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Abstract

The effects of nitrite concentration on larval development of Amazon river prawn, Macrobrachium amazonicum, were studied in laboratory. In Experiment 1, larvae were reared in 600-mL glass beakers filled with 300-mL water with nitrite concentration of 0, 0.2, 0.4, 0.8 and 1.6 mg/L NO2-N. In Experiment 2, total ammonia nitrogen (TAN, NH3-N + NH4-N) excretion were analyzed in zoea (Z) I, III, VII and IX exposed to 0, 0.4, 0.8 and 1.6 mg/L NO2-N. In both experiments each treatment was conducted in five replicates. The experiments were carried out in test solutions at 10 salinity, constant temperature 30 C and 12:12 h daylight : darkness regime. Survival, productivity, weight gain and larval stage index decreased linearly with increasing ambient nitrite concentration. However, there was no significant difference among larvae reared at concentration ranging from 0 to 0.8 mg/L NO2-N by ANOVA in all variables. Individual ammonia-N and mass-specific ammonia-N excretion increased in ZI and ZIX, was almost constant in ZIII and decreased in ZVII from 0 to 1.6 mg/L NO2-N. The relationship between individual TAN and body mass suggested that 1.6 mg/L NO2-N stress the larvae. Despite of the effects of nitrite on larvae follow a dose-dependent response and shows large variability among individuals, levels below 0.8 mg/L may be used as a general reference in commercial hatcheries, which should be applied carefully.