Effects of salinity stress on anxiety behavior and antioxidant capability of guppy (Poecilia reticulata)

The objective of this study was to determine the effect of salinity on anxiety behavior and liver antioxidant capacity in the guppy (Poecilia reticulata). Guppies were exposed to salinities of 0 parts per thousand, 5 parts per thousand, 10 parts per thousand, 15 parts per thousand and 20 parts per thousand for acute stress tests, and then we analyzed the activity of antioxidant enzymes at 3, 6, 12, 24, 48, 72 and 96 h. During the experiment, the anxiety behavior of guppy was enhanced at salinities of 10 parts per thousand, 15 parts per thousand, and 20 parts per thousand, as evidenced by a significantly higher latency time for the first passage through the upper part than that of the control group (P < 0.05). CAT activity was highest at 24 h in the treatment with the salinity of 10 parts per thousand, and SOD and GPX activities were highest at 12 h into the treatment with the salinity of 10 parts per thousand. The SOD and CAT activities were significantly higher than the control group after 96 h of treatment at different salinities (P < 0.05). The MDA contents of the experimental groups at salinities of 5 parts per thousand and 10 parts per thousand were not significantly different from the control group after 96 h of treatment (P > 0.05). While the MDA contents of the experimental groups at salinities of 15 parts per thousand and 20 parts per thousand were still significantly higher than the control group after 96 h of treatment (P < 0.05). The experimental results indicated that elevated salinity could lead to oxidative stress in the guppy, altering their anxiety behavior as well as the activity of antioxidant enzymes. In conclusion, drastic changes in salinity during culture should be avoided.