Complete developmental cycle of Myxobolus pseudodispar (Gorbunova) (Myxosporea: Myxobolidae)

Myxobolus pseudodispar (Gorbunova) is a common parasite of the muscle of roach, Rutilus rutilus L., whereas its actinosporean development occurs in two oligochaete alternate hosts. This paper reports the complete developmental cycle of this parasite in the oligochaete alternate host Tubifex tubifex and the roach. In laboratory experiments, parasite-free T. tubifex specimens were infected by myxospores of M. pseudodispar collected from roach in Lake Balaton. Parasite-free roach fingerlings were infected with floating triactinospores (TAMs) released from oligochaetes on day 69 after challenge. Young plasmodia and spores in roach were first recorded on day 80 post-exposure (p.e.). Myxospores collected from experimentally infected roach initiated a new development in T. tubifex and the resulting TAMs infected roach. No infection of roach resulted from feeding oligochaetes containing mature triactinospores.     

Tubifex production using agro-industrial wastes and raw cattle dung

ABSTRACT

Tubifex (Tubifex tubifex) was cultured in captivity using three different wastes: rice mill sludge (RMS), dairy sludge (DS), and raw cattle dung (RCD). Three experiments were conducted: 10, 20, and 30 days. A total of 100 g of tubifex at 62.5 g m^?2 was inoculated in 1.6 m² fiberglass-reinforced plastic tanks. Comparing all production parameters, RMS > DS > RCD. Growth rate (g m^?2 d^?1) did not differ among durations. RMS- and DS-fed tubifex contained higher protein and fat than RCD-fed tubifex. Efficiency on production of g tubifex per kg of waste material was highest at 10 days, declining with time for all waste materials. This experiment suggests that RMS and DS are effective wastes for tubifex culture, with total production increasing with no reduction in growth rate through 30 days, but with efficiency declining after 10 days.     

Migration and Distribution Rules of Tubifex in Filtration

The rules of migration and distribution regulation of tubifex in filtration were studied in the pilot system. Meanwhile, the influences of filtration rate, filtration cycle and backwashing on the worm’s migration and distribution in filtraion were discussed. The results showed that both the worm’s length and the particle size of filter media had obvious effects on migration and distribution: the smaller the worm’s length and the larger the particle size of filter media were, the stronger the worm’s migration capacity was. The filtration rate was the main migration power of tubifex in filtration, which meant high filtration rate could result in the worm’s leakage risk. Prolonging filtration cycle promoted migration, thus it is beneficial to control tubifex leakage risk that shortening filtration cycle. The remove of tubifex in a real sense can be realized by backwashing. And the stronger the backwashing intensity is, the better the removal efficiency is. Based on the experimental results, to control the worm’s leakage risk effectively, filtration rate and cycle would be lower than 9.4 m/h and 12 h, respectively. Backwashing intensity would be controlled about 25 L/s·m2, at which the obtained tubifex removal efficiency was 97.7%.     

颤蚓对水田沉积物颗粒垂直运移的生物扰动效应

[目的]研究颤蚓扰动对水田沉积物颗粒垂直运移的作用,探讨底栖环节动物在水层-底栖界面耦合过程中的生物扰动作用和机制。[方法]以化学性质稳定的玻璃珠作为示踪颗粒,对比分析水田沉积物颗粒垂直运移在有/无颤蚓活动时的差异。[结果]颤蚓扰动10 d后,沉积物表层示踪颗粒有41.3%向下迁移,最大迁移深度为9.4 cm,垂直迁移率为1.370×10-3/（g.cm2.d）。6 cm深处的示踪颗粒分别有25.8%和17.3%在扰动后向上和向下迁移,向上和向下最大迁移距离分别为5.2 cm和2.7 cm,垂直向上和向下迁移率分别为8.557×10-4/（g.cm2.d）和5.738×10-4/（g.cm2.d）。[结论]颤蚓通过自身的活动,使水田表层和深层沉积物颗粒在垂直方向上发生运移,改变了沉积环境。     

4种常用水产药物对水蚯蚓的急性毒性实验

采用曝气自来水,在水温（20±1）℃,pH值6.8～7.1条件下,应用高锰酸钾、甲醛、聚维酮碘和溴氰萄酯4种常用水产药物对水蚯蚓进行急性毒性试验。结果表明：4种药物对水蚯蚓的半致死浓度（LC_（50））依次为：高锰酸钾〉溴氰菊酯〉聚维酮碘〉甲醛。安全浓度（SC）分别为0.02、0.93、1.50和4.07 mg/L。4种药物均为低毒药物,在水蚯蚓养殖中使用是安全可靠的。