Laboratory of Ecophysiology and Toxicology of Cyanobacteria, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro, 21949-902, Brazil.
Laboratory of Evaluation and Promotion of Environmental Health, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, 21040-360, Brazil.
J Chem Ecol. 2021 Nov;47(10-11):847-858. doi: 10.1007/s10886-021-01315-5. Epub 2021 Sep 27.
Cyanobacteria are photosynthetic microorganisms that compose phytoplankton and therefore have a trophic relationship with zooplankton, which represent an important link for energy flux in aquatic food webs. Several species can form blooms and produce bioactive metabolites known as cyanotoxins. However, the ecological and adaptative role of these toxins are still under debate. Many studies have addressed the cyanotoxins' function in defense against herbivory when grazing pressure by zooplankton plays a role in phytoplankton top-down control. Thus, the present study evaluated the ecophysiological responses of the cyanobacterial strain Microcystis aeruginosa NPLJ-4 underlying the chemical induced defense against the cladoceran Daphnia gessneri. Exposure to predator infochemicals consisted of cultures established in ASM-1 medium prepared in a filtrate from a culture of adults of D. gessneri at an environmentally relevant density. Daphnia infochemicals promoted a significant increase in toxin production by M. aeruginosa. However, no differences in growth were observed, despite a significant increase in both maximum photosynthetic efficiency and electron transport rate in response to zooplankton. Additionally, there was no significant variation in the production of exopolysaccharides. Overall, although a grazer-induced defense response was demonstrated, there were no effects on M. aeruginosa fitness, which maintained its growth in the presence of Daphnia alarm cues.
蓝藻是能进行光合作用的微生物，构成浮游植物，因此与浮游动物有营养关系，浮游动物是水生食物网中能量流动的重要环节。一些蓝藻物种可以形成水华，并产生生物活性代谢物，即蓝藻毒素。然而，这些毒素的生态和适应性作用仍存在争议。许多研究都探讨了蓝藻毒素在防御食草动物方面的作用，当浮游动物的摄食压力对浮游植物的自上而下控制起作用时。因此，本研究评估了在化学生物防御下，蓝藻菌株铜绿微囊藻 NPLJ-4 的生理生态反应，这种防御是针对枝角类动物大型溞的。暴露于捕食者信息素包括在一个与环境相关密度的大型溞成体培养物滤液中制备的 ASM-1 培养基中建立的培养物。大型溞信息素促进了铜绿微囊藻毒素的大量产生。然而，尽管对浮游动物的最大光合作用效率和电子传递率都有显著的增加，但生长没有差异。此外，胞外多糖的产生也没有显著变化。总的来说，尽管证明了存在由食草动物诱导的防御反应，但这对铜绿微囊藻的适应性没有影响，因为在有大型溞警报信号的情况下，它仍能维持生长。
