Gendron Andrée D, Marcogliese David J
Aquatic Contaminants Research Division, Water Science and Technology Directorate, Environment Canada, St. Lawrence Centre, 105 McGill, 7th Floor, Montreal, Quebec H2Y 2E7, Canada.
Int J Parasitol Parasites Wildl. 2017 Apr 29;6(3):402-411. doi: 10.1016/j.ijppaw.2017.04.002. eCollection 2017 Dec.
As they integrate into recipient food webs, invasive exotic species may influence the population dynamics of native parasites. Here we assess the potential impact of the Eurasian round goby () on the abundance of eyeflukes of the genus , which are common parasites in fishes of the St. Lawrence River (Canada). Analyses of data collected over nearly two decades revealed that the infection levels in three native fish [spottail shiner (), golden shiner () yellow perch ()] declined sharply throughout the St. Lawrence River after the introduction of the goby. At two sites where data were collected at regular time intervals, declines of spp. in spottail shiners occurred within two years of the goby's first recorded appearance, with prevalence dropping as much as 77-80% between pre-invasion and post-invasion periods. Furthermore, in localities where gobies remained scarce, infection in native species did not change significantly over time. Altogether, these observations suggest that gobies play a role in the eyefluke collapse. The decline in populations of the main definitive host (ring-billed gulls, ) and changes in hydrology during periods of parasite recruitment were not strongly supported as alternate explanations for this phenomenon. Since other snail-transmitted trematodes with similar life cycles to spp. did not show the same decreasing pattern, we conclude that eyeflukes did not decline as a result of snail depletion due to goby predation. Rather, we suggest that gobies acted as decoys, diluting the infection. As spp. occurred at lower abundance in gobies than in native fish hosts, the replacement of native fish with exotic gobies in the diet of gulls might have played a part in reducing parasite transmission. In contrast to the typically negative impact of invasions, the goby-induced decline of this pathogen may have beneficial effects for native fishes.
随着外来入侵物种融入受体食物网，它们可能会影响本地寄生虫的种群动态。在此，我们评估了欧亚圆腹雅罗鱼（Neogobius melanostomus）对复口吸虫属（Diplostomum）眼吸虫丰度的潜在影响，复口吸虫是加拿大圣劳伦斯河鱼类中常见的寄生虫。对近二十年来收集的数据进行分析后发现，在雅罗鱼引入后，圣劳伦斯河下游三种本地鱼类（细纹鳟鱼（Notropis hudsonius）、金色闪光鱼（Notemigonus crysoleucas）、黄鲈（Perca flavescens））的感染水平急剧下降。在两个定期收集数据的地点，细纹鳟鱼体内复口吸虫属物种的数量在雅罗鱼首次出现后的两年内就开始下降，入侵前和入侵后的流行率下降了77%-80%。此外，在雅罗鱼数量仍然稀少的地区，本地物种的感染情况并未随时间发生显著变化。总体而言，这些观察结果表明，雅罗鱼在眼吸虫数量崩溃中起到了作用。主要终末宿主（环嘴鸥，Larus delawarensis）数量的下降以及寄生虫繁殖期水文条件的变化，作为对这一现象的替代解释，并没有得到有力支持。由于其他具有与复口吸虫属相似生命周期的蜗牛传播吸虫并未呈现相同的下降模式，我们得出结论，眼吸虫数量的下降并非由于雅罗鱼捕食导致蜗牛数量减少所致。相反，我们认为雅罗鱼起到了诱饵的作用，稀释了感染。由于复口吸虫属在雅罗鱼体内的丰度低于本地鱼类宿主，鸥类饮食中本地鱼类被外来雅罗鱼取代可能在减少寄生虫传播方面起到了一定作用。与入侵通常带来的负面影响相反，雅罗鱼导致这种病原体数量下降可能对本地鱼类具有有益影响。
