In this study, the marine medaka Oryzias javanicus was exposed to two concentrations of non-toxin-producing red tide dinoflagellate C. polykrikoides (1,000 and 2,000 cells ml-1) for 96 h, and the time-course biochemical responses of antioxidant and immunity parameters were analyzed in the liver tissue. Significant ichthyotoxicity with increasing cell concentrations of C. polykrikoides and exposure period was observed for 96 h. Opercular respiratory rate was lowered in marine medaka exposed to 2,000 cells ml-1 of C. polykrikoides. Intracellular malondialdehyde (MDA) content significantly elevated in response to both cell concentrations. In the case of glutathione (GSH) content, the levels were significantly elevated by 1,000 cells ml-1 of C. polykrikoides, but the contents significantly depleted upon exposure to 2,000 cells ml-1 of C. polykrikoides. Similarly, enzymatic activities of catalase (CAT) and superoxide dismutase (SOD) were increased by 1,000 cells ml-1 of C. polykrikoides, whereas their activities were lowered by 2,000 cells ml-1 of C. polykrikoides. Analysis of the two immunity parameters, alternative complement pathway and lysozyme, showed significantly lowered activities in 2,000 cells ml-1 of C. polykrikoides-exposed liver tissue. These biochemical effects of C. polykrikoides on marine medaka would be helpful for understanding its acute effects in marine fish.

Introduction
Material and Methods
    1. Experimental animals
    2. Analysis of acute effects of C. polykrikoides
    3. C. polykrikoides exposure and sample preparation
    4. Biochemical analysis
    5. Statistical analyses
Results
    1. Survival and respiration rate
    2. Malondialdehyde and glutathione content
    3. Antioxidant defense parameter
    4. Immune parameter
Discussion

• Seong Duk Do(Department of Marine Science, College of Natural Sciences, Incheon National University, Incheon 22012, Korea)
• Yun Kyung Shin(Aquaculture Industry Research Division, South Sea Fisheries Research Institute, National Institute of Fisheries Science, Jeonnam 59780, Korea)
• Jae-Sung Rhee(Department of Marine Science, College of Natural Sciences, Incheon National University, Incheon 22012, Korea, Yellow Sea Research Institute, Incheon 22012, Korea) Corresponding author