Institut de Ciències del Mar (ICM-CSIC), Passeig Marítim de la Barceloneta 37-49, 08003, Barcelona, Spain.
Department of Marine Sciences, University of Gothenburg, Box 461, SE-450 30, Göteborg, Sweden.
Microb Ecol. 2021 Aug;82(2):356-364. doi: 10.1007/s00248-020-01665-9. Epub 2021 Jan 18.
We have assessed the effect of copepod chemical cues on the diel feeding rhythms of heterotrophic and mixotrophic marine protists. All phagotrophic protists studied exhibited relatively high diurnal feeding rates. The magnitude of the diel feeding rhythm, expressed as the quotient of day and night ingestion rates, was inversely related to the time that phagotrophic protists were maintained in the laboratory in an environment without predators. In the case of the recently isolated ciliate Strombidium arenicola, the rhythm was lost after a few months. When challenged with chemical alarm signals (copepodamides) from the copepod Calanus finmarchicus at realistic concentrations (0.6-6 pM), S. arenicola partially re-established diurnal feeding. Conversely, the amplitude of the diel feeding rhythm for the ciliate Mesodinium rubrum was not affected by copepodamides, although the 24-h integrated food intake increased by approximately 23%. For the dinoflagellates Gyrodinium dominans and Karlodinium armiger, copepodamides significantly reduced the amplitude of their diel feeding rhythms; significant positive effects on total daily ingestion were only observed in G. dominans. Finally, the dinoflagellate Oxyrrhis marina, isolated >20 years ago, showed inconsistent responses to copepodamides, except for an average 6% increase in its total ingestion over 24 h. Our results demonstrate that the predation risk by copepods affects the diel feeding rhythm of marine protists and suggests a species-specific response to predation threats.
我们评估了桡足类化学信号对异养和混合营养海洋原生动物昼夜摄食节律的影响。所有研究的吞噬性原生动物都表现出相对较高的昼夜摄食率。昼夜摄食节律的幅度，以昼夜摄食率的商表示，与吞噬性原生动物在没有捕食者的环境中在实验室中维持的时间成反比。对于最近分离的纤毛虫 Strombidium arenicola，在几个月后失去了节律。当用桡足类 Calanus finmarchicus 的化学报警信号（桡足类酰胺）以实际浓度（0.6-6 pM）挑战时，S. arenicola 部分重新建立了昼夜摄食。相反，纤毛虫 Mesodinium rubrum 的昼夜摄食节律幅度不受桡足类酰胺的影响，尽管 24 小时的综合食物摄入量增加了约 23%。对于甲藻 Gyrodinium dominans 和 Karlodinium armiger，桡足类酰胺显著降低了它们昼夜摄食节律的幅度；仅在 G. dominans 中观察到对总日摄食有显著的正影响。最后，20 多年前分离的甲藻 Oxyrrhis marina 对桡足类酰胺的反应不一致，除了其 24 小时总摄入量平均增加 6%。我们的研究结果表明，桡足类的捕食风险影响海洋原生动物的昼夜摄食节律，并表明对捕食威胁的种特异性反应。
