Studies on the obstracting mechanism of Protozoa in Mass Culture of Food Organisms and its Control

1.罗氏臂尾轮虫规模化养殖原生动物区系的演替：纤毛虫、凡纳游毛虫和尾丝虫。在正常水平的1/2至2/1的口粮中占主导地位。原生动物在食物网中的作用：分离和人工培养较大的纤毛虫，作为与海洋轮虫竞争的代表原生动物。当接种到轮虫培养物中时，超过1000个细胞/毫升的繁殖阻碍了轮虫的生长。在轮虫培养中纤毛虫占主导地位的机理通过实验推测如下：(1)在轮虫培养的滞后期，纤毛虫可以摄食因轮虫过度摄食而死亡的附着细菌的藻类，但纤毛虫不能利用活的代数。(2)在对数生长期，作为纤毛虫优良食物的轮虫粪便产量较高。然而，轮虫的捕食性竞争了它。(3)在静止期，由于有机物积累过多，轮虫活性降低，细菌产生旺盛，纤毛虫“享受”。建立了轮虫水箱中出现的杀灭轮虫原生动物的Tanka大规模培养技术。对轮虫的24小时半数致死量仅为10^4~10^5个/ml。经透射电子显微镜等检测，鉴定为马利氏氧化杆菌。这是首次发现对海洋轮虫致死的原生动物。Sephadex色谱柱提取的特定甲醇组分具有较强的毒性。用抗生素控制原生动物的可能性用HPLC.5检测轮虫养殖水中4种抗生素的残留。公布了两年的实验结果。

1. Succession of protozoal fauna in mass culture of the marine rotifer Brachionus rotundiformis : Ciliates, Euplotes vannus and Uronema sp. were dominant in food rations from 1/2 to 2/1 of normal level.2. Function of Protozoa in food web :The larger ciliates E.vannus was isolated and artificially cultured as the representative protozoon which competes with the marine rotifer. The propagation exceeding 1000 cells/ml obstracted the growth of the rotifer when inoculated into rotifer cultures. The mechamism that the ciliate dominates in rotifer culture was postulated from experiments using ^<15>N tracer as follows.(1) In lag phase of rotifer culture, the ciliate can fed those dead and bacteria-attached algae which exist as the result of excessive feeding for the rotifer, though the ciliates can not utilize live algea. (2) In log phase, rotifer faeces, which are excellent food for the ciliate, produced enough. Scatrophagy of the rotifer, however, competes it. (3) In stationary phase, rotifer activity comes to decrease because of too much accumulation of organic substances, which makes bacteria production vigorously and the ciliate "enjoy" it.3. Killing protozoa isolated from a mass culture tankA mass culture technique of the killing Heliozoa which appeared in a rotifer tank was established. The 24hrs'LD_<50> was only 10^4-10^5 cells/ml to the rotifer. From inspections using TEM etc, it was identified as Oxnerella maritima. It is the first record of lethal Protozoa to marine rotifer. A specific fraction of MeOH extract by the Sephadex colum had strong lethality.4. The probability of Protozoa-control by antibioticsThe remaining of four antibiotics in rotifer culturing water was examined by HPLC.5. PublicationThe results of two years'experiment are published.