Institute of Evolution, Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3JT, UK.
Proc Biol Sci. 2011 Aug 22;278(1717):2429-36. doi: 10.1098/rspb.2010.2457. Epub 2011 Jan 5.
Circadian biology assumes that biological rhythms maximize fitness by enabling organisms to coordinate with their environment. Despite circadian clocks being such a widespread phenomenon, demonstrating the fitness benefits of temporal coordination is challenging and such studies are rare. Here, we tested the consequences--for parasites--of being temporally mismatched to host circadian rhythms using the rodent malaria parasite, Plasmodium chabaudi. The cyclical nature of malaria infections is well known, as the cell cycles across parasite species last a multiple of approximately 24 h, but the evolutionary explanations for periodicity are poorly understood. We demonstrate that perturbation of parasite rhythms results in a twofold cost to the production of replicating and transmission stages. Thus, synchronization with host rhythms influences in-host survival and between-host transmission potential, revealing a role for circadian rhythms in the evolution of host-parasite interactions. More generally, our results provide a demonstration of the adaptive value of circadian rhythms and the utility of using an evolutionary framework to understand parasite traits.
昼夜节律生物学假设，生物节律通过使生物体与环境协调一致，从而最大限度地提高适应性。尽管昼夜节律是一种广泛存在的现象，但证明时间协调的适应性益处具有挑战性，此类研究也很少见。在这里，我们使用啮齿动物疟原虫 Plasmodium chabaudi 测试了与宿主昼夜节律时间不匹配对寄生虫的后果。疟疾感染的周期性是众所周知的，因为寄生虫物种的细胞周期持续大约 24 小时的倍数，但周期性的进化解释还知之甚少。我们证明，寄生虫节律的扰乱会导致复制和传播阶段的产生成本增加一倍。因此，与宿主节律的同步会影响寄生虫在体内的存活和在宿主之间的传播潜力，这揭示了昼夜节律在宿主-寄生虫相互作用进化中的作用。更普遍地说，我们的研究结果证明了昼夜节律的适应性价值，以及使用进化框架来理解寄生虫特征的实用性。
