Food preferences of earthworms for soil fungi

Soil fungi are considered to be an important food source for earthworms. Se lection experiments were carried out in order to study the preferences of e arthworm species for a variety of soil fungi. Nine fungal species (Cladospo rium cladosporioides, Rhizoctonia solani, Mucor sp., Tirchoderma viride, Fu sarium nivale, Phlebia radiata, Glaeophyllum trabeum, Coniophora puteana, C oriolus versicolor) were grown separately in centrifuge tubes on sterilized sand with potato dextrose. Tubes containing different fungal species, 8-9 per experiment, were arranged in a food choice arena. The preference for th e fungi of 5 different earthworm species (Lumbricus terrestris, Lumbricus c astaneus, Aporrectodea caliginosa, Aporrectodea rosea, Octolasion cyaneum) was tested by adding one specimen per chamber. Removal of sand from the tub es within 6 days was used as the indicator of preference by earthworms. The food preference of earthworms irrespective of ecological group followed a general pattern. F. nivale and C. cladosporioides were the preferred fungal species, followed by fast-growing species such as Mucor sp. and R. solani. In contrast, basidiomycetes were generally refused. The epigeic species L. rubellus had the strongest preference for a single fungal species, in cont rast the endogeic species A. rosea fed more evenly on different fungal spec ies. We conclude that early successional fungal species are used as cues by earthworms to detect fresh organic resources in soil.