| The offspring by distant hybridization between Pagrosomus Major♀and Sparus Macrocephalus♂were successful cultivation by Ningbo Academy of Ocean and Fishery. After initial culture experiment, we found the hybrid with fast growth rate and broad salt, temperature optimum. The study on the anti-adversity of P.major♀×S. macrocephalus♂F1 was carried out with the purpose to determine whether the hybrid is a good fish species.The main results and conclusions are as follows:⑴The ability of resistance to hypoxiaHematological parameters Erythrocyte quantity in the hybrid (3.13×109) was similar to S. macrocephalus (3.27×109), however, it is significant different from P. major (2.25×109). In the aspect of Hb concentration, serum iron, TIBC, UIBC, Iron saturation of the hybrid were intermediate to the P. major and S. macrocephalus. The hybrid had the most complicate serum transferring polymorphism.Oxygen consumption rate Oxygen consumption rate and asphyxia point of P. major, S. macrocephalus and the hybrid were tested at the temperature of 19.7～21.3℃. The average OCR of the hybrid was 0.235mg/g·h, higher than S. macrocephalus (0.215mg/g·h), lower than P. major (0.281mg/g·h). The hybrid had a lower head floating point than P. major and S. macrocephalus. In the aspect of asphyxia point the hybrid was similar to S. macrocephalus, but significantly lowers than P. major.⑵Hypoxia-induced hematological parameters, enzymatic activies in P. major, S. macrocephalus and their hybridThe effects of hypoxia 12h on the levels of hemoglobin concentrations, red blood cell count, and the activities of antioxidant enzymes were measured in the blood, liver, gill, and muscle of the P. major, S. macrocephalus and their hybrid.The hybrid in hypoxia had a significantly higher RBC increased (32.3%) than P. major (26.2%) and S. macrocephalus (31.2%). In the aspect of Hb concentration, the hybrid was similar to the P. major (25.2% and 24.4%), but lower than S. macrocephalus (30.7%). As regards to metabolic and antioxidant enzymatic activies, the hybrid was intermediate to the P. major and S. macrocephalus. ⑶Hypoxia-induced metabolic and antioxidant enzymatic activies in the hybridTo examine hypoxia-induced stress at metabolic and antioxidant enzyme levels, we exposed the P. major♀×S. macrocephalus♂F1 to 1.83±0.27mg/L dissolved oxygen. After 0, 6, 12 and 24h exposure, samples of liver, gill, and muscle tissue were extracted and subsequently analyzed for lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), and total anti-oxidative capability (T-AOC). LDH content rose within 6h of hypoxia in the muscle (25.7%), but return to control levels during longer hypoxia exposure. Liver showed decreased activity of CAT under hypoxia but LDH, SOD and T-AOC responded with sharp increases in activities (17.6%, 20.2% and 54.1% respectively). Gill showed minor changes in LDH and CAT activities under hypoxia exposure but an increase in T-AOC activity (239%). The results show that the hybrid can respond quickly to hypoxia, and have a certain degree of hypoxia tolerance, but its long hypoxia stress may cause oxidative damage.⑷Disease resistanceThe median lethal does (LD50) was different to the Vibrio alginolyticus (1.0×109CUF/ml) for P. major and S. macrocephalus and their hybrid at 10-0.9,10-1.74,10-1.48, respectively. The most sensitive was the S. macrocephalus, followed by the hybrid, and then the P. major.The hybrid had a better performance in phagocytic index and respiratory burst of head kidney cell. In the aspect of percentage of phagocytic and lysozyme activity, the hybrid was intermediate to the Pagrosomus Major and Sparus Macrocephalus; for the other two traits, AKP and ACP, the hybrid and Sparus Macrocephalus was similar, but they were lower than Pagrosomus Major(P<0.05). Therefore, it can be generally concluded that the hybrid had a higher resistance to disease than Sparus Macrocephalus, but lower than Pagrosomus Major.Hematological parameters, antioxidant enzyme and non-specific immunity were studied to compare the anti-adversity among P. major, S. macrocephalus and their hybrid. The result showed that the hybrid was a good fish species with great potential for exploiting.
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