Consumo de oxígeno, excreción de amonio y capacidad osmorreguladora de Litopenaeus stylirostris (Stimpson) expuesto a diferentes combinaciones de temperatura y salinidad Oxygen consumption, ammonium excretion and osmoregulatory capacity of Litopenaeus stylirostris (Stimpson) exposed to different combinations of temperature and salinity

The physiological responses of the blue shrimp were determined by exposing the organisms to temperatures of 23oC, 28oC and 33oC, and salinities of 10, 15, 20, 25, 30, 35 and 40‰. Oxygen consumption of Litopenaeus stylirostris exposed to experimental salinities increased in direct relationship with temperature, even though at 28oC the metabolic rate was steady. The ammonium excretion rate in juvenile shrimp acclimated at 23oC and 33oC 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 28oC. 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 33oC and exposed to higher salinities. The isosmotic point obtained ranged from 676.8 to 700.7 mmol kg–1 (23.7–24.6‰). The values of the slopes between the osmotic concentration of the external medium and the hemolymph of shrimp acclimated at 23oC, 28oC and 33oC were 0.25, 0.17 and 0.3, respectively; the lowest value was obtained for juveniles maintained at 28oC, being strong regulators in this condition. To optimize the culture of L. stylirostris under controlled conditions, we propose that it be cultivated Ciencias Marinas, Vol. 30, No. 3, 2004