We evaluated the effect of predation risk for larvae of Phylloicus (Trichoptera: Calamoceratidae) on leaf-litter consumption and case-building in experimental microcosms performing three Brazilian biomes: Amazon Forest, Atlantic Rainforest, and Brazilian Savanna (Cerrado). We hypothesized the following: (1) predation risk by fish would decrease the feeding rate but increase the sheltering activities of Phylloicus larvae, mainly in a high-stimulus treatment (visual and chemical cues from predators’ presence); and (2) when offered a resource with the same palatability, leaf consumption by Phylloicus larvae from Amazon Forest and Atlantic Rainforest will be higher than in those from the Savanna, independent of the predation risk. We found that larvae of Phylloicus species from the three biomes use the leaf disks in different proportions for case-building and consumption: Amazon Forest (case-building = 44% and consumption = 50%), Atlantic Rain Forest (60% and 36%), and Brazilian Savanna (32% and 26%). The larvae case-building and leaf consumption by Phylloicus were higher under predation than in the control treatment using data uncorrected by the biomass of the individual. On the other hand, case-building was not different among all treatments, and leaf consumption was lower under predation than in the control treatment when corrected by biomass. Our results indicate that predation risk can affect the behavior of Phylloicus due to a stress response to predator presence. Therefore, it might mean top-down effects on shredders during leaf-litter processing in Neotropical headwater streams. Besides, insectivorous fish could be the key group for functioning in these ecosystems.

我们评估了Phylloicus （毛翅目：Calamoceratidae）幼虫的捕食风险对执行三个巴西生物群落：亚马逊森林、大西洋雨林和巴西稀树草原（ Cerrado）的实验微观世界中落叶层消耗和案例构建的影响。我们假设如下：(1) 鱼类的捕食风险会降低Phylloicus幼虫的摄食率，但会增加它们的庇护活动，主要是在高刺激处理（捕食者存在的视觉和化学线索）中；(2) 当提供具有相同适口性的资源时，Phylloicus的叶子消耗量来自亚马逊森林和大西洋雨林的幼虫数量将高于来自稀树草原的幼虫，与捕食风险无关。我们发现来自三个生物群落的Phylloicus物种的幼虫以不同的比例使用叶盘进行案例构建和消费：亚马逊森林（案例构建 = 44% 和消费 = 50%），大西洋雨林（60% 和 36% )，以及巴西稀树草原（32% 和 26%）。Phylloicus的幼虫案例构建和叶子消耗使用未经个体生物量校正的数据，在捕食下比在对照处理中更高。另一方面，案例构建在所有处理之间没有差异，并且当通过生物量校正时，捕食下的叶子消耗低于对照处理。我们的结果表明，由于对捕食者存在的应激反应，捕食风险会影响Phylloicus的行为。因此，这可能意味着在新热带源头溪流的落叶处理过程中对切碎机产生自上而下的影响。此外，食虫鱼类可能是在这些生态系统中发挥作用的关键群体。