Chytrid fungal parasites are ubiquitous in aquatic ecosystems and infect a wide array of aquatic organisms, including all phytoplankton groups. In addition to their role as parasites, chytrids serve as food to zooplankton, thereby establishing an alternative trophic link between primary and secondary production in pelagic food webs, the so‐called mycoloop. We hypothesized that, in addition to the mycoloop, chytrid infection facilitates grazing of filamentous phytoplankton by rendering it more edible to zooplankton consumers through infection‐induced fragmentation. We undertook grazing assays to compare the ability of the key zooplankter Daphnia to graze on a filamentous cyanobacterium in the presence or absence of chytrid infection. A near doubling in mean clearance rates was consistently recorded when Daphnia were fed with infected cultures of the cyanobacterium as compared to uninfected ones. Infected filaments were shorter than noninfected ones, indicating that infection‐induced fragmentation undermines resistance of filamentous phytoplankton to grazing. We propose an extended conceptualization of the mycoloop that includes both direct effects (i.e., transfer via grazing of chytrid zoospores) and indirect effects (i.e., trophic upgrading and facilitated grazing on phytoplankton via fragmentation) of chytrid infection on trophic transfer at the base of pelagic food webs.

中文翻译：

---

真菌寄生虫感染丝状浮游植物会增强中上层食物网中的草食性

水生生态系统中普遍存在着壶兰真菌寄生虫，并感染了包括所有浮游植物群在内的各种水生生物。除了它们作为寄生虫的作用外，触角藻还可以作为浮游动物的食物，从而在远洋食物网中的初级生产和次级生产之间建立了一种替代性的营养联系，即所谓的霉菌环。我们假设，除了霉菌环以外，chytrid感染还可以通过感染引起的碎裂而使浮游植物的食用者更加食用，从而促进了丝状浮游植物的放牧。我们进行了放牧试验，以比较关键的浮游动物水蚤在存在或不存在糜蛋白酶感染的情况下在丝状蓝细菌上放牧的能力。持续记录的平均清除率几乎翻了一番。与未感染的相比，水蚤被感染了蓝细菌的培养物。感染的细丝比未感染的细丝短，表明感染引起的破碎破坏了丝状浮游植物对放牧的抵抗力。我们提议对霉菌环进行扩展的概念化，包括直接作用（即通过食糜的游丝孢子转移）和间接作用（即营养性的糜烂感染和浮游植物的碎裂促进浮游植物的放牧）对上层根部营养转移的乳糜菌感染。食物网。