Response and recovery of Nile tilapia exposed to diesel oil – Behavioral, hemato-biochemical and morphological changes of erythrocytes

Pollution caused by petroleum oil in several manners is becoming a threat to aquatic ecosystem. Hence, we carried out an experiment to investigate how diesel oil affects biota behavior, physiological attributes and how they recover by using Nile tilapia (Oreochromis niloticus) as a model organism. Nile tilapia of two different treatment groups were exposed to 0.1 mL/L and 0.5 mL/L diesel oil for 7 days. Then both groups were kept in completely diesel oil-free water for 14 days. A control group was maintained throughout the experimental period. We examined the behavioral attributes, hemato-biochemical parameters: hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC) and glucose (Glu), and morphological changes of erythrocytes after diesel exposure and at the end of recovery phase. Our results revealed that there were abnormalities in behavior and significant changes in Hb, RBC, WBC and Glu level in both of the treatment group after 7 days of exposure. Frequencies of erythrocytic cellular abnormalities (ECAs), for example, twin, spindle, elongated, tear drop and erythrocytic nuclear abnormalities (ENAs) like notch nuclei, karyopyknosis, nuclear bud and nuclear bridge were prominent in both groups. However, the amount of anomalies was higher in most if not all the cases in 0.5 mL/L treatment group. Nile tilapia of both groups were quick to recover but the 0.1 mL/L group showed profound recovery than the 0.5 mL/L group. However, in the cases of ECAs and ENAs, recovery of the 0.5 mL/L group was insignificant. Hence, our experimental study concluded that the higher the exposure to diesel oil, higher incidences of major health problems are recorded, seriously piercing the healing system of Nile tilapia.