微颗粒饲料与冷藏桡足类对大黄鱼稚鱼消化酶活力、肠和肝脏显微结构的影响

EVALUATION OF MICRODIETS AND FROZEN COPEPODS ON DIGESTIVE ENZYME ACTIVITIES,INTESTINAL AND LIVER MICROSTRUCTURES OF LARGE YELLOW CROAKER (PSEUDOSCIAENA CROCEA R.) LARVAE

以初始体重(13.80±0.40)mg的大黄鱼(Pseudosciaena crocea R.)稚鱼为对象,在室内系统内进行饲养试验,研究了新开发的3种微颗粒饲料(Diet 1–Diet 3)、混合饲料(Diet 4:Diet 3和冷藏桡足类)与冷藏桡足类(Diet 5,对照组)对25—60日龄大黄鱼稚鱼消化酶活力、肠和肝脏显微结构的影响。结果显示,35和60日龄时,微颗粒饲料组鱼苗间的胰蛋白酶活力差异不显著(P>0.05),但均较25日龄时高,而混合组和对照组无显著变化。除对照组鱼苗35日龄时的胰淀粉酶活力显著(P<0.05)高于25和60日龄外,其他各组间均无显著差异。随着鱼苗的生长,除混合组和对照组外,各组间鱼苗肠道氨肽酶和碱性磷酸酶活力均逐渐升高。组织学结果显示,混合组35日龄鱼苗前中肠黏膜上有大量脂滴,而其他各组鱼苗则没有。微颗粒饲料组鱼苗肠黏膜褶皱比混合组和对照组多且深,直肠黏膜上皮细胞中可见脂滴积累,而对照组鱼苗直肠几乎没有褶皱,并缺乏脂滴。微颗粒饲料组鱼苗肝细胞内有大量脂滴,胞核移向细胞外周。混合组鱼苗35日龄时肝细胞内也有脂滴,但数量在60日龄时减少。对照组鱼苗肝脏中可见类似于饥饿状态的胞间隙、细胞质塌陷和胞核固缩。以上结果表明,合适的微颗粒饲料可促进大黄鱼稚鱼消化道的发育。基于Diet 1效果优于Diet 2和Diet 3,可将其作为进一步研究大黄鱼稚鱼营养和微颗粒饲料的基础配方。

A feeding trial was conducted to evaluate effects of three newly developed microdiets （MDs： Diet 1-Diet 3）, a mixed diet （Diet 4： Diet 3 combined with frozen copepods） and frozen copepods （Diet 5, control） on digestive enzy matic activities, intestine and liver microstructures of large yellow croaker （Pseudosciaena erocea R.） larvae, which had an initial mean body weight of （13.80 ±0.40） mg from 25 to 60 days after hatching （DAH）. The results showed that trypsin activities exhibited no significant difference between fish fed with the MDs at 35 and 60 DAH, although those at 25 DAH showed lower trypsin activities, and there was no significant difference between fish fed with mixed diet and frozen copepods. No significant differences were observed between fish fed with the experimental diets except frozen copepods, the latter led to higher amylase activity at 35 DAH than at 25 and 60 DAH. As fish grew older, aminopepti- dase N and alkaline phosphatase activities increased in fish fed with the experimental diets except for Diet 4 and Diet 5. No lipid droplets were observed in anterior mediate intestinal mucosa in 35-day-old fish that were fed with the experi- mental diets with the exception of the Diet 4. Fish fed with the MDs presented deeper intestinal mucosa folds and su pranuclear vacuoles in the rectum, while rectal folds from fish fed with the frozen copepods were nearly flat and lacked supranuclear vacuoles. Fish fed with the MDs displayed numerous lipid vacuoles in hepatocytes with nuclear migration. Liver from fish fed with the mixed diet had numerous lipid vacuoles in hepatocytes with nuclear migration at 35 DAH but such vacuoles decreased at 60 DAH. Liver from fish fed with the frozen copepods resulted in some intercellular spaces, collapsed cytoplasm and pycnotic nuclei of hepatocytes that were similar to starvation condition. These results indicated that suitable MDs could improve the development of digestive system of large yellow croaker larvae. Diet 1 can be used as basal formula for further research on nutrition and MD for large yellow croaker larvae because it was superior to Diets 2 and 3.