Factors affecting food utilization by a leaf shredding aquatic insect: leaf species and conditioning time

Abstract

Gravimetric feeding studies were used to examine the feeding strategy of Pteronarcys proteus (Plecoptera) using unconditioned, 1 month conditioned, and 2 month conditioned deciduous leaves of four species (white oak, red maple, black locust, dogwood). Assimilation efficiencies of Pteronarcys nymphs feeding on unconditioned and conditioned leaf material ranged from 13.4 to 21.9% AFDW of leaf material indicating that Pteronarcys was able to digest and assimilate leaf material. Assimilation efficiencies did not change as leaf material conditioned which suggests that assimilation efficiency does not accurately reflect changes in detrital food quality. However, as leaves conditioned, the ingestion rate of Pteronarcys nymphs accelerated. Rates at which dogwood and locust leaves were ingested peaked after 1 month, then declined with a second month of conditioning. Rates at which maple and oak leaves were ingested increased significantly with 2 months of conditioning. Assimilation rates of Pteronarcys nymphs varied in a pattern similar to ingestion rates. This reflects the importance of ingestion rate in the feeding response of Pteronarcys.