Münderle M, Sures B, Taraschewski H
Zoologisches Institut, Okologie/Parasitologie, Universität Karlsruhe, Kornblumenstrasse 13, 76131 Karlsruhe, Germany.
Dis Aquat Organ. 2004 Aug 9;60(2):133-9. doi: 10.3354/dao060133.
We investigated the swimming activity of 70 European eels Anguilla anguilla in relation to natural infection with 2 parasite species: the eel-specific swimbladder nematode Anguillicola crassus and the non-specific skin and gill protozoan Ichthyophthirius multifiliis. We measured how long individual eels exposed to a water current in a swimming channel with a steady-stream profile could withstand the water current. The parasites affected the swimming behaviour of eels in different ways. The maximum period of time the fish were able to swim against the current was not correlated with infection by A. crassus. In contrast, infection with I. multifiliis reduced the swimming time. The protozoan has a higher pathogenicity than the swimbladder nematode, at least in closed systems, where I. multifiliis is able to spread within a few days. Reduction in swimming capacity after infection with the ciliate averaged 47 % compared to capacity prior to infection. Thus, our results do not support the previously suggested strong negative relation between swimming activity of eels and intensity of A. crassus infection, at least in the short-term. However, there are indications in the literature that the pathological effects of A. crassus on the eel swimmbladder may involve a higher energy demand, possibly manifested in a prolonged spawning migration. As a result, eels heavily infected with this parasite may arrive too late at the spawning site to participate in mating. This could ensure a selection of 'good genes'.
我们研究了70条欧洲鳗鲡（Anguilla anguilla）的游泳活动，以及它们与两种寄生虫自然感染之间的关系：鳗鲡特有的鳔线虫（Anguillicola crassus）和非特异性的皮肤及鳃部原生动物多子小瓜虫（Ichthyophthirius multifiliis）。我们测量了个体鳗鲡在具有稳定水流剖面的游泳通道中暴露于水流时，能够承受水流的时间长度。这些寄生虫以不同方式影响鳗鲡的游泳行为。鱼类逆流游泳的最长时间与粗厚鳗线虫感染无关。相比之下，多子小瓜虫感染会缩短游泳时间。这种原生动物的致病性高于鳔线虫，至少在封闭系统中是这样，在封闭系统中多子小瓜虫能够在几天内传播。与感染前的能力相比，感染纤毛虫后游泳能力的下降平均为47%。因此，我们的结果至少在短期内不支持先前提出的鳗鲡游泳活动与粗厚鳗线虫感染强度之间强烈的负相关关系。然而，文献中有迹象表明，粗厚鳗线虫对鳗鲡鳔的病理影响可能涉及更高的能量需求，这可能表现为产卵洄游时间延长。结果，感染这种寄生虫严重的鳗鲡可能到达产卵地太晚而无法参与交配。这可以确保对“优良基因”的选择。
