The hybrid Pelteobagrus fulvidraco (?) x Leiocassis longirostris (?) exhibits improved trait on hypoxia-tolerance

Hypoxia has become a significant issue both in open aquatic environment and closed aquaculture system. Development of hypoxia-tolerant breeds is one of the practical strategies in further fish farming. In present study, the hybrid Pelteobagrus fulvidraco (PF) x Leiocassis longirostris (LL) was generated by artificial insemination. Both PF female x LL male and LL female x PF male could produce F1 offspring, assigned as hybrid PL and hybrid LP, respectively. The hybrid PL exhibited higher hatching rate, expectant morphological traits, and an improved trait on hypoxiatolerance compared to hybrid LP. However, the growth trait was not strengthened at early development stage until 90 dpf compared to hybrid LP and LL. To further examine the hypoxia-tolerant machinery of the hybrid PL strain, we systematically investigated the tissues morphology, hypoxia inducible factor (HIF)-related genes expression, and oxidative stress enzymes activity of gill, liver, and intestine under acute hypoxia and reoxygenation. The histological results showed that the interlamellar cell mass was expanded in the gill, obvious vacuolation and swell of hepatocytes was found in the liver, and expanded submucosa was observed in the intestine, suggesting the tissues remodeling was evidenced in hybrid PL responding to hypoxia. A rapid HIF-related genes response (Hif-1 alpha, Hif-2 alpha, Vhl, Fih-1, Phd3, and Vegf-a) and activation of anti-oxidant enzymes activity (TSOD, CAT, and GPx) among three tissues were patently illustrated. Our results indicated that the complex combination of morphological, molecular, and biochemical adjustments might contribute jointly to the hypoxiatolerance of hybrid PL. This study provided an alternative and possible method for hypoxia-tolerant fish strain generation using hybridization breeding in aquaculture.