Hematologia de tilápia-do-nilo alimentada com suplemento à base de algas frente a desafios de estresse agudo e crônico / Hematology of Nile tilapia fed supplementation with algae challenged by acute and chronic stress

Avaliou-se o efeito da suplementação com produto à base de algas, ergosan, em dietas para tilápias Oreochromis niloticus, submetidas ao desafio de estresse agudo e crônico sobre as características hematológicas. O ensaio foi realizado com tilápias jovens (15g) em caixas de 500L de capacidade de estocagem, em sistema com recirculação da água, com fluxo constante, na densidade de 35 peixes por caixa. Os peixes foram alimentados com as dietas-teste durante 10 dias e, ao final deste período, voltaram a receber dieta isenta de ergosan, quando foram submetidos aos desafios de estresses agudo e crônico. Utilizou-se o delineamento inteiramente ao acaso (DIC), em esquema fatorial 4x2, sendo testados: quatro porcentagens do suplemento 0; 0,25; 0,5 e 1 por cento de ergosan na ração em dois tipos de estresse, agudo e crônico. Os resultados permitem concluir que os estímulos de estresse aplicados foram capazes de provocar alterações fisiológicas nos peixes, incluindo redução no número de eritrócitos, eritroblastos e leucócitos e aumento do volume corpuscular médio dos eritrócitos. A administração oral de 1 por cento de suplemento durante 10 dias para juvenis de tilápia-do-nilo, em condição de estresse agudo, induz o incremento de 69 por cento no número de trombócitos circulantes.

The aim of this trial was to evaluate hematological parameters of tilapia Oreochromis niloticus fed diet supplemented with ergosan, an algae product, in a chronic and acute stress challenge. The experiment was carried out with juvenile tilapias Oreochromis niloticus (15g), in 500 L-tanks linked at a water recirculation system, with constant water flow and controlled temperature, stoking 35 fish/tank. Fish were fed test-diets during 10 days and, at the end of this period, received a diet without supplementation, when they were submitted to chronic and acute stress challenge. Fish were distributed in a completely randomized design, in a factorial scheme 4x2: four supplement levels (0; 0.25; 0.5 and 1 percent supplement in the diet) with two stresses (chronic and acute). Results showed the stress stimulus applied were able to induce physiologic changes on fish, including reduction of erythrocytes, erythroblasts and leucocytes number and increasing medium corpuscular volume. Oral administration of 1 percent supplement during 10 days for Nile tilapia juveniles under acute stress induces a higher thrombocyte number (69 percent) in the blood.

Effect of dietary supplementation with vitamin E and stocking density on macrophage recruitment and giant cell formation in the teleost fish, Piaractus mesopotamicus.

The effect of dietary supplementation with 0, 100 and 450 mg of vitamin E (DL-alpha tocopheryl acetate)/kg of a dry diet on the kinetics of macrophage recruitment and giant cell formation in the pacu, maintained at different stocking densities (5 kg/m(3) and 20 kg/m(3)), was investigated by insertion of round glass coverslips into the subcutaneous connective tissue. After a feeding period of 18 weeks, the coverslips were implanted and later removed for examination at 2, 7 and 15 days post-implantation. Fish fed diets supplemented with 450 mg of vitamin E showed an increase (P<0.05) in the accumulation of macrophages, foreign body giant cells and Langhans type cells. The kinetics of macrophage recruitment and giant cell formation on the glass coverslips appeared to be strongly influenced by vitamin E supplementation, since fish fed a basal diet and held at high stocking densities showed low numbers of adhering cells on the coverslips, and high concentrations of plasma corticosteroids. On the other hand, fish given a diet supplemented with 450 mg of vitamin E did not show a similar difference in plasma cortisol concentrations related to stocking density. The effect of cortisol concentrations on carbohydrate metabolism, analysed by assessment of plasma glycaemia, was not clear. Blood glucose concentrations did not vary substantially with the different treatments examined. These results suggest that vitamin E may contribute to the efficiency of the fish's inflammatory response by increasing macrophage recruitment and giant cell formation in the foreign body granulomatous reaction. Vitamin E appeared to act on the stress response of pacus by preventing a stress-related immunosuppression.

Piscinoodinium pillulare (Schaperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the Northeast region of São Paulo State, Brazil: parasitological and pathological aspects

The Aquaculture Center of Unesp, Jaboticabal, SP, Brazil, received fishes for diagnosis from fish farmers reporting fish crowding at pond edges and in water inlets. Fifty-three out of 194 cases showed round to oval, immobile whitish structures, measuring up to 162 mm diameter, identified as the dinoflagellate Piscinoodinium pillulare. In 34 diagnosed cases the parasites were present in the gills, in 2 on body surface, and 9 in both. Thirty-one out of 53 were tambacu hybrids hosts; 7, Piaractus mesopotamicus; 6, Colossoma macropomum; 5, Leporinus macrocephalus; 3, Oreochromis niloticus; and 1, Prochilodus lineatus. Fish showed increased mucous production on body surface and gills, while ecchymosis in the caudal peduncle and operculum was present. The gills also showed paleness, congestion, and petechiae. Histopathology presented a great number of trophonts situated between secondary lamellae, fixed to or detached from the epithelium. Primary lamellae presented interstitial hemorrhages, severe hyperplasia of the epithelium, goblet cells, and mononuclear infiltrates. The present work is the first report of P. pillulare in Brazil and emphasizes the importance of this dinoflagellate which caused significant economic losses from 1995 through 1997