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The effect of sublethal concentrations of the water‐soluble fraction of crude oil on the chemosensory function of Caspian roach, Rutilus caspicus (YAKOVLEV, 1870)

The water‐soluble fraction of crude oil is a complex and toxic mixture of hydrocarbons. Because aquatic organisms directly encounter it, the water‐soluble fraction plays an important role in the toxicity of crude oil in aquatic environments. To determine whether fish are attracted to or avoid the water‐soluble fraction, Caspian roaches (Rutilus caspicus) were exposed to different concentrations of the water‐soluble fraction in a choice maze apparatus. The results showed that Caspian roaches can detect and avoid 2 mg/L of the water‐soluble fraction. To study the effect of the water‐soluble fraction on the olfactory function of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water‐soluble fraction for 96 h; afterward, exposed fish encountered food extract in a choice maze apparatus. The present study showed that the water‐soluble fraction significantly impairs the olfactory function of roaches. To investigate the effect of olfactory system dysfunction on the feeding behavior of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water‐soluble fraction. After 4 d, 8 d, and 12 d of exposure, the feeding behavior toward the food extract was tested. The results showed that both 3.2 mg/L and 16 mg/L of the water‐soluble fraction suppress the feeding behavior of Caspian roaches. The present study demonstrates that sublethal concentrations of crude oil's water‐soluble fraction impair the olfactory function of fish and consequently suppress the feeding behavior. Environ Toxicol Chem 2015;34:1826–1832. © 2015 SETAC