Mortality, hematology, and histopathology of common snook Centropomus undecimalis (Perciformes: Centropomidae) exposed to acute toxicity of ammonia

Abstract

ABSTRACTThis study aimed to evaluate the tolerance of common snook Centropomus undecimalis larvae and juveniles exposed to acute concentrations of un-ionized ammonia for 96 h at 35g L−1 salinity, after 24 h starvation. For that, 10 larvae (20.85 ± 1.46 mm) of 47 days post hatch (DPH) per experimental unit (1.5 L) were exposed to 0.00 ± 0.00, 0.65 ± 0.04, 1.29 ± 0.09, 2.59 ± 0.18, 3.88 ± 0.27, 5.17 ± 0.34, and 6.47 ± 0.43 mg L−1 NH3, in triplicates, at 26.72 ± 0.08°C, dissolved oxygen at 5.72 ± 0.10 mg L−1 and pH 8.45 ± 0.06. During this period, no mortalities were observed. Another trial was performed with five juveniles (20.35 ± 6.10 g, 13.90 ± 1.75 cm) per experimental unit (60 L) exposed to 0.00 ± 0.00, 2.26 ± 0.07, 2.68 ± 0.11, 3.20 ± 0.13, 3.68 ± 0.17, and 4.27 ± 0.16 mg L−1 NH3, in triplicates, at 21.90 ± 0.76°C, dissolved oxygen at 6.27 ± 0.21 mg L−1 and pH at 8.38 ± 0.04. Fish mortality increased as ammonia concentrations increased at each day, and LC50 96 h was 3.52 mg L−1 NH3. Larvae were less sensitive than juveniles, demonstrating that the environmental toxicity of ammonia to common snook is influenced by age. Sublethal exposition to ammonia caused histological damages in gills of common snook juveniles and variation on glucose levels, hematocrit, and red blood cells number, showing negative effects on fish homeostasis. Moreover, compared to other species, the common snook has great resistance to ammonia.