Evaluation of the effects of ammonia-induced stress on hematologic, stress factors and gill histology of Banded Cichlid (Heros severus)

As a chemical stressor, increasing ammonia concentration in water can causes non-specific physiological responses in fish. The present research was done to determine the suitable amount of ammonia and its effects on hematologic, stress factors and histology of gill in banded cichlid (Heros severus). For this purpose, 1 control group and 5 treatments of ammonia (0.1, 0.2, 0.4, 0.8, and 1.2 mg/l) with three replicates were selected. 180 specimens were transported to different concentrations of ammonia in 50-liter tanks for 12 hours. After blood sampling, hematologic and stress factors were measured. In addition, their gill tissues were sampled. The results showed that white blood cells reached its peak in Treatment 3 (P<0.05). The lowest red blood cells were observed in Treatment 5 (P<0.05). When concentration of ammonia was increased, the amount of HB, Htc, MCV, MCH, MCHC, Monocytes and eosinophils didn’t have significant difference (P>0.05). The results showed that cortisol increased in the first two treatments and then decreased in the next three treatments. In addition, glucose reached its minimum level in the first treatment and then showed a significant increase in other treatments (P<0.05). The most tissue damages were observed in Treatment 5 along with hypertrophy of lamella epithelial cells, adhesion of lamellae, lamella detachment and bulging, filament epithelium necrosis, severe necrosis in the lamella and filament epithelial, and necrosis and demolition of pillar cells. Therefore, it is better for banded cichlid to the amount of ammonia does not increase more than 0.1 mg/l.