Contribution of fungal biomass to the diet of a freshwater isopod (Lirceus sp.)

SUMMARY. 1. The direct contribution of fungal biomass to the carbon needs of a freshwater isopod (Lirceus sp.) was measured using 14C-labelled fungi on leaf material. 14C-glucose was added to fungus-inoculated leaf discs periodically throughout the growth of the fungus. Amount of label incorporated into fungal biomass, radioactivity appearing in Lirceus after feeding on labeled fungus and the standing stock of fungus were used to calculate incorporation of fungal C by the consumer.
2. Incorporation rates ranged from 0.06 to 70 ng fungal C mg wet wt isopod-1h-1. These rates of incorporation represent from 0.05 to 57% of C respired by the isopod.
3. Fungal C does not meet the carbon needs of this consumer and the role of fungi as modifiers of the leaf substrate may be more significant than their role as a food source.