Shaw J C, Korzan W J, Carpenter R E, Kuris A M, Lafferty K D, Summers C H, Øverli Ø
Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106-7130, USA.
Proc Biol Sci. 2009 Mar 22;276(1659):1137-46. doi: 10.1098/rspb.2008.1597.
California killifish (Fundulus parvipinnis) infected with the brain-encysting trematode Euhaplorchis californiensis display conspicuous swimming behaviours rendering them more susceptible to predation by avian final hosts. Heavily infected killifish grow and reproduce normally, despite having thousands of cysts inside their braincases. This suggests that E. californiensis affects only specific locomotory behaviours. We hypothesised that changes in the serotonin and dopamine metabolism, essential for controlling locomotion and arousal may underlie this behaviour modification. We employed micropunch dissection and HPLC to analyse monoamine and monoamine metabolite concentrations in the brain regions of uninfected and experimentally infected fish. The parasites exerted density-dependent changes in monoaminergic activity distinct from those exhibited by fish subjected to stress. Specifically, E. californiensis inhibited a normally occurring, stress-induced elevation of serotonergic metabolism in the raphae nuclei. This effect was particularly evident in the experimentally infected fish, whose low-density infections were concentrated on the brainstem. Furthermore, high E. californiensis density was associated with increased dopaminergic activity in the hypothalamus and decreased serotonergic activity in the hippocampus. In conclusion, the altered monoaminergic metabolism may explain behavioural differences leading to increased predation of the infected killifish by their final host predators.
感染了寄生于脑部的吸虫加州真雀鲷吸虫(Euhaplorchis californiensis)的加州鳉鱼(Fundulus parvipinnis)表现出明显的游动行为,这使它们更容易被鸟类终末宿主捕食。尽管脑壳内有数千个囊肿,但重度感染的鳉鱼仍能正常生长和繁殖。这表明加州真雀鲷吸虫仅影响特定的运动行为。我们推测,控制运动和觉醒所必需的血清素和多巴胺代谢变化可能是这种行为改变的基础。我们采用微量打孔解剖和高效液相色谱法分析未感染和实验感染鱼类脑区中的单胺和单胺代谢物浓度。寄生虫引起的单胺能活性变化与密度有关,这与遭受应激的鱼类表现出的变化不同。具体而言,加州真雀鲷吸虫抑制了中缝核中正常发生的、由应激诱导的血清素代谢升高。这种效应在实验感染的鱼类中尤为明显,其低密度感染集中在脑干。此外,高浓度的加州真雀鲷吸虫与下丘脑多巴胺能活性增加以及海马体血清素能活性降低有关。总之,单胺能代谢的改变可能解释了导致感染鳉鱼被其终末宿主捕食增加的行为差异。