Ciliates represent an important trophic link between nanoplankton and mesoplankton. Many species acquire functional chloroplasts from photosynthetic prey, being thus mixotrophs. Little is known about which algae they exploit, and of the relevance of inorganic carbon assimilation to their metabolism. To get insights into these aspects, laboratory cultures of three mixotrophic Strombidium spp. were established and 35 photosynthetic algal species were tested as prey. The relative contributions of ingestion and photosynthesis to total carbon uptake were determined, and responses to prey starvation were studied. Ciliate growth was supported by algal species in the 2–12 μm size range, with cryptophytes and chlorophytes being the best prey types. Inorganic carbon incorporation was only quantitatively important when prey concentration was low (3–100 μgCL⁻¹), when it led to increased gross growth efficiencies. Chla specific inorganic carbon uptake rates were reduced by 60–90% compared to that of the photosynthetic prey. Inorganic carbon uptake alone could not sustain survival of cultures and ciliate populations declined by 25–30% during 5 days of starvation. The results suggest that mixotrophy in Strombidium spp. may substantially bolster the efficiency of trophic transfer when biomass of small primary producers is low.

中文翻译：

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混合营养型Strombidium spp的生理生态特征

纤毛虫是纳米浮游生物和中浮游生物之间重要的营养纽带。许多物种从光合作用的猎物获取功能性叶绿体，从而成为混合营养生物。关于它们利用哪种藻类以及无机碳同化与其代谢的相关性鲜为人知。为了深入了解这些方面，对三种混合营养型Strombidium进行了实验室培养spp。建立了35个光合藻类物种作为猎物。确定摄食和光合作用对总碳吸收的相对贡献，并研究对猎物饥饿的反应。纤毛虫的生长受到2–12μm大小范围内的藻类物种的支持，其中隐性植物和绿藻类是最好的猎物类型。无机碳掺入只有在猎物浓度较低时（3–100μgCL ^-1）才具有数量上的重要性，这会导致总生长效率提高。叶绿素一与光合作用的猎物相比，特定的无机碳吸收率降低了60–90％。单靠无机碳吸收并不能维持文化的生存，在饥饿的5天中纤毛虫种群下降了25-30％。结果表明Strombidium spp中的混合营养。小型初级生产者的生物量较低时，可大大提高营养传递的效率。