Shirakashi Sho, Goater Cameron P
Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4.
J Parasitol. 2002 Dec;88(6):1071-4. doi: 10.1645/0022-3395(2002)088[1071:IDAOMP]2.0.CO;2.
We examined the relationship between the numbers of brain-encysting trematodes (Ornithodiplostomum ptychocheilus) and the magnitude of altered behaviors in fathead minnows (Pimephales promelas). Because cysts develop within a brain region that integrates visual stimuli with motor response. we evaluated the standard optomotor response (OMR). Monitoring this task involved recording the time minnows spent following a spinning drum, on which alternating black and white stripes had been painted. Minnows were exposed to 0, 5, 20, 120, and 300 cercariae and then their OMR was evaluated at 2-wk postinfection. Surprisingly, only minnows that had high numbers of parasites (155 +/- 31 worms/fish) or low numbers of parasites (3 +/- 3 worms/ fish) differed significantly in their optomotor performance compared with controls. Reduced OMR of heavily infected minnows was positively correlated with reduction in minnow activity. In contrast, reduced OMR in lightly infected minnows was independent of host activity and was likely associated with the rapid development of parasite larvae within the optic tecta. The nonlinear relationship between parasite intensity and effect on host behavior was consistent with an earlier study, but the underlying mechanisms producing this pattern are unknown.
我们研究了脑内寄生吸虫（褶盘双腔吸虫）的数量与黑头呆鱼行为改变程度之间的关系。由于囊肿在一个将视觉刺激与运动反应整合的脑区中形成，我们评估了标准视动反应（OMR）。监测这项任务包括记录呆鱼跟随一个旋转鼓（上面绘制了黑白交替条纹）所花费的时间。将呆鱼暴露于0、5、20、120和300尾尾蚴中，然后在感染后2周评估它们的OMR。令人惊讶的是，与对照组相比，只有寄生虫数量多（155±31条虫/鱼）或寄生虫数量少（3±3条虫/鱼）的呆鱼在视动表现上有显著差异。重度感染呆鱼的OMR降低与呆鱼活动减少呈正相关。相比之下，轻度感染呆鱼的OMR降低与宿主活动无关，可能与视顶盖内寄生虫幼虫的快速发育有关。寄生虫强度与对宿主行为影响之间的非线性关系与早期研究一致，但产生这种模式的潜在机制尚不清楚。
