Swimming Behavioral Toxicity in JapaneseMedaka (Oryzias latipes) Exposed to Various Chemicals for Biological Monitoring ofWater Quality

Abstract

We conducted a short-term behavioral toxicity test in medaka (Oryzias latipes). Fish were exposed to toxicants (potassium cyanide [1 or 5 mg/L], phenol [12.5 or 25 mg/L], fenitrothion [10 or 20 mg/L], or benthiocarb [10 or 20 mg/L]), and swimming behavior was recorded and evaluated for 1 h. The medaka were placed in an exposure chamber with a continuous flow-through system. Two cameras tracked the fish at positions to the front and side of the test chamber, and images from the cameras were used to calculate the positions of the medaka in three dimensions (3D); the 3D data were processed by computer and analyzed as swimming activity (swimming speed and surfacing behavior).The swimming behavior of medaka was affected by exposure to toxic chemicals. The frequency of fast swimming was remarkably increased in medaka treated with potassium cyanide (5 mg/L), phenol (25 mg/L), or fenitrothion (10 or 20 mg/L). An increase in the time spent close to the water surface was observed in fish exposed to potassium cyanide (1 or 5 mg/L), fenitrothion (10 or 20 mg/L), or benthiocarb (20 mg/L). We concluded that pollution of water with these toxic chemicals at high concentrations can be detected by monitoring the swimming behavior of medaka for 1 h.