Common Carp (Cyprinus Carpio) Exposure to Water-Soluble Fraction (WSF) of Crude Oil: Evaluation of Protective Effects of Dietary Rosmarinus Officinalis Leaf on Water Quality, Growth Performance, Oxidative Stress, Stress Hormones and Heat Shock Proteins

The present study aimed to investigate the protective effects of dietary rosemary (Rosmarinus officinalis) leaf on water quality, growth performance, oxidative stress, stress hormones and heat shock proteins in common carp Cyprinus carpio (40.41±2.28 g). In a 56-day feeding trial, fish were exposed to water-soluble fraction (WSF) of crude oil (25 and 50% of the LC50 corresponding to 3.57 and 7.14 mg/l, respectively) and fed diets containing 0 and 0.1% rosemary. The results demonstrated that the concentrations of water quality parameters were within acceptable range and are sufficient to sustain common carp. The results showed a significant decrease in growth parameters and feed utilization in the WSF-exposed groups, whereas the growth parameters improved in the rosemary fed fish. The serum, liver and gill malondialdehyde (MDA), glutathione peroxidase (GPx) and superoxide dismutase (SOD) levels were significantly increased, whereas reactive oxygen species (ROS) and glutathione reductase (GR) were significantly (P<0.05) decreased in the WSF-exposed groups. The serum, liver and gill heat shock proteins (HSP70 and HSP90) were significantly increased in WSF-exposed groups. Similarly, the levels of triiodothyronine (T₃) and thyroxine (T₄) in serum and gill were significantly elevated in response to exposure of fish to WSF. The cortisol level in serum and gill tissues was significantly elevated in WSF fish versus the control. Acetylcholinesterase (AChE) level in serum and gill was significantly decreased in exposed groups compared with unexposed groups. In the liver, the level of T₄ and AChE was significantly (P<0.05) increased by exposing fish to WSF, whereas the level of T₃ showed an opposite trend. The cortisol level in liver was significantly (P<0.05) decreased especially in fish exposed to 50% of WSF. However, dietary supplementation of rosemary improved growth performance, feed utilization, oxidative stress markers, HSP and stress hormone parameters, especially in fish exposed to highest concentration. The results of the present study indicated that the exposure of common carp juveniles to sublethal concentration of WSF is capable of inducing homeostatic stress, leading to alterations in growth performance, heat shock proteins and stress hormone parameters of the common carp. Furthermore, inclusion of rosemary as a feed additive succeeded in improving growth performance and mitigating the deleterious effects of crude oil pollution in comparison to fish fed basal diet without rosemary supplementation.