Mouritsen K N, Elkjær C K
Department of Biology, Aquatic Biology, Aarhus University, Ole Worms Allé 1, 8000Aarhus C, Denmark.
J Helminthol. 2020 Apr 2;94:e139. doi: 10.1017/S0022149X20000243.
In a range of trematode species, specific members of the parthenitae colony infecting the molluscan first intermediate host appear specialized for defence against co-infecting species. The evolution of such division of labour requires that co-infection entails fitness costs. Yet, this premise has very rarely been tested in species showing division of labour. Using Himasthla elongata (Himasthlidae) and Renicola roscovita (Renicolidae) infecting periwinkles Littorina littorea as study system, we show that the size of emerged cercariae is markedly reduced in both parasite species when competing over host resources. Cercarial longevity, on the other hand, is negatively influenced by competition only in R. roscovita. Season, which may impact the nutritional state of the host, also affects cercarial size, but only in H. elongata. Hence, our study underlines that cercarial quality is, indeed, compromised by competition, not only in the inferior R. roscovita (no division of labour) but also in the competitively superior H. elongata (division of labour).
在一系列吸虫物种中，感染软体动物第一中间宿主的胞蚴群体中的特定成员似乎专门用于抵御共同感染的物种。这种分工的进化要求共同感染会带来适应性成本。然而，这一前提在表现出分工的物种中很少得到验证。以感染滨螺（Littorina littorea）的长形希马斯吸虫（Himasthla elongata，希马斯吸虫科）和罗斯科夫肾吸虫（Renicola roscovita，肾吸虫科）作为研究系统，我们发现，当两种寄生虫在宿主资源上竞争时，两种寄生虫逸出的尾蚴大小均显著减小。另一方面，尾蚴寿命仅在罗斯科夫肾吸虫中受到竞争的负面影响。季节可能会影响宿主的营养状况，也会影响尾蚴大小，但仅对长形希马斯吸虫有影响。因此，我们的研究强调，尾蚴质量确实会因竞争而受损，不仅在处于劣势的罗斯科夫肾吸虫（无分工）中如此，在竞争优势较强的长形希马斯吸虫（有分工）中也是如此。
