Efecto del acido araquidónico sobre la susceptibilidad al estrés por alta densidad, la producción de pge2 y la respuesta inmune del camarón blanco del pacifico Litopenaeus vannamei

Content Provider	Semantic Scholar
Author	Medina, Verónica Aguilar
Copyright Year	2009
Abstract	High stocking densities are highly desirable to increase yields in shrimp culture. However, concomitant stress negatively affects shrimp growth and health and particularly, immune response. The stress has been associated to physical (crowding) and to a physicochemical effect (crowding and poor water quality). The aim of the present work was to separate the physical and physicochemical stress of high stocking density in the Pacific whiteleg shrimp Litopenaeus vannamei, and to test the effect of supplying arachidonic acid (ARA) in the diet to decrease the negative effect of stress. Two experiments were simultaneously performed: in the first, shrimp were raised for 30 days in concrete tanks divided by a hard mesh that allowed water circulation; low or high densities were assigned to each one half of the tank in a way that the water was circulating between both groups but the crowding was different. In a second experiment, both halves of each tank were used for either high or low shrimp density, so in addition to crowding, the effect of water quality was observed. In addition, in both experiments diets enriched with a low (0.8%) and high ARA (3.2%) content were offered. Ammonia, temperature, dissolved oxygen, and feed consumption were analyzed periodically; temperature was constant among densities, but dissolved oxygen decreased as density increased, and ammonia increased at higher densities. After 30 days, shrimp were measured and weighted and metabolic (glucose, lactate, triacylglicerides, total lipids, glycogen, total proteins, and hemocyanin) and immune response (total hemocyte count, superoxide anion, and clotting time) in hemolymph and tissues were analyzed; as well as hemocyte fatty acid composition in phospholipids and reserve lipids. ARA is a precursor of prostaglandins from the series II (PGE2) which affects the immune system, so PGE2 was assessed in hemocytes and plasma. The high stocking density negative affected shrimp growth in both experiments, but the effect was more evident in the physicochemical experiment. Survival was not affected in either experiment. In the physical experiment, shrimp fed the low ARA diet showed a higher glucose and lactate concentration in hemolymph and a lower concentration of lactate in hepatopancreas and glycogen in muscle. In the physicochemical experiment an interaction was found, with higher glycogen levels in hepatopancreas in shrimp at higher density and fed the high ARA levels, and higher glycogen concentration in muscle in shrimp at higher density and fed the low ARA diet. Anion superoxide was not significantly affected in shrimp from the physical experiment, but an interaction was observed in shrimp from the physicochemical experiment, with higher production in shrimp fed the low ARA diet and lower production in shrimp fed the high ARA diet. The clotting time was affected by diet in both experiments, with lower values in shrimp fed the low ARA diet. In the physical experiment, PGE2 concentration in plasma was higher in shrimp fed the high ARA diet, but in the physicochemical experiment there were no significant differences for PGE2 levels ARA levels in the diet or density. The ARA levels had significant effect on the phospholipids and reserve lipids in the physicochemical experiment and on the ARA levels of phospholipids in the physical experiment. In conclusion, shrimp in the physical experiment were exposed to a long-term crowding stress, and responded by modifying metabolic and immune response, some of them possibly modulated by the ARA levels in the membranes of hemocytes. In contrast, shrimp in the physicochemical experiment exposed to a crowding and poor water quality stress, were more stressed and the immune and metabolic response was probably not enough, and thus, negative effects were observed on food consumption and growth. Feeding shrimp high levels of ARA reverted some of these negative effects, increasing growth and decreasing clotting time
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Language	English
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Resource Type	Article