沼蛤(Limnoperna fortunei)幼虫的附着行为特性

Experimental study of attachment characteristics of golden mussel larvae

沼蛤(Limnoperna fortunei Dunker,1857),俗称淡水壳菜,是一种扩散能力与适应能力都较强的入侵性底栖动物,它对自然环境与输水工程的侵入和大规模附着,不仅会破坏当地的生物群落结构,而且沼蛤成贝在工程内稳定附着后难以去除,造成重大工程危害。通过试验研究沼蛤幼虫的附着行为特性,并利用该特性对原水中的幼虫进行吸引附着处理,以减少幼虫进入工程造成污损附着。选用前期研究推荐的沼蛤幼虫喜好附着的黄麻材料制成的附着排作为试验材料,设置5组附着排长度工况:1,3,5,6,8 m,在5组流量工况:3.1,5.7,6.7,9.6,12.1 L/s下开展试验,研究不同附着排长度和流量条件下沼蛤幼虫的附着行为,以便优选出吸附幼虫的最佳条件。试验结果表明:(1)黄麻材料的吸附效果与附着排长度呈正相关关系,材料长度为3—5m时,吸附率即可达到50%;材料长度为6—8 m时,平均效果为62—76%,最佳吸附率可达93%;(2)流量过大会降低幼虫吸附效果,吸附也更不稳定;(3)幼虫发育先后经历D型幼虫、前期壳顶幼虫、后期壳顶幼虫、踯行期4个时期,吸附材料对后期壳顶和踯行期幼虫的吸附效果较前期壳顶幼虫更好;(4)附着材料密集布置于较短的长度内比稀疏布置于较长的长度内更有利于提高附着效果。

Golden mussel （Limnoperna fortunei Dunker, 1857） is an invasive benthic macroinvertebrate species with dispersal ability and strong environmental adaptability. It is native to southern China, and its distribution has expanded to northern China, southeastern Asia, and many areas in South America. Its invasion and dense attachment on natural environments and water transfer works not only causes damage to the local bio-community, but also leads to high risk to the works owing to difficulties in removing adult mussels due to their tight attachment to the surface. Consequently, prevention of the entry of golden mussel larvae into the water transfer works has been considered as the most efficient means of avoiding invasion of this species. This experiment studied the attachment characteristics of golden mussel larvae, and proposed measures for attracting the larvae in raw water to attach onto suitable materials. This reduced the density of golden mussel larvae entering into the water transfer works and therefore the attachment density of adult mussels on the water transfer pipelines. Hessian material, which the results of our previous study indicated as a suitable material for golden mussel attachment, was selected and set up into attachment plates for （ 1, 3, 5, 6 and 8 m） and five different discharges （3.1, 5.7, the species. Five different sets of attachment plate lengths 6.7, 9.6, and 12.1 L/s） were tested to study the influencesof the length of attachment material and flow discharge on attaching behaviors of golden mussel larvae. A microscope was applied to observe the larvae with assistance of the SmartV Camera image acquisition system to capture images. The images analysis software MIVNT was used to measure the sizes of the larvae in the captured images. Variation of larval density upstream and downstream of the attachment plates was analyzed and used to indicate attachment efficiency. Optimum conditions of the attachment material length and flow discharge were then determined that would attract larvae to the maximum extent. The experimental results indicated that （ 1 ） the attachment rate of golden mussel larvae on the hessian material was positively related to the attachment plate length. Attachment rate reached 50% when the attachment plate length was 3--5 m. The average attachment rate reached 62%--76%, with the highest rate being as high as 93% when plate length was 6--8 m; （2） the attachment rate of golden mussel larvae decreased with increase in flow discharge; （3） the attachment rate of pediveligers and plantigrade veligers on the material was much higher than that of umbonated veligers ; （4） dense arrangement of the hessian attachment plates at a short distance was more effective in improving the attachment efficiency than was sparse arrangement at a longer distance.