Hypoxia tolerance and antioxidant defense system of juvenile jumbo squids in oxygen minimum zones

► To investigate the antioxidant stress strategies of juvenile D. gigas in normoxia and hypoxia. ► Higher SOD and CAT activities constituted an integrated stress response in normoxia. ► Elevated heat shock response (Hsp70/Hsc70) while in the OMZ may be a “preparation for oxidative stress”. ► Lipid peroxidation remained stable indicating no enhancement of cellular damage during the night upwards migration.