Two HSPs gene from juvenile Amur sturgeon (Acipenser schrenckii): cloning, characterization and expression pattern to crowding and hypoxia stress.

In this study, the cDNA sequences of HSP70 and HSP90 were isolated from the special chondr-ganoid scale, Amur sturgeon, for the first time. Homology analysis indicated that amino acid sequences of HSP70 and HSP90 shared high identity with other species (82.68-99.07 and 90.19-98.07%, respectively). The tissue expression analysis showed that the asHSP70 and asHSP90 mRNA were ubiquitously expressed in all the examined tissues under unstressed condition. The expression pattern of HSP70 and HSP90 under chronic (crowding) and acute (hypoxia) stress was examined by q-PCR in liver, spleen and kidney. Results showed that stocking density could significantly influence the expression of HSP70 at day 20 and/or day 40. In contrast to stocking density, levels of HSP70 transcripts indicated a remarkable increase in all examined tissues after hypoxia stress. HSP90 levels in liver and spleen increased significantly in high stocking density. By comparison, significant increase of asHSP90 in kidney was only found in high stocking density at day 40. Similar to HSP70, the levels of HSP90 transcripts showed significant increases after hypoxia stress except the transcript of liver in H2 group 6 h after hypoxia. The assessment of asHSP70 and asHSP90 mRNA levels under crowding and hypoxia stresses indicated that asHSP70 and asHSP90 gene might be good indicators of stressful situations for Amur sturgeon. Taking serum globulin and electrolytes account, we suggest that crowding and hypoxia stress can result in considerable stress for Amur sturgeon.

The physiological performance and immune responses of juvenile Amur sturgeon (Acipenser schrenckii) to stocking density and hypoxia stress.

Stocking density and hypoxia are considered priority issues in aquaculture research. In this study, two experiments were carried out in order to investigate the effects of chronic stress (stocking density) and acute stress (hypoxia) on the immune physiology responses (hematology, serum cortisol, glucose, total protein and the mRNA expression of CYP 1A) of juvenile Amur sturgeon (Acipenser schrenckii). In the chronic stress study, three triplicate groups of Amur sturgeon (42.0 ± 2.3 g) were reared in nine square concrete ponds (4.4 × 4.4 × 0.45 m³) at three stocking densities (3.7, 6.9 and 9.0 kg/m³) for 50 days. In the acute stress study, three triplicate groups: normal group (7 mg/l), hypoxia group 1 (5 mg/l) and hypoxia group 2 (3 mg/l) were used in nine 100 L indoor tanks. Sampling was performed at the end of the stocking density experiment (50 days) and at 0, 0.5, 1.5, 3 and 6 h after hypoxia stress. The results showed that increased stocking density reduced the morphological indexes (hepatosomatic index, spleen-somatic index and kidney-somatic index), while total protein and hemoglobin increased significantly in the stressed group. In response to hypoxia, the levels of cortisol, glucose and hematological parameters elevated significantly after this stress. As for spleen-somatic index, there was a decline after hypoxia though H1 group returned to the normal level at 3 h and 6 h after hypoxia stress. Additionally, In order to better understand the immune response of Amur sturgeon to chronic and acute stressors, we cloned the complete coding sequence of Amur sturgeon CYP 1A for the first time and investigated its tissue-specific expression and stress-induced expression. CYP 1A mRNA in liver showed over expressions both in crowding condition and in hypoxia stress. The same trend was also found in spleen and kidney which may provide evidence that CYP 1A could serve as a good indicator of immune response in Amur sturgeon. In addition, the result suggested a typical immune response both in high stocking density and hypoxia stress. But the chronically stressed fish might have an adaptation capability to survive under a stable crowding condition without a change in some immune parameters (cortisol, glucose, WBCs and RBCs).