低盐胁迫对银鲳幼鱼肠道消化酶活力的影响

通过逐级降低水体盐度的方法,将银鲳幼鱼分别在盐度25、20、15和10的条件下饲养至120 h,检测不同盐度下、不同时间点银鲳幼鱼肠道脂肪酶、淀粉酶、胰蛋白酶和胃蛋白酶的活力。结果表明,随着盐度的降低和处理时间的延长,脂肪酶的活力总体表现出先升后降的变化趋势(P0.05);淀粉酶的活力呈升高的变化趋势(P0.05);胰蛋白酶和胃蛋白酶活力的变化趋势不同,胰蛋白酶的活力呈现升高的趋势(P0.05),而胃蛋白酶活力呈下降的变化趋势(P0.05)。说明盐度降低会对银鲳幼鱼肠道的消化酶产生激活作用,从而促进肠道对营养物质的利用,达到补充机体所损失的能量的目的。但对于不同种酶,激活的顺序和程度却不尽相同,甚至当超出一定的耐受范围后,酶活力反而被抑制。在本研究中,随着盐度的下降和处理时间的延长,脂类物质首先被大量消耗,然后是淀粉类物质,而蛋白类物质在整个过程中的利用率较低。因此建议,在雨季来临之前,提高脂类和淀粉类物质的投喂量,将有助于提高幼体对低盐度的耐受性及其成活率。

Effects of low salinity on digestive enzyme activity in intestinal tract of juvenile silver pomfret Pampus argenteus

Effects of salinity on digestive enzyme activity of juvenile Pampus argenteus were investigated by progressively reducing water salinity.Four kinds of digestive enzymes(lipase,amylase,trypsin and pepsin) in intestinal tract of P.argenteus cultured at salinities 25,20,15 and 10 for 120 hours were analyzed.The results showed that: with the decreased salinity and the extension of processing time,lipase activity rose at first and then decreased at salinity 10,at the 120 h(P<0.05),while total amylase activity at salinity 10 was significantly higher than that at salinity 25(P<0.05).Trypsin and pepsin activity did not change significantly across salinities,though slight increases and decreases were observed at salinity 10 at 120 h compared with that at salinity 25 at 24 h(P<0.05).The results indicated that low ambient salinity could improve the activity of digestive enzymes in intestinal tract of P.argenteus,and the digestive enzymes could accelerate the utilizing of nutrients in intestine,so the consumed energy in osmoregulation could be compensated.However,the sequence and degree of activation for lipase,amylase,trypsin and pepsin were different,which indicated that salinity could increase the enzyme activity within some salinity range but it also could inhibit the activity beyond the range.So the study showed that,with the decreased salinity and the extension of processing time,first lipid was consumed,then the amylum,but the protein was not efficiently digested and absorbed in this process.So increasing the feeding of fatty and amylaceous nutrients before rainy season could enhance the tolerance and survival rate of juvenile P.argenteus under low salinity stress.