氨氮对中国对虾抗病力的影响

EFFECT OF AMMONIA-N ON ANTI-DISEASE ABILITY OF PENAEUS CHINENSIS

1996年5月24日—6月14日,8月1—19日,分别在青岛的两个养殖场采集海捕产卵后中国对虾亲虾和养殖中国对虾,采用人工添加氨氮并检测对虾与抗菌有关因子的活力的方法,进行氨氮对中国对虾抗病力影响的实验。结果表明,在氨氮浓度较高的实验组,对虾血细胞数目减少,其结构也有变化;酚氧化酶、超氧化物歧化酶和过氧化物酶活力,以及溶菌和抗菌活力都较对照组有明显下降;对病原菌的易感性明显提高。氨氮可降低中国对虾与抗病力有关的酶活力,从而提高中国对虾对病原体的易感性,增加发生疾病的可能性。

This article is concerned with how ammonia affects anti-disease ability of Penaeus chinensis and how it induces shrimp diseases. Tests were carried out in the Cultivation Bullding of Institute of Oceanology. From May 24 to June 14 and from Aug. 1 to Aug. 19 in 1996; wild parent P. chinensis which had hatched (bought from Prawn Farm of Shangma Town, Chengyang District Qingdao) and cultured P. chinensis (bought from Prawn Farm of Beisuo Village, Fengcheng Town, Jimo City) were used as test materials. Two ponds were chosen for testing and control samples, respectively, in each of which the same number of shrimps were reared. Except that fixed ammonium chloride was and into the test pond after renewing saltwater (100%) every day, other culture conditions, such as aeration, temperature and amount of diers, were maintained the same way in the two ponds.Water was changed at 08.00 am and diets were added twice every day. Physiochemical and microbiological factors, including ammonia-N, dissolved oxygen (DO), chemical oxygen demand (COD), pH, salinity, temperature, total heterotrophic basteria and Vibrio sp., were examined regulary.After about 20 days, the blood of shrimps was taken out or the muscle of shrimps was mixed as materials for eash examination; haemocyte number and structure changes of the two group shrimps were compared by hemocytometer and TEM, some enzyme activities relating to antidisease ability were measured by spectrophotometer and susceptibilities to Vibrio sp. were tested by injecting shrimps with Vibriosp.The results show that the haemocyte number of the test shrimps decreased more rapidly than the control and changes in haemocyte structure of the test shrimps occurred, phenoloxidase (PO),superoxide dismutase (SOD), peroxidase (POD), bacteriolytic and antibacterial activities of the test sample decreased by 19.1%, 15.1%, 21.4%, 12.5% and 36.6% more than the control one,respectively.In addition, the test group had higher susceptibilities to pathogenic bactoria Vibrio sp.than the control one.In conclusion ammonia-N can reduce enzyme activities of P. chinensis relating to anti-disease ability, increase its susceptibility to pathogen, and make it easy for diseases to occur.