Center for Pathophysiology, Infectiology & Immunology, Department of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria.
Wien Klin Wochenschr. 2010 Oct;122 Suppl 3:91-3. doi: 10.1007/s00508-010-1444-8.
Numerous specimens of the native, intestinal digenean fluke Pleurogenoides sp. (Lecithodendriidae, Plagiorchiida), a genus known for the simultaneous co-existence of genuine adults and progenetic, adult-like metacercaria, were found by chance parasitizing in the oesophagus of a recently imported, tropical Bristly Bush Viper (Atheris hispida). The snake had before been force-fed with native water frogs, the assumed definitive host of these flukes. Hence water frogs act as the second intermediate host or as a paratenic host for Pleurogenoides flukes, as they must house progenetic fluke larvae, which develop to genuine adults when transmitted to an appropriate consecutive host, the ancestral definitive host, a reptile. The European Pleurogenoides fluke species seem to display a facultative life-cycle diversification, they can adjust their life-history strategy according to their immediate transmission opportunities. This phenotypic plasticity allows the parasite to respond quickly to any changes in the abundance of a host; usually this biological oddity results in a life-cycle truncation by the elimination of the definitive host.
偶然发现，大量的本地肠内双腔吸虫 Pleurogenoides sp.（Leci thodendriidae，Plagiorchiida）标本寄生在一条最近进口的热带刺鳞蛇（Atheris hispida）的食道中。该蛇曾被强制喂食本地水蛙，而这些吸虫的终末宿主被认为就是水蛙。因此，水蛙既是第二中间宿主，也是双腔吸虫的副宿主，因为水蛙必须容纳幼虫，这些幼虫在传播到合适的连续宿主，即祖先的终末宿主爬行动物时，会发育成真正的成虫。欧洲双腔吸虫物种似乎表现出一种兼性生命周期多样化，它们可以根据自身的传播机会来调整其生活史策略。这种表型可塑性使寄生虫能够快速应对宿主丰度的任何变化；通常情况下，这种生物奇异现象会导致生命周期缩短，因为终末宿主被消除。
