Impact of transient temperature disturbance on the oxidative stress indices and glucose levels of juvenile Koi carps (Cyprinus carpio var koi)

Background: The present study reports the changes in the redox state and glucose activity in gills and muscles of Koi carps, exposed to a short duration of acute thermal stress. The variation in levels of lipid peroxidation (LPO) and glutathione (GSH), catalase (CAT) and glutathione-S-transferase (GST) activity, in addition to glucose levels, were analysed after exposing the fishes to 15 degrees C (low), 25 degrees C (control) and 35 degrees C (high) for a duration of 3 and 6 h. The upper and lower temperatures regimes were decided by the Critical Thermal Limit (CTMAX and CTMIN). Results: The CAT activity was high in both the tissues at 35 degrees C within 3 h, while LPO activity decreased throughout the study when compared with the control group indicating immoderate cellular disturbance and surplus oxidative stress. At 15 degrees C (3 h), tissues reported more glucose compared with the upper thermal slab. GSH increased in both the tissues at 15 degrees C compared with the control for 3 and 6 h. GST activity, however, flourished at 35 degrees C in muscles and gills for the 3-h regime. Conclusion: The current study demonstrated disturbing impacts of temperature on the survivability of the Koi carps in a domesticated environment.