Effect of diesel oil exposure on behavioral, hemato-biochemical, and morphological changes of erythrocytes and recovery pattern analysis of Nile tilapia (Oreochromis niloticus)

Abstract

Pollution due to petroleum oil by various means is becoming a threat to aquatic ecosystems. Hence, we carried out an experiment to explore how diesel oil affects the behavioral and physiological attributes of fish and how they recover by using Nile tilapia (Oreochromis niloticus) as a model organism. The Nile tilapia of 2 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 glucose levels in both of the treatment groups 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 anomalies were higher in most if not all the cases in the 0.5 ml/l treatment group. Fish in both groups were quick to recover and the 0.1 ml/l group showed profound recovery than the 0.5 ml/l group. However, in the case 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 degrading the healing system of Nile tilapia.