Nelson Felicity B L, Brown Gregory P, Dubey Sylvain, Shine Richard
School of Biological Sciences A08, University of Sydney, NSW 2006, Australia.
J Parasitol. 2015 Jun;101(3):290-6. doi: 10.1645/14-657.1. Epub 2015 Feb 9.
Biological invasions can bring both the invader and native taxa into contact with novel parasites. As cane toads ( Rhinella marina ) have spread through Australia, they have encountered lungworms (Rhabdias hylae) that occur in native frogs. Field surveys suggest that these lungworms have not host-switched to toads. In our laboratory studies, R. hylae infected cane toads as readily as it infected native frogs, but failed to reach the lungs of the novel host (i.e., were killed by the toads' immune response). Plausibly, then, R. hylae might reduce the viability both of their native hosts (frogs, that can exhibit high parasite burdens) and cane toads (that must deal with infective larvae traveling through the host body). Our laboratory trials suggest, however, that the impacts of the parasite on infected anuran hosts (both frogs and toads) were minimal, with no significant decrements to host survival, activity, growth, or locomotor performance. Ironically, the lack of impact of the parasite on its native hosts appears to be an outcome of co-evolution (frogs tolerate the lungworm), whereas the lack of impact on the novel host is due to a lack of co-evolution (toads can recognize and eliminate the lungworm).
生物入侵会使入侵物种和本地物种接触到新的寄生虫。随着蔗蟾（海蟾蜍）在澳大利亚扩散，它们遇到了本地青蛙体内的肺线虫（蛙杆线虫）。野外调查表明，这些肺线虫并未转换宿主感染蔗蟾。在我们的实验室研究中，蛙杆线虫感染蔗蟾的难易程度与感染本地青蛙相同，但无法到达新宿主的肺部（即被蔗蟾的免疫反应杀死）。那么，蛙杆线虫可能会降低其本地宿主（青蛙，可能携带大量寄生虫）和蔗蟾（必须应对穿过宿主体内的感染性幼虫）的生存能力。然而，我们的实验室试验表明，这种寄生虫对受感染的无尾目宿主（青蛙和蔗蟾）的影响微乎其微，对宿主的生存、活动、生长或运动表现没有显著影响。具有讽刺意味的是，寄生虫对其本地宿主缺乏影响似乎是共同进化的结果（青蛙耐受肺线虫），而对新宿主缺乏影响则是由于缺乏共同进化（蔗蟾能够识别并清除肺线虫）。
