Acute toxicity of ammonia and nitrite in juvenile clownfish Amphiprion ocellaris
Author: Rafael Soriani Medeiros (Currículo Lattes)
Supervisor: Dr Ricardo Vieira Rodrigues
Co-supervisor: Dr Luís André Nassr de Sampaio
Abstract
The clown fish Amphiprion ocellaris is often reared at high stocking densities which, added to the high protein levels of the foods used, increase the concentrations of ammonia and nitrite, which are toxic compounds and can cause fish mortality. In the present study, juveniles (1.20 ± 0.34 g) of A. ocellaris were exposed to six concentrations of ammonia (0.23; 0.57; 0.97; 1.05; 1.22 55 and 1, 63 mg/L NH3-N) and eight nitrite concentrations (26.28; 53.26; 72.48; 111.27; 56 132.38; 157.42; 178.37 and 202.18 mg/L NO2 -N). The median lethal concentrations (LC50) were estimated for 24, 48, 72, and 96 hours of exposure to these compounds, being 1.06; 0.83; 0.75 and 0.75 mg/L NH3-N and 188.29; 151.01; 124.06 and 108.79 mg/L NO2-N, respectively.Histological analyzes of the gills revealed lesions such as hyperplasia of the epithelium of the primary lamellae, hyperplasia and hypertrophy of the chloride cells and epithelial elevation. However, the frequency of injuries increased with increasing levels of ammonia and nitrite in the water. Fish exposed to 0.57 mg/L NH3-N or 100 mg/L NO2-N also showed lamellar fusion. Histopathologies were significantly higher in fish exposed to 0.57 mg/L NH3-N or 25 mg/L NO2 - N compared to control fish. Therefore, special attention is recommended for ammonia and nitrite levels in A. ocellaris cultivation systems.57 mg/L NH3-N or 100 mg/L NO2-N also showed lamellar fusion. Histopathologies were significantly higher in fish exposed to 0.57 mg/L NH3-N or 25 mg/L NO2 - N compared to control fish. Therefore, special attention is recommended for ammonia and nitrite levels in A. ocellaris cultivation systems.