FIGURE 4.14 Percentage of red-eyed treefrog egg mortality in laboratory-cultured egg masses when infected by a pure culture of an ascomyete fungus inoculm introduced by contaminated eggs, and from a natural population. Source: Data from Warkentin et al. (2001).

The role of fungi in aquatic ecosystems has been reviewed by Wong et al. (1998). They suggest that some 600 fungal species are associated with aquatic ecosystems and that their function ranges from saprotrophs to pathogens of both plants and animals. In aquatic ecosystems interactions among fungi and leaf-shredding fauna (Amphipoda, Isopoda, Diptera, Plecoptera, and Trichoptera) have been studied (Suberkropp, 1992). It has been suggested that fungal degradation of the leaf litter “conditions” the leaf material to make it more palatable for faunal grazing. These fungi alter the palatability of the litter resource, alter its chemical composition, and appear to increase its food value. Indeed, Bärlocher and Kendrick (1975) regard aquatic hyphomycetes as intermediaries in the energy flow in stream ecosystems. They showed that the amphipod Gammarus increased in weight faster in relation to the amount of food ingested when provided by the fungi Humicola, Anguillospora, Clavariopsis, Tricladium, or Fusarium, compared to a diet of elm or maple leaves.