Active Uptake of Dissolved Organic Matter by Potamophylax cingulatus (Trichoptera) Larvae

Abstract
Active uptake of dissolved 14C-labeled glucose is demonstrated in the larva of the freshwater caddis P. cingulatus (Steph). (Limnephilidae). In laboratory experiments the caddis larvae had an uptake rate of circa 14.6 .mu.g g-1. After 2 h the concentration of glucose in P. cingulatus reached about 7 times that of the surrounding medium (based on volume), while the figure previously demonstrated for a freshwater bivalve was only 3 times in 24 h. Limnephilid larvae have well developed chloride epithelia, structures which facilitate osmoregulation and permit the larvae of some species to live in brackish environments. The significance of this structure for the uptake of dissolved organic matter is discussed. The glucose uptake is calculated to be circa 1% of the amount of energy assimilated from leaves which are the main food of the larvae.