In vivo ovarian and testicular stress responses in Adult Koi carp (Cyprinus carpio) under chronic hypoxia

摘要

Cyclic hypoxia ( DO < 0.8 mg/L) forms oxidative stress in gonads of reproductively active koi carp through formation of Reactive Oxygen Species (ROS). Testis due to its higher energy requirements for spermatogenesis is one of the most afftected organ under chronic hypoxia in fish. ATPase activity in testicular cells decrease drastically under hypoxia (p < 0.05) which compelled male koi carps to divert energy towards basic metabolism for survival than reproduction. Decreased ovarian ATPase activity was not that severe to stop oogenesis as few mature oocytes were evident in ovary of hypoxic females. Higher LDH activity in testicular cells under hypoxia is a result of forced entry into anerobic phase of cell metabolism. Under this anerobic condition certain anti-oxidant enzyme like catalase and SOD activity significantly increased in testicular cells as well as in follicular cells to prevent oxidative damages during gametogenesis and sex-steroid production. Primary stress responses like significantly elevated blood glucose and serum Cortisol, decreased serum protein level were evident in male fishes than females during hypoxic stress. Cyclic hypoxia has caused significant loss of male GSI by using storage lipid and protein for Cortisol mediated gluconeogenesis as a primary stress response. Therefore oxidative stress is a major factor in the aetiology of male infertility and reproductive inhibition in female during hypoxia.