Resumo

RE, Ana Denisse; DIAZ, Fernando; SIERRA, Elizabeth  e  GOMEZ-JIMENEZ, Silvia. Oxygen consumption, ammonium excretion and osmoregulatory capacity of Litopenaeus stylirostris (Stimpson) exposed to different combinations of temperature and salinity. Cienc. mar [online]. 2004, vol.30, n.3, pp.443-453. ISSN 0185-3880.

The physiological responses of the blue shrimp were determined by exposing the organisms to temperatures of 23°C, 28°C and 33°C, and salinities of 10, 15, 20, 25, 30, 35 and 40%o. Oxygen consumption of Litopenaeus stylirostris exposed to experimental salinities increased in direct relationship with temperature, even though at 28°C the metabolic rate was steady. The ammonium excretion rate in juvenile shrimp acclimated at 23°C and 33°C was related to the pattern of osmoregulation, increasing when the shrimp were hyper-regulators and decreasing when they were hypo-regulators. The ammonium excretion rate remained constant in shrimp kept at 28°C. The osmoregulatory capacity of the juveniles indicated that they were hypo-regulators and hyper-regulators in salinities above and below the isosmotic point, this capacity decreasing in organisms kept at 33°C and exposed to higher salinities. The isosmotic point obtained ranged from 676.8 to 700.7 mmol kg^-1 (23.7-24.6%o). The values of the slopes between the osmotic concentration of the external medium and the hemolymph of shrimp acclimated at 23°C, 28°C and 33°C were 0.25, 0.17 and 0.3, respectively; the lowest value was obtained for juveniles maintained at 28°C, being strong regulators in this condition. To optimize the culture of L. stylirostris under controlled conditions, we propose that it be cultivated in salinities of 25%o and temperatures of 28°C, considered the optimum conditions because in these environments the organisms are free of stress and their growth therefore increases.

Palavras-chave : oxygen consumption; ammonium excretion; osmoregulatory capacity; temperature and salinity; Litopenaeus stylirostris.

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