慢性氨氮胁迫对刺参摄食与消化酶活性的影响

以刺参(Apostichopus japonicas Selenka)为研究对象,探讨氨氮胁迫浓度为0 mg/L、2 mg/L、4 mg/L、6 mg/L、8 mg/L、10 mg/L时14 d内刺参摄食情况与消化道内3种不同消化酶活性变化。刺参规格分别为小S,体重(15.13±0.02)g]、中M,体重(28.42±0.32)g]、大L,体重(60.14±0.88)g]。结果显示:(1)随着氨氮浓度的升高,实验刺参存活与生长逐渐与对照组出现显著差异。当氨氮浓度高于2 mg/L时,刺参末体重与特定生长率随氨氮浓度升高有显著下降趋势;当氨氮浓度为8~10 mg/L时,3种不同规格刺参均出现了吐肠、化皮,直至死亡,氨氮浓度为10 mg/L时中规格刺参存活率最低,为81.3%。(2)当氨氮浓度低于10 mg/L时,氨氮胁迫对3种规格刺参摄食率(FR)影响差异不显著,而全部实验组的食物转化率(FCE)均显著低于对照(P0.05)。(3)氨氮胁迫对3种不同规格刺参消化酶活性的影响存在差异。随氨氮浓度升高,蛋白酶活性呈降低趋势,氨氮浓度8 mg/L和10 mg/L时全部实验组刺参蛋白酶活性显著低于对照(P0.05);脂肪酶和淀粉酶活性随氨氮浓度升高呈先升后降趋势,在2 mg/L时出现峰值;当氨氮浓度为6 mg/L时,小规格刺参的消化道淀粉酶活性降低到0.30 U/mg(prot),与对照出现显著差异(P0.05);当氨氮浓度从6 mg/L到8 mg/L时,3种规格刺参脂肪酶活性发生急剧变化,显著低于对照(P0.05),中规格刺参在同一氨氮浓度胁迫下的消化酶活性变化显著高于其他规格。研究表明,氨氮胁迫会对刺参摄食、消化与生长产生不利影响,在氨氮浓度4 mg/L以下刺参消化酶活性短期可被显著诱导上调,高氨氮浓度对消化酶活性起抑制效应并可导致生理紊乱,此响应存在体重规格上的差异。

Effects of chronic ammonia nitrogen stress on the feeding and digestive enzyme activities of sea cucumber (Apostichopus japonicas Selenka)

This study was conducted to evaluate the effects of chronic ammonia nitrogen (N) stress (concentration gradient:0 mg/L, 2 mg/L, 4 mg/L, 6 mg/L, 8 mg/L, 10 mg/L) on the feeding and activities of three types of digestive enzymes (protease, amylase, lipase) in sea cucumbers (Apostichopus japonicas Selenka) of three different sizes (initial body weights:15.13±0.02 g, 28.42±0.32 g, and 60.14±0.88 g) over a 14-day period. The results obtained were as follows. (1) With an increase in ammonia-N level, the survival and growth of sea cucumbers were significantly different from those in the control group. When the ammonia-N level was higher than 2 mg/L, the final body weight and specific growth rate of sea cucumbers show a marked downward trend with an increase in ammonia concentration. As the ammonia-N level increased to 8 and 10 mg/L, all sea cucumbers of the three different sizes appeared evisceration, with skin ulceration until death. When the ammonia-N level was 10 mg/L, the survival rate of medium-sized sea cucumbers reached 81.3%, the lowest among the three sizes. (2) When the ammonia-N level was lower than 10 mg/L, the effect of ammonia-N stress on the feeding rate of sea cucumbers of all three weights was not significant (P>0.05), whereas the food conversion efficiency of all the experimental groups was significantly lower than that of the control group (P<0.05). (3) There were significant differences in the digestive enzyme activities of the three-sized sea cucumbers under the stress of ammonia-N. With an increase in ammonia concentration, protease activities decreased. When the ammonia-N level was 8 mg/L and 10 mg/L, the protease activities of all the experimental groups were significantly lower than those in the control group (P<0.05). With an increase in ammonia concentration, the activities of lipase and amylase initially increased and then decreased, peaking at 2 mg/L. When the ammonia-N level was 6 mg/L, the amylase activity of the small-sized sea cucumbers decreased to 0.30 U/mg protein, which was significantly different from the control group (P<0.05). When the ammonia-N level was from 6 mg/L to 8 mg/L, the activity of lipase in the three-sized sea cucumbers was markedly affected, being significantly lower than that in the control group (P<0.05). Under the same ammonia concentration, the activities of digestive enzymes in the medium-sized sea cucumbers were significantly higher than those in the other sizes. These results indicate that ammonia-N stress can affect the feeding and digestive enzyme activities of sea cucumbers. Therefore, in the process of sea cucumber breeding, particularly in large-scale seed culture, it is preferable to control the concentration of ammonia-N in the water environment to within 4 mg/L.