Evaluation of hypoxia tolerance in F3 hybrids of blunt snout bream (Megalobrama amblycephala♀) × topmouth culter (Culter alburnus♂)

Abstract

To compare gill hypoxia adaptation mechanisms, the hypoxia-related physiological indices were measured in F3 self-crossing population of blunt snout bream (Megalobrama amblycephala)♀ × topmouth culter (Culter alburnus)♂ hybrids. The critical oxygen pressure (Pcrit) of F3 population was 28.33 ± 1.58 Torr, which is higher than topmouth culter (21.69 ± 0.85 Torr) and lower than blunt snout bream (33.00 ± 0.97 Torr). Moreover, the lower oxygen tension threshold for loss of equilibrium (LOEcrit) of F3 hybrids was 1.09 mg·L−1 higher than topmouth culter (0.91 mg·L−1) and lower than blunt snout bream (1.30 mg·L−1). These results indicated that the hypoxia tolerance of F3 hybrid fish was significantly higher than that of blunt snout bream. In the hypoxic environment, gill remodeling reactions increased the mass-specific lamellar area. In this study, gill remodeling was observed in blunt snout bream, topmouth culter and F3 hybrids. However, a particularly intriguing finding was that the gill recovery ability of F3 population was better than that of blunt snout bream after reoxygenation treatment. This might be related to the capability of physiological and biochemical regulation and lactic acid excretion of F3 hybrids. Together, these results showed that the F3 population inherited the gill remodeling mechanism of their parents, which had better hypoxia tolerance than blunt snout bream, and they could change the morphology and physiological and biochemical levels of gill tissue to cope with hypoxia.