槟榔、川楝子复方中草药对大黄鱼4种酶活性的影响及对刺激隐核虫的杀灭效果分析

摘要

Cryptocarioniasis, which is caused by Cryptography irritans, is difficult to control in cultured large yellow croaker,Larimichthys crocea and dozens of other marine fish species and is seriously threatening devel-opment of the aquaculture industry. To investigate the effects of the Chinese herbal compound (HD-2) [Areca catechu L,Melia toosendan Sieb.et Zucc,Dryopteris crassirhizoma,Folium isatidis, and Andrographis paniculata (Burm. f.) Nees] for treating cryptocarioniasis,L.crocea were collected and fed different doses of HD-2 to compare changes in non-specific immune indices, such as lysozyme (LZM), total superoxide dismutase(T-SOD), alkaline phosphatase (AKP), and acidic phosphatase (ACP) activities. The results showed that HD-2 promoted LZM, T-SOD, AKP, and ACP activities, and maximum activities were observed 14–21 d after feeding 2% HD-2. No C. irritanstheronts were killed in 50 mg/L HD-2 within 4 hin vitro. However, 20%, 54%, and 89% of the theronts were killed at concentrations of 80 mg/L, 100 mg/L, and 200 mg/L HD-2, respectively; all theronts were killed by 400 mg/L HD-2. The median lethal concentration for 50% (LC50) of the theronts was 109 mg/L. A 15-d indoor therapeutic experiment was performed in which fish were assigned randomly into groups A–C and a control. Fish in group A had a survival rate of 50% after being fed 20 g/kg HD-2 in feed and dipped in a 100 mg/L HD-2 bath. Fish in group B had a survival rate of 50.67% after being fed 20 g/kg HD-2 in feed and dipped in a 50 mg/L HD-2 bath. Fish in group C achieved a survival rate of 42.67% after being fed 20 g/kg HD-2 in feed. The survival rates of the three treatment groups were significantly higher than that of the control group (2.67%). The number of trophontson the pectoral fins ofL. croceawas significantly lower than that in the control group. The number of trophonts onL. croceagill filaments declined during the three treatments. In contrast, the number of trophonts in the control group increased significantly, where as the number of tomonts in the treated groups decreased signifi-cantly. The numbers of tomonts in groups A, B, and C decreased by 100%, 91.1%, and 77.7%, respectively, on day 12 and were significantly different from those in the control group. In conclusion, simultaneous oral administra-tion and a medicated bath in HD-2 was the most efficacious treatment for cryptocarioniasis. The 2% HD-2 oral treatment added to feed for 6–14 d is recommended to guarantee higher survival rates of L. crocea based on availability and cost considerations. These results provide a theoretical reference and technical support for pre-venting and controlling cryptocarioniasis, and will be useful for fish culture in future.%海水小瓜虫病是养殖大黄鱼(Larimichthys crocea)和数十种海水鱼类较难控制的主要疾病,它是由刺激隐核虫(Cryptography irritans)感染引发,严重威胁鱼类养殖产业的健康发展.本研究利用复方中草药"HD-2"(槟榔、川楝子、绵马贯众、大青叶、穿心莲等以一定比例混合,超微粉碎经过200目过筛后收集粉末)投喂大黄鱼,研究大黄鱼溶菌酶(LZM)、总超氧化物歧化酶(T-SOD)、碱性磷酸酶(AKP)、酸性磷酸酶(ACP)等非特异性免疫指标变化和不同用药方式对刺激隐核虫的杀灭效果.结果显示,口服"HD-2"可以促进鱼体LZM、T-SOD、AKP、ACP活性升高,以添加2%中草药组在提高4种酶活性方面作用显著,投喂后第14~21天酶活性最高."HD-2"对体外刺激隐核虫幼虫的杀灭实验证实:4 h内在50 mg/L浓度下对幼虫没有杀伤作用,80 mg/L、100 mg/L、200 mg/L浓度分别可以杀死20%、54%、89%的幼虫,400 mg/L浓度下幼虫被全部杀死,幼虫4 h半致死浓度为109 mg/L.在室内为期15 d的大黄鱼小瓜虫病治疗实验中,A组按20 g/kg添加"HD-2"药物口服,同时按100 mg/L浓度药浴,存活率为50%;B组按20 g/kg添加药物口服,同时按50 mg/L浓度药浴,存活率50.67%;C组,在无药浴情况下,仅按20 g/kg添加药物口服,存活率为42.67%;A、B、C组存活率均显著高于对照组存活率2.67%(P<0.05).此外,A、B、C 3组中,大黄鱼胸鳍上白点数量明显少于对照组;同时,3个组的大黄鱼鳃丝上隐核虫数量均呈显著下降趋势(P<0.05),实验结束时几乎观察不到虫体;而对照组大黄鱼鳃丝上隐核虫数量明显上升.实验过程中A、B、C 3组大黄鱼释放到体外的包囊数量明显下降,第12天时其包囊数量分别下降100%、91.1%、77.7%,与对照组差异极显著(P<0.01).综上所述,口服和药浴同时用药具有最佳效果,仅口服中草药亦能达到良好治疗效果.从实用性和成本考虑,建议仅进行口服处理,即能保障大黄鱼较高成活率,中草药添加量为2%,投喂时间为6~14 d.该结果为防控鱼类小瓜虫病提供了理论参考和技术支撑,在养殖生产中将具有良好的应用前景.