1Ohshima Experiment Station, Fisheries Laboratory, Kinki University, Kushimoto, Wakayama 649-3633, 2Graduate School of Agriculture, Kinki University, Naramachi, Nara 631-8505, 3Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, 4Graduate School of Fisheries Science, Hokkaido University, Hakodate, Hokkaido 041-8611, 5Fish Nursery Center, Kinki University, Kushimoto, Wakayama 649-3633, 6Uragami Experiment Station, Fisheries Laboratory, Kinki University, Nachikatsuura, Wakayama 649-5145, Japan
The hypoxic condition, which sometimes occurs in the high-density layer of fish eggs during the procedures of egg collection and transportation in aquaculture, is thought to be accompanied by hypercapnia. This study investigated the effects of hypoxia and hypercapnia for the striped jack Pseudocaranx dentex embryos during somitogenesis. The somitic disturbances in newly hatched larvae were induced by the extreme hypoxia of exposure to 0% dissolved oxygen (DO) concentration for 30 and 60 minutes. Extreme hypercapnia of 120 mg/L dissolved carbon dioxide (DCD) concentration for 90 or 120 minutes also induced the disturbances. The moderate hypoxic condition of exposure to 25% DO concentration for 60 and 90 minutes accompanied with hypercapnia of exposure to 120 mg/L DCD concentration induced somitic disturbances whereas this hypoxic condition alone did not induce them. The incidence rate of somitic disturbances was higher in the case of hypoxia of 25% DO and hypercapnia of 120 mg/L DCD than that in the case of normoxia of 100% DO and hypercapnia of 120 mg/L. These results indicate that hypoxia and hypercapnia during somitogenesis induce somitic disturbances as in other marine fishes and their coincidence promotes the induction in striped jack.