Energetics, Growth, and Production of a Leaf-Shredding Stonefly in an Appalachian Mountain Stream

Publisher Website
Google Scholar
Abstract
Laboratory studies were conducted to measure growth, respiration, ingestion, and egestion for a leaf-shredding aquatic insect, Pteronarcys proteus (Plecoptera:Pteronarcyidae). These variables were measured for each of three cohorts found in a stream population, and all were a function of nymphal size and temperature. Relative growth rates (RGR) ranged from 0.031 to 0.0037 g g-1 day-1, with small nymphs growing fastest. Ingestion ranged from 5 to 40% of dry body weight per day. Respiration ranged from 330 to 980 μl O2 g-1 hr-1. Respiration, ingestion, and growth were highest for smallest nymphs and decreased with increasing size of nymphs. Assimilation efficiencies also followed this pattern, except for female nymphs, for which both ingestion and assimilation efficiencies did not decline. Total assimilation by a population of Pteronarcys proteus in a mountain stream was estimated at 119 kcal m-2 yr-1, accounted for primarily by the two oldest cohorts present. Energy flow was greatest at and after autumn leaf abscission and lowest after spring emergence of adults. Annual energetics of the nymphal population were: ingestion = 906, growth = 41, respiration = 78, and egestion = 828 kcal/m2. Annual production of three coexisting cohorts was 0.438 (Cohort 1), 3.158 (Cohort 2), and 4.182 (Cohort 3) g/m2. In the stream, instantaneous daily growth rates (IDGR) were highest for smallest nymphs and ranged from 0.018 to no detectable growth. Correlations between temperature and IDGR were not significant except for the youngest cohort, for which growth rates were highest during higher temperatures. Larger nymphs, however, grew fastest after leaf-fall when temperatures were lower. The data show that growth rates of small nymphs were influenced by temperature and growth rates of larger nymphs were affected by food supply. Simulation of growth of nymphs under food-unlimited conditions supported this conclusion. Pteronarcys proteus consumed an estimated 41-64% of the litterfall in the study stream.

This publication has 0 references indexed in Scilit: