RESUMO
Objetivo. Analizar el efecto combinado de salinidad (5, 15, 25, 35 y 45ups) y temperatura (15, 20, 25, 30 y 35°C) sobre la supervivencia y frecuencia de mudas en postlarvas (PL12) de Litopenaeus vannamei. Materiales y métodos. Los experimentos se realizaron por cuadriplicado por cada combinación de salinidad y temperatura. Las postlarvas se mantuvieron en acuarios de 3 L a una densidad de 100PL/l. La salinidad se incrementó disolviendo sal granulada libre de yodo, a partir de agua de mar, mientras que para alcanzar las salinidades menores se utilizó agua dulce filtrada. Las postlarvas aclimatadas a 35ups y 28°C (condición inicial) fueron sometidas abruptamente a las salinidades y temperaturas experimentales por 30 minutos. Después, se filtraron y se colocaron nuevamente en su condición inicial para su recuperación. Transcurridos 30 minutos, se contaron las postlarvas vivas y las mudas. Los datos fueron analizados por un ANOVA de dos vías. Resultados. Se determinó que la supervivencia y frecuencia de mudas fueron significativamente afectadas por la salinidad, temperatura y su interacción (p<0.05). Se obtuvo una supervivencia máxima y mínima de 99.8 y 94.4%. Los porcentajes de supervivencia y frecuencias de mudas disminuyeron a una baja salinidad en combinación a bajas y altas temperaturas, y aumentaron independientemente de la salinidad y temperatura, a excepción de 5ups con 15, 30 y 35°C. La mortalidad máxima de postlarvas fue de 5.6% (5ups y 30°C). Conclusiones. Se determinó que a temperaturas de 20 y 25°C en combinación a las salinidades utilizadas, fueron las mejores condiciones de supervivencia y de resistencia de las postlarvas ante dichas condiciones hidrológicas.
Objective. The combined effect of salinity (5, 15, 25, 35, and 45psu) and temperature (15, 20, 25, 30, and 35°C) was evaluated on survival and molt frequency in Litopenaeus vannamei postlarvae (PL12). Materials and methods. Four repetitions were applied to each combination of salinity and temperature. The PL were placed in 3 L beakers at a density of 100PL/l. Salinity was increased by dissolving commercial salt without iodine, into marine water, whereas fresh filtered tap water was used to decrease the salinity from seawater. The PL were adapted at 35psu and 28°C (initial conditions) during 30 minutes. Thereafter, they were transferred to each experimental combination of salinity and temperature by 30 minutes. Following this procedure, the PL were filtered and returned to their initial acclimatization conditions. After 30 minutes of recuperation, the live PL and molts were counted. All data were analyzed using a two-way ANOVA. Results. Survival and molt frequency were significantly (p<0.05) affected by salinity, temperature and the interaction of both factors. The maximum and minimum survival rates of 99.8 and 94.4% were obtained. Survival and molt frequency rates were significantly (p<0.05) affected by salinity, temperature and the interaction of both factors. Survival and molt frequency percentage rates decreased at lower salinity in combination with lowest and highest temperatures, and significantly increased, independently from salinity and temperature conditions, with exception of 5psu at 15, 30 and 35°C. The highest mortality rate (5.6%) was obtained at 5psu and 30°C. Conclusions. It was determined that survival of postlarvae was higher at temperatures of 20 and 25°C given salinity combination, which are considered the best conditions for survival and resistance.