Degradation, Growth, and Changes in Palatability of Leaves Colonized by Six Aquatic Hyphomycete Species

We followed the dynamics of aspen leaf degradation caused by six species of aquatic Hyphomycetes and examined the effect of fungal modification of leaves on feeding responses of caddisfly (Trichoptera) detritivores. All fungi caused weight loss, softening and increases in the ATP and nitrogen contents of leaves, although the timing of these changes varied among species. Articulospora inflata, Flagellospora curvula, Heliscus lugdunensis, and Tetrachaetum elegans grew and initiated leaf degradation early (5-10 da) while Anguillospora pseudolongissima exhibited a longer lag period (10-15 da). Lemonniera terrestris grew slowly and required a longer time (20 da) to cause comparable stages of degradation. We then determined feeding preferences of caddisfly larvae by measuring consumption after animals had fed on leaves from different treatment combinations (different fungal species at one incubation time or different incubations of one fungal species). Leaves generally became more palatable after the period of fungal growth, however, fungal species differed in their palatibility and in the period of time leaves remained at their optimum palatability. Leaves colonized by F. curvula and H. lugdunensis were more palatable than leaves colonized by other species. Results indicate that both fungal species composition and the duration of fungal colonization affect the palatability of leaves to caddisfly detritivores.