This investigation aimed to assess the appetite response changes of olive flounder to starving and re-feeding conditions. Three different feeding groups (2 weeks feeding, fed; 2 weeks starving, starved; and 1 week starving and 1 week feeding, re-fed) were established to examine the changes in appetite-related genes for each group. The weight gain of the fish was highest for the fed group and lowest for the starving group. Based on the daily feed intake (DFI) and cumulative feed intake (CFI), overall food intake was found to increase in the re-fed group more than in the fed group from week 1 to week 2 of the experiment. Hypocretin neuropeptide precursor (HCRT) and galanin receptor 1 (GAL-R1) mRNA expression in the brain of olive flounder were decreased in the starved group. Corticotropin-releasing hormone (CRH) was decreased in all experimental groups, except for the fed group. However, overall leptin concentrations in the plasma did not change across groups. Considering the differences between this study and previous studies on starving and feeding, various factors (except the production and expression mechanisms of appetite-related factors in response to starving) are likely acting on the appetite responses of the fish. In this study, a 1-week re-feeding period induced substantial effects on appetite response when compared to a 2-week feeding period. These findings show that even if re-feeding is performed after starving, the unbalance caused by the re-feeding can affect various physiological changes in fish by feed intake efficiency.

Introduction
Materials and Methods
    1. Experimental fish
    2. Fasting and feeding experimental conditions
    3. Survival rate and weight gain
    4. Food intake
    5. Total RNA extraction and cDNA synthesis
    6. Real-time quantitative polymerase chain reaction(qPCR) analysis
    7. Plasma parameter analysis
    8. Statistical analysis
Results
    1. Weight gain and changes in feed intake
    2. Changes in HCRT expression
    3. Changes in GAL-R1 expression
    4. Changes in CRH expression
    5. Changes in the plasma leptin concentration
Discussion

• Min Ju Kim(Department of Convergence Study on the Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea)
• Jin Ah Song(Marine Bio-Resources research Unit, Korea Institute of Ocean Science and Technology, Busan 49111, Korea)
• Cheol Young Choi(Department of Convergence Study on the Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea, Division of Marine BioScience, Korea Maritime and Ocean University, Busan 49112, Korea) Corresponding author