affects the health of fish and has significant ecological and economical impact on aquaculture.
RESUMO.-[Anticoagulante Na 2 EDTA danifica amostras de sangue do teleósteo Piaractus mesopotamicus.] O presente estudo teve por objetivo avaliar os efeitos da heparina sódica e Na 2 EDTA no sangue de Piaractus mesopotamicus (360,7±42,4g, 26,4±1,0cm). Foram amostrados vinte peixes em dois ensaios experimentais, sendo dez peixes utilizados para análise da fragilidade dos eritrócitos e dez peixes para análise dos parâmetros hematológicos e estudo bioquímico do plasma. O sangue coletado por punção veno-caudal foi aliquotado e armazenado em diferentes soluções anticoagulantes: Na 2 EDTA 10%, Na 2 EDTA 3%, heparina sódica 5.000 UI e heparina sódica 100 UI. Níveis plasmáticos de cálcio apresentados nas amostras armazenados em Na 2 EDTA diminuíram cerca de 80% em relação aos dois grupos armazenados com heparina. Amostras de sangue de pacus armazenados com Na 2 EDTA demonstraram aumento do hematócrito e VCM, e diminuição na CHCM. O efeito dose-resposta foi observado neste estudo. Estes resultados são reforçados pelos níveis mais elevados de proteína plasmática e hemólise apresentado no sangue armazenado com Na 2 EDTA 10%, o que confirma o efeito deletério desse tratamento anticoagulante na qualidade de amostras de sangue. Na 2 EDTA não é indicada para armazenar amostras de sangue de P. mesopotamicus, e heparina sódica a 100 UI é o anticoagulante mais recomendado, uma vez que este tratamento apresentou a menor taxa de alterações no sangue armazenado. The present study aimed to evaluate the effects of Na heparin and Na 2 EDTA on blood of Piaractus mesopotamicus (360.7±42.4g, 26.4±1.0cm). Twenty fishes were sampled in two experiment trials, ten for erythrocyte fragility analysis and ten for hematologic and plasma biochemical study. The blood collected by venous-caudal puncture was fractioned and stored in anticoagulants solution: Na 2 EDTA 10%, Na 2 EDTA 3%, Na heparin 5000 IU and Na heparin 100 IU. Plasmatic levels of calcium presented in the Na 2 EDTA stored samples were about 80% lower than both heparin groups. Blood samples of P. mesopotamicus stored with Na 2 EDTA demonstrated increase in the hematocrit and MCV, and decrease in MCHC. The dose-response effect was observed in this study. The results are reinforced by the higher levels of plasmatic protein and hemolysis presented in the Na 2 EDTA 10% stored blood, confirming the deleterious effect of this anticoagulant treatment on the quality of blood samples. Na 2 EDTA is not indicated to store P. mesopotamicus blood samples, but sodium heparin at 100 IU is the most recommended anticoagulant, since this treatment presented the lower rate of alterations in the stored blood. INDEX TERMS: Fish hematology, blood clotting, EDTA, Heparin, Piaractus mesopotamicus.
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