大型围栏养殖模式下2种规格斑石鲷耐高温研究

Thermal Tolerance of Two Sizes of Spotted Knifejaw(Oplegnathus punctatus) in Offshore Aquaculture Net Pen

鱼类作为水生变温动物,围栏圈养环境海水温度的突变会对其机体正常的生理活动产生显著影响。本研究以2种规格斑石鲷(Oplegnathus punctatus)为实验对象,分析了急性高温(32℃)胁迫后1、3、6 h,恢复正常温度(25℃)后6 h和12 h时,其呼吸频率、血清中葡萄糖(GLU)和皮质醇(COR)含量、血液中红细胞(RBC)和白细胞(WBC)数目、血红蛋白(HGB)含量、红细胞积压(HCT)以及肝脏热休克蛋白(hsp70、90)mRNA表达量的变化。结果显示,32℃高温条件下,2种规格斑石鲷呼吸频率呈先升高后降低的变化趋势,其中,50 g和200 g斑石鲷分别在0.3 h(20 min)和1 h时呼吸频率达最高值(P<0.05)。2种规格斑石鲷COR和GLU浓度皆呈先升高后降低的变化趋势,50g斑石鲷COR浓度在1h时显著高于其他处理组(P<0.05),GLU浓度在6h时显著高于其他处理组(P<0.05);200 g斑石鲷COR浓度在1 h时显著低于50 g斑石鲷血清COR浓度(P<0.05),恢复6 h后,COR浓度与对照组相比无显著差异(P>0.05),GLU浓度在高温胁迫期间一直处于较高水平,恢复12 h时与对照组相比无显著差异(P>0.05)。高温胁迫过程中,50 g斑石鲷WBC、RBC、HGB含量呈先上升后下降的趋势,200g斑石鲷WBC、RBC、HCT处理组与对照组相比无显著差异(P>0.05),HGB含量呈先上升后下降的趋势,3h时显著高于对照组(P<0.05)。高温诱导2种规格斑石鲷肝脏组织中hsp70和hsp90 mRNA表达量皆呈先上升后下降的趋势,hsp70和hsp90mRNA表达量分别在3 h和1 h达到最高(P<0.05)。上述指标在恢复正常温度(25℃)12 h后,恢复至正常水平,同对照组无显著差异(P>0.05)。综上,急性高温刺激显著增加了2种不同规格斑石鲷的呼吸频率、COR和GLU含量,上调了肝脏hsp70和hsp90 mRNA表达,小规格的斑石鲷应对高温胁迫具有更强适应调节能力。相关结果为斑石鲷大型围栏养殖提供了有效数据支撑,同时也为进一步阐明斑石鲷高温耐受调控机制奠定了基础。

Offshore aquaculture net pens have the characteristics of open spaces, vast waters, and natural environments. This is one of the important ways to expand aquaculture space, create a new production base for high-quality protein, and develop deep and offshore sea aquaculture. A sudden change in ambient water temperature may significantly affect the normal physiological status of fish as they are ectotherms. In the present study, respiratory frequency, serum cortisol and glucose concentrations, the hematological index, and hepatic hsp70 and hsp90 mRNA expression were determined during various thermal durations and recovery periods to illustrate the thermal tolerance and the underlying physiological response of two sizes of spotted knifejaw. The respiratory frequency of the two sizes of spotted knifejaw first increased and then decreased subject to thermal stress at 32℃, with the highest value(P<0.05)observed at 0.3(20 min) and 1 h in 50 and 200 g fish, respectively. The serum cortisol and glucose concentrations of the two sizes of spotted knifejaw showed similar trends to the respiratory frequency. In 50 g spotted knifejaw, the serum cortisol concentration was significantly higher at 1 h(P<0.05) and the serum glucose concentration was significantly higher at 6 h(P<0.05) than that in the other treatment groups. However, in 200 g spotted knifejaw, serum cortisol and glucose concentrations remained high under thermal stress. Hematological data of the two sizes of spotted knifejaw were rather different.Specifically, the number of white blood cells(WBCs), red blood cells(RBCs), and hemoglobin(HGB) in the blood of 50 g spotted knifejaw first increased and then decreased and were significantly higher than that in the control group at 3 h(P<0.05). In 200 g spotted knifejaw, no significant changes in WBC, RBC,and hematocrit were noted(P>0.05), although HGB showed an initial increase, followed by a decreasing trend and was significantly higher than that in the control group at 3 h(P<0.05). The hepatic hsp70 and hsp90 mRNA expression of the two sizes of spotted knifejaw increased first and then decreased. As such,hsp70 mRNA expression was the highest at 3 h, while hsp90 mRNA expression was the highest at 1 h(P<0.05). In conclusion, acute thermal stress significantly increased the respiratory rate and serum cortisol and glucose concentrations of two different sizes of spotted knifejaw and upregulated hepatic hsp70 and hsp90 mRNA expression;all aforementioned parameters gradually recovered to normal levels after treatment at 25℃ for 12 h. Meanwhile, small spotted knifejaw manifested greater thermal tolerance.These results provide useful data for spotted knifejaw culture in offshore aquaculture net pens and can strengthen our understanding of the regulatory mechanism of spotted knifejaw temperature tolerance.